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Magick::Image Class
Magick::Image Class
Quick Contents
Image is the primary object in Magick++ and represents
a single image frame (see design ). The STL interface must be used to operate on
image sequences or images (e.g. of format GIF, TIFF, MIFF, Postscript,
& MNG) which are comprized of multiple image frames. Individual
frames of a multi-frame image may be requested by adding array-style
notation to the end of the file name (e.g. "animation.gif[3]" retrieves
the fourth frame of a GIF animation. Various image manipulation
operations may be applied to the image. Attributes may be set on the
image to influence the operation of the manipulation operations. The Pixels class provides low-level access to image
pixels. As a convenience, including <Magick++.h>
is sufficient in order to use the complete Magick++ API. The Magick++
API is enclosed within the Magick namespace so you must either
add the prefix " Magick:: " to each class/enumeration name or add
the statement " using namespace Magick;" after including the Magick++.h
header.
The preferred way to allocate Image objects is via automatic
allocation (on the stack). There is no concern that allocating Image
objects on the stack will excessively enlarge the stack since Magick++
allocates all large data objects (such as the actual image data) from
the heap. Use of automatic allocation is preferred over explicit
allocation (via new) since it is much less error prone and
allows use of C++ scoping rules to avoid memory leaks. Use of automatic
allocation allows Magick++ objects to be assigned and copied just like
the C++ intrinsic data types (e.g. 'int '), leading to clear and
easy to read code. Use of automatic allocation leads to naturally
exception-safe code since if an exception is thrown, the object is
automatically deallocated once the stack unwinds past the scope of the
allocation (not the case for objects allocated via new ).
Image is very easy to use. For example, here is a the source to a
program which reads an image, crops it, and writes it to a new file (the
exception handling is optional but strongly recommended):
#include <Magick++.h>
#include <iostream>
using namespace std;
using namespace Magick;
int main(int argc,char **argv)
{
// Construct the image object.
Seperating image construction from the
// the read operation ensures that a
failure to read the image file
// doesn't render the image object
useless.
Image image;
try {
// Read a file into
image object
image.read( "girl.gif" );
// Crop the image to
specified size (width, height, xOffset, yOffset)
image.crop(
Geometry(100,100, 100, 100) );
// Write the image to
a file
image.write( "x.gif" );
}
catch( Exception &error_ )
{
cout
<< "Caught exception: " << error_.what() << endl;
return 1;
}
return 0;
}
The following is the source to a program which illustrates the use of
Magick++'s efficient reference-counted assignment and copy-constructor
operations which minimize use of memory and eliminate unncessary copy
operations (allowing Image objects to be efficiently assigned, and
copied into containers). The program accomplishes the
following:
- Read master image.
- Assign master image to second image.
- Zoom second image to the size 640x480.
- Assign master image to a third image.
- Zoom third image to the size 800x600.
- Write the second image to a file.
- Write the third image to a file.
#include <Magick++.h>
#include <iostream>
using namespace std;
using namespace Magick;
int main(int argc,char **argv)
{
Image
master("horse.jpg");
Image second = master;
second.zoom("640x480");
Image third = master;
third.zoom("800x600");
second.write("horse640x480.jpg");
third.write("horse800x600.jpg");
return 0;
}
During the entire operation, a maximum of three images exist in memory
and the image data is never copied.
The following is the source for another simple program which creates
a 100 by 100 pixel white image with a red pixel in the center and
writes it to a file:
#include <Magick++.h>
using namespace std;
using namespace Magick;
int main(int argc,char **argv)
{
Image image( "100x100",
"white" );
image.pixelColor( 49,
49, "red" );
image.write(
"red_pixel.png" );
return 0;
}
If you wanted to change the color image to grayscale, you could add the
lines:
image.quantizeColorSpace( GRAYColorspace );
image.quantizeColors( 256
);
image.quantize( );
or, more simply:
image.type(
GrayscaleType );
prior to writing the image.
BLOBs
While encoded images (e.g. JPEG) are most often written-to and
read-from a disk file, encoded images may also reside in memory. Encoded
images in memory are known as BLOBs (Binary Large OBjects) and may be
represented using the Blob class. The encoded
image may be initially placed in memory by reading it directly from a
file, reading the image from a database, memory-mapped from a disk
file, or could be written to memory by Magick++. Once the encoded image
has been placed within a Blob, it may be read into a Magick++ Image via
a constructor or read()
. Likewise, a Magick++ image may be written to a Blob via write() .
An example of using Image to write to a Blob follows:
#include <Magick++.h>
using namespace std;
using namespace Magick;
int main(int argc,char **argv)
{
// Read GIF file from
disk
Image image(
"giraffe.gif" );
// Write to BLOB in
JPEG format
Blob blob;
image.magick( "JPEG" )
// Set JPEG output format
image.write( &blob );
[ Use BLOB data (in
JPEG format) here ]
return 0;
}
likewise, to read an image from a Blob, you could use one of the
following examples:
[ Entry condition for the following examples
is that data is pointer to encoded image data and length
represents the size of the data ]
Blob blob( data, length );
Image image( blob );
or
Blob blob( data, length );
Image image;
image.read( blob);
some images do not contain their size or format so the size and format
must be specified in advance:
Blob blob( data, length );
Image image;
image.size( "640x480")
image.magick( "RGBA" );
image.read( blob);
Constructors
Image may be constructed in a number of ways. It may be constructed
from a file, a URL, or an encoded image (e.g. JPEG) contained in an
in-memory BLOB . The available Image
constructors are shown in the following table:
Image Constructors
|
Signature
|
Description
|
| const std::string &imageSpec_ |
Construct Image by reading from file or URL
specified by imageSpec_. Use array notation (e.g. filename[9])
to select a specific scene from a multi-frame image. |
| const Geometry &size_, const Color &color_ |
Construct a blank image canvas of specified
size and color |
| const Blob &blob_ |
Construct Image by reading from
encoded image data contained in an in-memory BLOB
. Depending on the constructor arguments, the Blob size
, depth , magick (format) may
also be specified. Some image formats require that size be specified.
The default ImageMagick uses for depth depends on the compiled-in
Quantum size (8 or 16). If ImageMagick's Quantum size does not
match that of the image, the depth may need to be specified.
ImageMagick can usually automatically detect the image's format.
When a format can't be automatically detected, the format (magick ) must be specified. |
| const Blob
&blob_, const Geometry &size_ |
| const Blob
&blob_, const Geometry &size,
unsigned int depth |
| const Blob
&blob_, const Geometry &size,
unsigned int depth_, const string &magick_ |
| const Blob
&blob_, const Geometry &size, const
string &magick_ |
const unsigned int width_,
const unsigned int height_,
std::string map_,
const
StorageType type_,
const void *pixels_ |
Construct a new Image based on an array of
image pixels. The pixel data must be in scanline order top-to-bottom.
The data can be character, short int, integer, float, or double. Float
and double require the pixels to be normalized [0..1]. The other types
are [0..QuantumRange]. For example, to create a 640x480 image from
unsigned red-green-blue character data, use
Image image( 640, 480, "RGB",
0, pixels );
The parameters are as follows:
| width_ |
Width in pixels of the image. |
| height_ |
Height in pixels of the image. |
| map_ |
This character string can be any
combination or order of R = red, G = green, B = blue, A = alpha, C =
cyan, Y = yellow M = magenta, and K = black. The ordering reflects the
order of the pixels in the supplied pixel array. |
| type_ |
Pixel
storage type (CharPixel, ShortPixel, IntegerPixel, FloatPixel, or
DoublePixel) |
| pixels_ |
This array of values contain the pixel
components as defined by the map_ and type_ parameters. The length of
the arrays must equal the area specified by the width_ and height_
values and type_ parameters. |
|
Image Manipulation Methods
Image supports access to all the single-image (versus image-list)
manipulation operations provided by the ImageMagick library. If you
must process a multi-image file (such as an animation), the STL interface , which provides a multi-image
abstraction on top of Image, must be used.
Image manipulation methods are very easy to use. For example:
Image image;
image.read("myImage.tiff");
image.addNoise(GaussianNoise);
image.write("myImage.tiff");
adds gaussian noise to the image file "myImage.tiff".
The operations supported by Image are shown in the following table:
Image Image Manipulation Methods
| Method |
Signature(s) |
Description |
|
|
unsigned int width, unsigned
int height, unsigned offset = 0
|
Apply adaptive thresholding to
the image. Adaptive thresholding is useful if the ideal threshold level
is not known in advance, or if the illumination gradient is not constant
across the image. Adaptive thresholding works by evaulating the mean
(average) of a pixel region (size specified by width and height)
and using the mean as the thresholding value. In order to remove
residual noise from the background, the threshold may be adjusted by
subtracting a constant offset (default zero) from the mean to
compute the threshold.
|
|
addNoise
|
NoiseType
noiseType_ |
Add noise to image with specified noise type. |
affineTransform
|
const DrawableAffine
&affine
|
Transform image by
specified affine (or free transform) matrix.
|
|
annotate
|
const std::string &text_, const Geometry &location_ |
Annotate using specified text, and placement
location |
| string text_, const Geometry
&boundingArea_, GravityType
gravity_ |
Annotate using specified text, bounding area,
and placement gravity. If boundingArea_ is invalid, then
bounding area is entire image. |
| const std::string &text_, const Geometry &boundingArea_, GravityType gravity_, double
degrees_, |
Annotate with text using specified text,
bounding area, placement gravity, and rotation. If boundingArea_
is invalid, then bounding area is entire image. |
| const std::string &text_, GravityType gravity_ |
Annotate with text (bounding area is entire
image) and placement gravity. |
|
blur
|
const double radius_ = 1, const double sigma_
= 0.5 |
Blur image. The radius_ parameter
specifies the radius of the Gaussian, in pixels, not counting the center
pixel. The sigma_ parameter specifies the standard
deviation of the Laplacian, in pixels. |
|
border
|
const Geometry
&geometry_ = "6x6+0+0" |
Border image (add border to image). The
color of the border is specified by the borderColor attribute. |
|
channel
|
ChannelType
layer_ |
Extract channel from image. Use this option
to extract a particular channel from the image. MatteChannel
for example, is useful for extracting the opacity values
from an image. |
|
charcoal
|
const double radius_ = 1, const double sigma_
= 0.5 |
Charcoal effect image (looks like charcoal
sketch). The radius_ parameter specifies the radius of the
Gaussian, in pixels, not counting the center pixel. The sigma_
parameter specifies the standard deviation of the Laplacian, in pixels. |
|
chop
|
const Geometry
&geometry_ |
Chop image (remove vertical or horizontal
subregion of image) |
|
colorize
|
const unsigned int opacityRed_, const
unsigned int opacityGreen_, const unsigned int opacityBlue_, const
Color &penColor_ |
Colorize image with pen color, using
specified percent opacity for red, green, and blue quantums. |
| const unsigned int opacity_, const Color
&penColor_ |
Colorize image with pen color, using
specified percent opacity. |
|
comment
|
const string &comment_ |
Comment image (add comment string to
image). By default, each image is commented with its file name.
Use this method to assign a specific comment to the
image. Optionally you can include the image filename, type,
width, height, or other image attributes by embedding special format characters. |
compare
|
const Image &reference_
|
Compare current image with
another image. Sets meanErrorPerPixel , normalizedMaxError , and normalizedMeanError in the current
image. False is returned if the images are identical. An ErrorOption
exception is thrown if the reference image columns, rows, colorspace, or
matte differ from the current image.
|
|
composite
|
const Image
&compositeImage_, int xOffset_, int yOffset_, CompositeOperator
compose_ = InCompositeOp |
Compose an image onto the current image at
offset specified by xOffset_, yOffset_ using the
composition algorithm specified by compose_. |
| const Image
&compositeImage_, const Geometry
&offset_, CompositeOperator
compose_ = InCompositeOp |
Compose an image onto the current image at
offset specified by offset_ using the composition algorithm
specified by compose_ . |
| const Image
&compositeImage_, GravityType
gravity_, CompositeOperator
compose_ = InCompositeOp |
Compose an image onto the current image with
placement specified by gravity_ using the composition algorithm
specified by compose_. |
|
contrast
|
unsigned int sharpen_ |
Contrast image (enhance intensity differences
in image) |
|
convolve
|
unsigned int order_, const double *kernel_ |
Convolve image. Applies a user-specfied
convolution to the image. The order_ parameter represents the
number of columns and rows in the filter kernel, and kernel_
is a two-dimensional array of doubles representing the convolution
kernel to apply. |
|
crop
|
const Geometry
&geometry_ |
Crop image (subregion of original image) |
|
cycleColormap
|
int amount_ |
Cycle image colormap |
|
despeckle
|
void |
Despeckle image (reduce speckle noise) |
|
display
|
void |
Display image on screen.
Caution: if
an image format is is not compatible with the display visual (e.g.
JPEG on a colormapped display) then the original image will be
altered. Use a copy of the original if this is a problem. |
|
draw
|
const Drawable
&drawable_ |
Draw shape or text on image. |
| const std::list<Drawable
> &drawable_ |
Draw shapes or text on image using a set of
Drawable objects contained in an STL list. Use of this method improves
drawing performance and allows batching draw objects together in a
list for repeated use. |
|
edge
|
unsigned int radius_ = 0.0 |
Edge image (hilight edges in image).
The radius is the radius of the pixel neighborhood.. Specify a radius
of zero for automatic radius selection. |
|
emboss
|
const double radius_ = 1, const double sigma_
= 0.5 |
Emboss image (hilight edges with 3D effect).
The radius_ parameter specifies the radius of the Gaussian, in
pixels, not counting the center pixel. The sigma_
parameter specifies the standard deviation of the Laplacian, in pixels. |
|
enhance
|
void |
Enhance image (minimize noise) |
|
equalize
|
void |
Equalize image (histogram equalization) |
|
erase
|
void |
Set all image pixels to the current
background color. |
|
flip
|
void |
Flip image (reflect each scanline in the
vertical direction) |
floodFill-
Color
|
unsigned int x_, unsigned int y_, const Color &fillColor_ |
Flood-fill color across pixels
that match the color of the target pixel and are neighbors of the
target pixel. Uses current fuzz setting when determining color match. |
| const Geometry
&point_, const Color &fillColor_ |
| unsigned int x_, unsigned int y_, const Color &fillColor_, const Color
&borderColor_ |
Flood-fill color across pixels
starting at target-pixel and stopping at pixels matching specified
border color. Uses current fuzz setting when determining color match. |
| const Geometry
&point_, const Color &fillColor_, const Color &borderColor_ |
| floodFillOpacity |
const long x_, const long y_, const unsigned
int opacity_, const PaintMethod method_ |
Floodfill pixels matching color (within fuzz
factor) of target pixel(x,y) with replacement opacity value using method. |
floodFill-
Texture
|
unsigned int x_, unsigned int y_, const
Image &texture_ |
Flood-fill texture across pixels
that match the color of the target pixel and are neighbors of the
target pixel. Uses current fuzz setting when determining color match. |
| const Geometry
&point_, const Image &texture_ |
| unsigned int x_, unsigned int y_, const Image
&texture_, const Color &borderColor_ |
Flood-fill texture across pixels
starting at target-pixel and stopping at pixels matching specified
border color. Uses current fuzz setting when determining color match. |
| const Geometry
&point_, const Image &texture_, const Color
&borderColor_ |
|
flop
|
void |
Flop image (reflect each scanline in the
horizontal direction) |
|
frame
|
const Geometry
&geometry_ = "25x25+6+6" |
Add decorative frame around image |
| unsigned int width_, unsigned int height_,
int x_, int y_, int innerBevel_ = 0, int outerBevel_ = 0 |
|
gamma
|
double gamma_ |
Gamma correct image (uniform red, green, and
blue correction). |
| double gammaRed_, double gammaGreen_, double
gammaBlue_ |
Gamma correct red, green, and blue channels
of image. |
|
gaussianBlur
|
const double width_, const double sigma_ |
Gaussian blur image. The number of neighbor
pixels to be included in the convolution mask is specified by
'width_'. For example, a width of one gives a (standard) 3x3
convolution mask. The standard deviation of the gaussian bell curve is
specified by 'sigma_'. |
|
implode
|
const double factor_ |
Implode image (special effect) |
|
label
|
const string &label_ |
Assign a label to an image. Use this option
to assign a specific label to the image. Optionally
you can include the image filename, type, width, height, or scene
number in the label by embedding
special format characters. If the first character of string is @, the
image label is read from a file titled by the remaining characters in
the string. When converting to Postscript, use this option to
specify a header string to print above the image. |
level
|
const double black_point,
const double white_point, const double mid_point=1.0
|
Level image. Adjust the
levels of the image by scaling the colors falling between specified
white and black points to the full available quantum range. The
parameters provided represent the black, mid (gamma), and white
points. The black point specifies the darkest color in the image.
Colors darker than the black point are set to zero. Mid point (gamma)
specifies a gamma correction to apply to the image. White point
specifies the lightest color in the image. Colors brighter than
the white point are set to the maximum quantum value. The black and
white point have the valid range 0 to QuantumRange while mid (gamma) has a
useful range of 0 to ten.
|
levelChannel
|
const ChannelType
channel, const double black_point, const double white_point, const
double mid_point=1.0
|
Level image channel.
Adjust the levels of the image channel by scaling the values falling
between specified white and black points to the full available quantum
range. The parameters provided represent the black, mid (gamma), and
white points. The black point specifies the darkest color in the image.
Colors darker than the black point are set to zero. Mid point (gamma)
specifies a gamma correction to apply to the image. White point
specifies the lightest color in the image. Colors brighter than the
white point are set to the maximum quantum value. The black and white
point have the valid range 0 to QuantumRange while mid (gamma) has a useful
range of 0 to ten.
|
|
magnify
|
void |
Magnify image by integral size |
|
map
|
const Image &mapImage_ , bool dither_ =
false |
Remap image colors with closest color from
reference image. Set dither_ to true in to apply Floyd/Steinberg
error diffusion to the image. By default, color reduction chooses an
optimal set of colors that best represent the original
image. Alternatively, you can choose a
particular set of colors from an image file
with this option. |
|
matteFloodfill
|
const Color
&target_, const unsigned int opacity_, const int x_, const int
y_, PaintMethod method_ |
Floodfill designated area with a replacement
opacity value. |
| medianFilter |
const double radius_ = 0.0 |
Filter image by replacing each pixel
component with the median color in a circular neighborhood |
|
minify
|
void |
Reduce image by integral size |
| modifyImage |
void |
Prepare to update image. Ensures that there
is only one reference to the underlying image so that the underlying
image may be safely modified without effecting previous generations of
the image. Copies the underlying image to a new image if necessary. |
|
modulate
|
double brightness_, double saturation_,
double hue_ |
Modulate percent hue, saturation, and
brightness of an image. Modulation of saturation and brightness is as a
ratio of the current value (1.0 for no change). Modulation of hue is an
absolute rotation of -180 degrees to +180 degrees from the current
position corresponding to an argument range of 0 to 2.0 (1.0 for no
change). |
|
negate
|
bool grayscale_ = false |
Negate colors in image. Replace every
pixel with its complementary color (white becomes black, yellow becomes
blue, etc.). Set grayscale to only negate grayscale values in
image. |
|
normalize
|
void |
Normalize image (increase contrast by
normalizing the pixel values to span the full range of color values). |
|
oilPaint
|
unsigned int radius_ = 3 |
Oilpaint image (image looks like oil painting) |
|
opacity
|
unsigned int opacity_ |
Set or attenuate the opacity channel in the
image. If the image pixels are opaque then they are set to the specified
opacity value, otherwise they are blended with the supplied opacity
value. The value of opacity_ ranges from 0 (completely opaque) to QuantumRange
. The defines OpaqueOpacity and TransparentOpacity are
available to specify completely opaque or completely transparent,
respectively. |
|
opaque
|
const Color
&opaqueColor_, const Color &penColor_ |
Change color of pixels matching opaqueColor_
to specified penColor_. |
|
ping
|
const std::string &imageSpec_ |
Ping is similar to read
except only enough of the image is read to determine the image columns,
rows, and filesize. The columns , rows , and fileSize
attributes are valid after invoking ping. The image data is not
valid after calling ping. |
| const Blob &blob_ |
process
|
std::string name_,
const int argc_, char **argv_
|
Execute the named
process module, passing any arguments via an argument vector, with argc_
specifying the number of arguments in the vector, and argv_ passing the
address of an array of null-terminated C strings which constitute the
argument vector. An exception is thrown if the requested process module
does not exist, fails to load, or fails during execution.
|
|
quantize
|
bool measureError_ = false |
Quantize image (reduce number of colors). Set
measureError_ to true in order to calculate error attributes. |
|
raise
|
const Geometry
&geometry_ = "6x6+0+0", bool raisedFlag_ = false |
Raise image (lighten or darken the edges of
an image to give a 3-D raised or lowered effect) |
|
read
|
const string &imageSpec_ |
Read image into current object |
| const Geometry
&size_, const std::string &imageSpec_ |
Read image of specified size into current
object. This form is useful for images that do not specifiy their size
or to specify a size hint for decoding an image. For example, when
reading a Photo CD, JBIG, or JPEG image, a size request causes the
library to return an image which is the next resolution greater or
equal to the specified size. This may result in memory and time savings. |
| const Blob &blob_ |
Read encoded image of specified
size from an in-memory BLOB into current
object. Depending on the method arguments, the Blob size, depth, and
format may also be specified. Some image formats require that size be
specified. The default ImageMagick uses for depth depends on its
Quantum size (8 or 16). If ImageMagick's Quantum size does not
match that of the image, the depth may need to be specified.
ImageMagick can usually automatically detect the image's format. When
a format can't be automatically detected, the format must be specified. |
| const Blob
&blob_, const Geometry &size_ |
| const Blob
&blob_, const Geometry &size_,
unsigned int depth_ |
| const Blob
&blob_, const Geometry &size_,
unsigned short depth_, const string &magick_ |
| const Blob
&blob_, const Geometry &size_, const
string &magick_ |
| const unsigned int width_, const unsigned int
height_, std::string map_, const StorageType type_, const void *pixels_ |
Read image based on an array of image pixels.
The pixel data must be in scanline order top-to-bottom. The data can be
character, short int, integer, float, or double. Float and double
require the pixels to be normalized [0..1]. The other types are
[0..QuantumRange]. For example, to create a 640x480 image from
unsigned red-green-blue character data, use
image.read( 640, 480, "RGB", 0,
pixels );
The parameters are as follows:
| width_ |
Width in pixels of the image. |
| height_ |
Height in pixels of the image. |
| map_ |
This character string can be any
combination or order of R = red, G = green, B = blue, A = alpha, C =
cyan, Y = yellow M = magenta, and K = black. The ordering reflects the
order of the pixels in the supplied pixel array. |
| type_ |
Pixel storage type (CharPixel,
ShortPixel, IntegerPixel, FloatPixel, or DoublePixel) |
| pixels_ |
This array of values contain the pixel
components as defined by the map_ and type_ parameters. The length of
the arrays must equal the area specified by the width_ and height_
values and type_ parameters. |
|
|
reduceNoise
|
void |
Reduce noise in image using a
noise peak elimination filter. |
| unsigned int order_ |
|
roll
|
int columns_, int rows_ |
Roll image (rolls image vertically and
horizontally) by specified number of columnms and rows) |
|
rotate
|
double degrees_ |
Rotate image counter-clockwise by specified
number of degrees. |
|
sample
|
const Geometry
&geometry_ |
Resize image by using pixel sampling algorithm |
|
scale
|
const Geometry
&geometry_ |
Resize image by using simple ratio algorithm |
|
segment
|
double clusterThreshold_ = 1.0,
double smoothingThreshold_ = 1.5 |
Segment (coalesce similar image components)
by analyzing the histograms of the color components and identifying
units that are homogeneous with the fuzzy c-means technique. Also uses quantizeColorSpace
and verbose image attributes. Specify clusterThreshold_ ,
as the number of pixels each cluster must exceed
the cluster threshold to be considered valid. SmoothingThreshold_
eliminates noise in the second derivative of the histogram. As the
value is increased, you can expect a smoother
second derivative. The default is 1.5. |
|
shade
|
double azimuth_ = 30, double elevation_ = 30,
bool colorShading_ = false |
Shade image using distant light source.
Specify azimuth_ and elevation_ as the
position of the light source. By default, the shading
results as a grayscale image.. Set colorShading_ to true to
shade the red, green, and blue components of the image. |
|
sharpen
|
const double radius_ = 1, const double sigma_
= 0.5 |
Sharpen pixels in image. The radius_
parameter specifies the radius of the Gaussian, in pixels, not counting
the center pixel. The sigma_ parameter specifies the
standard deviation of the Laplacian, in pixels. |
|
shave
|
const Geometry &geometry_ |
Shave pixels from image edges. |
|
shear
|
double xShearAngle_, double yShearAngle_ |
Shear image (create parallelogram by sliding
image by X or Y axis). Shearing slides one edge of an image along
the X or Y axis, creating a
parallelogram. An X direction shear slides an edge along the X
axis, while a Y direction shear slides
an edge along the Y axis. The amount of the shear is controlled
by a shear angle. For X direction shears, x
degrees is measured relative to the Y axis, and similarly, for Y
direction shears y degrees is measured relative to the X
axis. Empty triangles left over from shearing the image are
filled with the color defined as borderColor. |
|
solarize
|
double factor_ = 50.0 |
Solarize image (similar to effect seen when
exposing a photographic film to light during the development process) |
|
spread
|
unsigned int amount_ = 3 |
Spread pixels randomly within image by
specified amount |
|
stegano
|
const Image &watermark_ |
Add a digital watermark to the image (based
on second image) |
|
stereo
|
const Image &rightImage_ |
Create an image which appears in stereo when
viewed with red-blue glasses (Red image on left, blue on right) |
|
swirl
|
double degrees_ |
Swirl image (image pixels are rotated by
degrees) |
|
texture
|
const Image &texture_ |
Layer a texture on pixels matching image
background color. |
|
threshold
|
double threshold_ |
Threshold image |
|
transform
|
const Geometry
&imageGeometry_ |
Transform image based on image
and crop geometries. Crop geometry is optional. |
| const Geometry
&imageGeometry_, const Geometry
&cropGeometry_ |
|
transparent
|
const Color
&color_ |
Add matte image to image, setting pixels
matching color to transparent. |
|
trim
|
void |
Trim edges that are the background color from
the image. |
|
unsharpmask
|
double radius_, double sigma_, double
amount_, double threshold_ |
Replace image with a sharpened version of the
original image using the unsharp mask algorithm. The radius_
parameter specifies the radius of the Gaussian, in pixels, not
counting the center pixel. The sigma_ parameter specifies the
standard deviation of the Gaussian, in pixels. The amount_
parameter specifies the percentage of the difference between the
original and the blur image that is added back into the original. The threshold_
parameter specifies the threshold in pixels needed to apply the
diffence amount. |
|
wave
|
double amplitude_ = 25.0, double wavelength_
= 150.0 |
Alter an image along a sine wave. |
|
write
|
const string &imageSpec_ |
Write image to a file using filename imageSpec_
.
Caution: if
an image format is selected which is capable of supporting fewer
colors than the original image or quantization has been requested, the
original image will be quantized to fewer colors. Use a copy of the
original if this is a problem. |
| Blob *blob_ |
Write image to a in-memory BLOB stored in blob_. The magick_
parameter specifies the image format to write (defaults to magick ). The depth_ parameter species the image
depth (defaults to depth ).
Caution: if
an image format is selected which is capable of supporting fewer
colors than the original image or quantization has been requested, the
original image will be quantized to fewer colors. Use a copy of the
original if this is a problem. |
| Blob *blob_,
std::string &magick_ |
| Blob *blob_,
std::string &magick_, unsigned int depth_ |
| const int x_, const int y_, const unsigned
int columns_, const unsigned int rows_, const std::string &map_,
const StorageType type_, void *pixels_ |
Write pixel data into a buffer you supply.
The data is saved either as char, short int, integer, float or double
format in the order specified by the type_ parameter. For example, we
want to extract scanline 1 of a 640x480 image as character data in
red-green-blue order:
image.write(0,0,640,1,"RGB",0,pixels);
The parameters are as follows:
| x_ |
Horizontal ordinate of left-most
coordinate of region to extract. |
| y_ |
Vertical ordinate of top-most
coordinate of region to extract. |
| columns_ |
Width in pixels of the region to
extract. |
| rows_ |
Height in pixels of the region to
extract. |
| map_ |
This character string can be any
combination or order of R = red, G = green, B = blue, A = alpha, C =
cyan, Y = yellow, M = magenta, and K = black. The ordering reflects
the order of the pixels in the supplied pixel array. |
| type_ |
Pixel storage type (CharPixel,
ShortPixel, IntegerPixel, FloatPixel, or DoublePixel) |
| pixels_ |
This array of values contain the pixel
components as defined by the map_ and type_ parameters. The length of
the arrays must equal the area specified by the width_ and height_
values and type_ parameters. |
|
|
zoom
|
const Geometry
&geometry_ |
Zoom image to specified size. |
Image Attributes
Image attributes are set and obtained via methods in Image. Except for
methods which accept pointer arguments (e.g. chromaBluePrimary)
all methods return attributes by value.
Image attributes are easily used. For example, to set the resolution
of the TIFF file "file.tiff" to 150 dots-per-inch (DPI) in both the
horizontal and vertical directions, you can use the following example
code:
string filename("file.tiff");
Image image;
image.read(filename);
image.resolutionUnits(PixelsPerInchResolution);
image.density(Geometry(150,150));
// could also use image.density("150x150")
image.write(filename)
The supported image attributes and the method arguments required to
obtain them are shown in the following table:
Image Attributes
|
Function
|
Type
|
Get Signature
|
Set Signature
|
Description
|
|
adjoin
|
bool |
void |
bool flag_ |
Join images into a single multi-image file. |
|
antiAlias
|
bool |
void |
bool flag_ |
Control antialiasing of rendered Postscript
and Postscript or TrueType fonts. Enabled by default. |
animation-
Delay
|
unsigned int (0 to 65535) |
void |
unsigned int delay_ |
Time in 1/100ths of a second (0 to 65535)
which must expire before displaying the next image in an animated
sequence. This option is useful for regulating the animation of a
sequence of GIF images within Netscape. |
animation-
Iterations
|
unsigned int |
void |
unsigned int iterations_ |
Number of iterations to loop an animation
(e.g. Netscape loop extension) for. |
attribute
|
string
|
const
std::string name_
|
const
std::string name_, const std::string value_ |
An arbitrary named
image attribute. Any number of named attributes may be attached to the
image. For example, the image comment is a named image attribute with
the name "comment". EXIF tags are attached to the image as named
attributes. Use the syntax "[EXIF:<tag>]" to request an EXIF tag
similar to "[EXIF:DateTime]".
|
background-
Color
|
Color |
void |
const Color
&color_ |
Image background color |
background-
Texture
|
string |
void |
const string &texture_ |
Image file name to use as the background
texture. Does not modify image pixels. |
|
baseColumns
|
unsigned int |
void |
|
Base image width (before transformations) |
|
baseFilename
|
string |
void |
|
Base image filename (before transformations) |
|
baseRows
|
unsigned int |
void |
|
Base image height (before transformations) |
|
borderColor
|
Color |
void |
const Color
&color_ |
Image border color |
| boundingBox |
Geometry |
void |
|
Return smallest bounding box enclosing
non-border pixels. The current fuzz value is used when discriminating
between pixels. This is the crop bounding box used by
crop(Geometry(0,0)). |
|
boxColor
|
Color |
void |
const Color
&boxColor_ |
Base color that annotation text is rendered
on. |
| cacheThreshold |
unsigned int |
|
const int |
Pixel cache threshold in megabytes. Once this
threshold is exceeded, all subsequent pixels cache operations are
to/from disk. This is a static method and the attribute it sets is
shared by all Image objects. |
channelDepth
|
unsigned
int
|
const
ChannelType channel_
|
const ChannelType
channel_, const unsigned int depth_
|
Channel modulus depth.
The channel modulus depth represents the minimum number of bits required
to support the channel without loss. Setting the channel's modulus depth
modifies the channel (i.e. discards resolution) if the requested modulus
depth is less than the current modulus depth, otherwise the channel is
not altered. There is no attribute associated with the modulus depth so
the current modulus depth is obtained by inspecting the pixels. As a
result, the depth returned may be less than the most recently set
channel depth. Subsequent image processing may result in increasing the
channel depth.
|
chroma-
BluePrimary
|
double x & y |
double *x_, double *y_ |
double x_, double y_ |
Chromaticity blue primary point (e.g. x=0.15,
y=0.06) |
chroma-
GreenPrimary
|
double x & y |
double *x_, double *y_ |
double x_, double y_ |
Chromaticity green primary point (e.g. x=0.3,
y=0.6) |
chroma-
RedPrimary
|
double x & y |
double *x_, double *y_ |
double x_, double y_ |
Chromaticity red primary point (e.g. x=0.64,
y=0.33) |
chroma-
WhitePoint
|
double x & y |
double*x_, double *y_ |
double x_, double y_ |
Chromaticity white point (e.g. x=0.3127,
y=0.329) |
|
classType
|
ClassType |
void |
ClassType
class_ |
Image storage class. Note that
conversion from a DirectClass image to a PseudoClass image may result
in a loss of color due to the limited size of the palette (256 or
65535 colors). |
|
clipMask
|
Image |
void |
const Image &clipMask_ |
Associate a clip mask image with the current
image. The clip mask image must have the same dimensions as the current
image or an exception is thrown. Clipping occurs wherever pixels are
transparent in the clip mask image. Clipping Pass an invalid image to
unset an existing clip mask. |
|
colorFuzz
|
double |
void |
double fuzz_ |
Colors within this distance are considered
equal. A number of algorithms search for a target color. By
default the color must be exact. Use this option to match colors that
are close to the target color in RGB space. |
|
colorMap
|
Color |
unsigned int index_ |
unsigned int index_, const Color &color_ |
Color at colormap index. |
|
|
unsigned int
|
void
|
unsigned int entries_
|
Number of entries in the
colormap. Setting the colormap size may extend or truncate the colormap.
The maximum number of supported entries is specified by the MaxColormapSizeconstant,
and is dependent on the value of QuantumDepth when ImageMagick is
compiled. An exception is thrown if more entries are requested than may
be supported. Care should be taken when truncating the colormap to
ensure that the image colormap indexes reference valid colormap entries.
|
|
colorSpace
|
ColorspaceType
colorSpace_ |
void |
ColorspaceType
colorSpace_ |
The colorspace (e.g. CMYK) used to represent
the image pixel colors. Image pixels are always stored as RGB(A) except
for the case of CMY(K). |
|
columns
|
unsigned int |
void |
|
Image width |
|
comment
|
string |
void |
|
Image comment |
|
compose
|
CompositeOperator |
void |
CompositeOperator
compose_ |
Composition operator to be used when
composition is implicitly used (such as for image flattening). |
compress-
Type
|
CompressionType |
void |
CompressionType
compressType_ |
Image compresion type. The default is the
compression type of the specified image file. |
|
debug
|
bool |
void |
bool flag_ |
Enable printing of internal debug messages
from ImageMagick as it executes. |
defineValue
|
string
|
const std::string
&magick_, const std::string &key_
|
const std::string
&magick_, const std::string &key_, const std::string
&value_
|
Set or obtain a
definition string to applied when encoding or decoding the specified
format. The meanings of the definitions are format specific. The format
is designated by the magick_
argument, the format-specific key is designated by key_, and the associated value is
specified by value_. See the
defineSet() method if the key must be removed entirely.
|
defineSet
|
bool
|
const std::string
&magick_, const std::string &key_
|
const std::string
&magick_, const std::string &key_, bool flag_
|
Set or obtain a
definition flag to applied when encoding or decoding the specified
format.. Similar to the defineValue() method except that
passing the flag_ value 'true'
creates a value-less define with that format and key. Passing the flag_
value 'false' removes any existing matching definition. The method
returns 'true' if a matching key exists, and 'false' if no matching key
exists.
|
|
density
|
Geometry
(default 72x72) |
void |
const Geometry
&density_ |
Vertical and horizontal resolution in pixels
of the image. This option specifies an image density when decoding a
Postscript or Portable Document page. Often used with psPageSize. |
|
depth
|
unsigned int (8, 16, or 32) |
void |
unsigned int depth_ |
Image depth. Used to specify the bit depth
when reading or writing raw images or when the output format
supports multiple depths. Defaults to the quantum depth that
ImageMagick is compiled with. |
|
endian
|
EndianType |
void |
EndianType
endian_ |
Specify (or obtain) endian option for formats
which support it. |
|
directory
|
string |
void |
|
Tile names from within an image montage |
|
fileName
|
string |
void |
const string &fileName_ |
Image file name. |
|
fileSize
|
off_t |
void |
|
Number of bytes of the image on disk |
|
fillColor
|
Color |
void |
const Color &fillColor_ |
Color to use when filling drawn objects |
|
fillPattern
|
Image |
void |
const Image &fillPattern_ |
Pattern image to use when filling drawn
objects. |
|
fillRule
|
FillRule |
void |
const Magick::FillRule &fillRule_ |
Rule to use when filling drawn objects. |
|
filterType
|
FilterTypes |
void |
FilterTypes
filterType_ |
Filter to use when resizing image. The
reduction filter employed has a sigificant effect on the time required
to resize an image and the resulting quality. The default filter is Lanczos
which has been shown to produce high quality results when reducing most
images. |
|
font
|
string |
void |
const string &font_ |
Text rendering font. If the font is a fully
qualified X server font name, the font is obtained from an X
server. To use a TrueType font, precede the TrueType filename with an
@. Otherwise, specify a Postscript font name (e.g.
"helvetica"). |
|
fontPointsize
|
unsigned int |
void |
unsigned int pointSize_ |
Text rendering font point size |
|
fontTypeMetrics
|
TypeMetric |
const std::string &text_, TypeMetric *metrics |
|
Update metrics with font type metrics using
specified text, and current font and fontPointSize settings. |
|
format
|
string |
void |
|
Long form image format description. |
|
gamma
|
double (typical range 0.8 to 2.3) |
void |
|
Gamma level of the image. The same color
image displayed on two different workstations may
look different due to differences in the display monitor.
Use gamma correction to adjust for this
color difference. |
|
geometry
|
Geometry |
void |
|
Preferred size of the image when encoding. |
gifDispose-
Method
|
unsigned int
{ 0 = Disposal not specified,
1 = Do not dispose of graphic,
3 = Overwrite graphic with background color,
4 = Overwrite graphic with previous graphic. } |
void |
unsigned int disposeMethod_ |
GIF disposal method. This option is used to
control how successive frames are rendered (how the preceding frame is
disposed of) when creating a GIF animation. |
|
iccColorProfile
|
Blob |
void |
const Blob
&colorProfile_ |
ICC color profile. Supplied via a Blob since Magick++/ and ImageMagick do not
currently support formating this data structure directly.
Specifications are available from the
International Color Consortium for the format of ICC color profiles. |
interlace-
Type
|
InterlaceType |
void |
InterlaceType
interlace_ |
The type of interlacing scheme (default NoInterlace
). This option is used to specify the type of interlacing
scheme for raw image formats such as RGB or YUV. NoInterlace
means do not interlace, LineInterlace uses scanline
interlacing, and PlaneInterlace uses plane interlacing.
PartitionInterlace is like PlaneInterlace except the
different planes are saved to individual files (e.g.
image.R, image.G, and image.B). Use LineInterlace or
PlaneInterlace to create an interlaced GIF or progressive JPEG image. |
|
iptcProfile
|
Blob |
void |
const Blob &
iptcProfile_ |
IPTC profile. Supplied via a Blob since Magick++ and ImageMagick do not
currently support formating this data structure directly.
Specifications are available from the
International Press Telecommunications Council for IPTC profiles. |
|
label
|
string |
void |
const string &label_ |
Image label |
|
magick
|
string |
void |
const string &magick_ |
Get image format (e.g. "GIF") |
|
matte
|
bool |
void |
bool matteFlag_ |
True if the image has transparency. If set
True, store matte channel if the image has one otherwise create
an opaque one. |
|
matteColor
|
Color |
void |
const Color
&matteColor_ |
Image matte (frame) color |
meanError-
PerPixel
|
double |
void |
|
The mean error per pixel computed when an
image is color reduced. This parameter is only valid if verbose is set
to true and the image has just been quantized. |
modulusDepth
|
unsigned
int
|
void
|
unsigned
int depth_
|
Image
modulus depth (minimum number of bits required to support
red/green/blue components without loss of accuracy). The pixel modulus
depth may be decreased by supplying a value which is less than the
current value, updating the pixels (reducing accuracy) to the new depth.
The pixel modulus depth can not be increased over the current value
using this method.
|
|
monochrome
|
bool |
void |
bool flag_ |
Transform the image to black and white |
montage-
Geometry
|
Geometry |
void |
|
Tile size and offset within an image montage.
Only valid for montage images. |
normalized-
MaxError
|
double |
void |
|
The normalized max error per pixel computed
when an image is color reduced. This parameter is only valid if verbose
is set to true and the image has just been quantized. |
normalized-
MeanError
|
double |
void |
|
The normalized mean error per pixel computed
when an image is color reduced. This parameter is only valid if verbose
is set to true and the image has just been quantized. |
orientation
|
OrientationType |
void
|
OrientationType
orientation_ |
Image orientation.
Supported by some file formats such as DPX and TIFF. Useful for
turning the right way up.
|
|
packets
|
unsigned int |
void |
|
The number of runlength-encoded packets in
the image |
|
packetSize
|
unsigned int |
void |
|
The number of bytes in each pixel packet |
|
page
|
Geometry |
void |
const Geometry &pageSize_ |
Preferred size and location of an image
canvas.
Use this option to specify the dimensions
and position of the Postscript page in dots per inch or a TEXT page in
pixels. This option is typically used in concert with density .
Page may also be used to position a GIF
image (such as for a scene in an animation)
|
|
pixelColor
|
Color |
unsigned int x_, unsigned int y_ |
unsigned int x_, unsigned int y_, const Color &color_ |
Get/set pixel color at location x & y. |
|
|
Blob
|
const std::string name_
|
const std::string name_, const Blob
&colorProfile_
|
Get/set/remove a named
profile. Valid names include "*",
"8BIM", "ICM", "IPTC", or a user/format-defined profile name.
|
|
quality
|
unsigned int (0 to 100) |
void |
unsigned int quality_ |
JPEG/MIFF/PNG compression level (default 75). |
quantize-
Colors
|
unsigned int |
void |
unsigned int colors_ |
Preferred number of colors in the image. The
actual number of colors in the image may be less than your request, but
never more. Images with less unique colors than specified with this
option will have any duplicate or unused colors removed. |
quantize-
ColorSpace
|
ColorspaceType |
void |
ColorspaceType
colorSpace_ |
Colorspace to quantize colors in (default
RGB). Empirical evidence suggests that distances in color spaces such
as YUV or YIQ correspond to perceptual color differences more closely
than do distances in RGB space. These color spaces may give better
results when color reducing an image. |
quantize-
Dither
|
bool |
void |
bool flag_ |
Apply Floyd/Steinberg error diffusion to the
image. The basic strategy of dithering is to trade intensity
resolution for spatial resolution by
averaging the intensities of several
neighboring pixels. Images which suffer from
severe contouring when reducing colors can be
improved with this option. The quantizeColors or monochrome option must
be set for this option to take effect. |
quantize-
TreeDepth
|
unsigned int |
void |
unsigned int treeDepth_ |
Depth of the quantization color
classification tree. Values of 0 or 1 allow selection of the optimal
tree depth for the color reduction algorithm. Values between 2 and 8
may be used to manually adjust the tree depth. |
rendering-
Intent
|
RenderingIntent |
void |
RenderingIntent
render_ |
The type of rendering intent |
resolution-
Units
|
ResolutionType |
void |
ResolutionType
units_ |
Units of image resolution |
|
rows
|
unsigned int |
void |
|
The number of pixel rows in the image |
|
samplingFactor
|
string (e.g. "2x1,1x1,1x1") |
void |
const string &samplingFactor_ |
JPEG sampling factors |
|
scene
|
unsigned int |
void |
unsigned int scene_ |
Image scene number |
|
signature
|
string |
bool force_ = false |
|
Image MD5 signature. Set force_ to 'true' to
force re-computation of signature. |
|
size
|
Geometry |
void |
const Geometry
&geometry_ |
Width and height of a raw image (an image
which does not support width and height information). Size may
also be used to affect the image size read from a multi-resolution
format (e.g. Photo CD, JBIG, or JPEG. |
|
strokeAntiAlias
|
bool |
void |
bool flag_ |
Enable or disable anti-aliasing when drawing
object outlines. |
|
strokeColor
|
Color |
void |
const Color &strokeColor_ |
Color to use when drawing object outlines |
|
strokeDashOffset
|
unsigned int |
void |
double strokeDashOffset_ |
While drawing using a dash pattern, specify
distance into the dash pattern to start the dash (default 0). |
|
strokeDashArray
|
const double* |
void |
const double* strokeDashArray_ |
Specify the pattern of dashes and gaps used
to stroke paths. The strokeDashArray represents a zero-terminated
array of numbers that specify the lengths (in pixels) of alternating
dashes and gaps in user units. If an odd number of values is provided,
then the list of values is repeated to yield an even number of
values. A typical strokeDashArray_ array might contain the
members 5 3 2 0, where the zero value indicates the end of the pattern
array. |
|
strokeLineCap
|
LineCap |
void |
LineCap lineCap_ |
Specify the shape to be used at the corners
of paths (or other vector shapes) when they are stroked. Values of
LineJoin are UndefinedJoin, MiterJoin, RoundJoin, and BevelJoin. |
|
strokeLineJoin
|
LineJoin |
void |
LineJoin lineJoin_ |
Specify the shape to be used at the corners
of paths (or other vector shapes) when they are stroked. Values of
LineJoin are UndefinedJoin, MiterJoin, RoundJoin, and BevelJoin. |
|
strokeMiterLimit
|
unsigned int |
void |
unsigned int miterLimit_ |
Specify miter limit. When two line segments
meet at a sharp angle and miter joins have been specified for
'lineJoin', it is possible for the miter to extend far beyond the
thickness of the line stroking the path. The miterLimit' imposes a
limit on the ratio of the miter length to the 'lineWidth'. The default
value of this parameter is 4. |
|
strokeWidth
|
double |
void |
double strokeWidth_ |
Stroke width for use when drawing vector
objects (default one) |
|
strokePattern
|
Image |
void |
const Image &strokePattern_ |
Pattern image to use while drawing object
stroke (outlines). |
|
subImage
|
unsigned int |
void |
unsigned int subImage_ |
Subimage of an image sequence |
|
subRange
|
unsigned int |
void |
unsigned int subRange_ |
Number of images relative to the base image |
|
|
string
|
void
|
const std::string &encoding_
|
Specify the code set to use for text
annotations. The only character encoding which may be specified at
this time is "UTF-8" for representing Unicode as a
sequence of bytes. Specify an empty string to use the default ASCII
encoding. Successful text annotation using Unicode may require fonts
designed to support Unicode.
|
|
tileName
|
string |
void |
const string &tileName_ |
Tile name |
|
totalColors
|
unsigned long |
void |
|
Number of colors in the image |
|
type
|
ImageType |
void |
ImageType |
Image type. |
|
verbose
|
bool |
void |
bool verboseFlag_ |
Print detailed information about the image |
|
view
|
string |
void |
const string &view_ |
FlashPix viewing parameters. |
|
x11Display
|
string (e.g. "hostname:0.0") |
void |
const string &display_ |
X11 display to display to, obtain fonts from,
or to capture image from |
|
xResolution
|
double |
void |
|
x resolution of the image |
|
yResolution
|
double |
void |
|
y resolution of the image |
Low-Level Image Pixel Access
Image pixels (of type PixelPacket )
may be accessed directly via the Image Pixel Cache . The
image pixel cache is a rectangular window into the actual image pixels
(which may be in memory, memory-mapped from a disk file, or entirely on
disk). Two interfaces exist to access the Image Pixel Cache. The
interface described here (part of the Image class) supports only
one view at a time. See the Pixels
class for a more abstract interface which supports simultaneous pixel
views (up to the number of rows). As an analogy, the interface described
here relates to the Pixels class as
stdio's gets() relates to fgets(). The Pixels
class provides the more general form of the interface.
Obtain existing image pixels via getPixels(). Create a new
pixel region using setPixels().
In order to ensure that only the current generation of the image is
modified, the Image's modifyImage() method
should be invoked to reduce the reference count on the underlying image
to one. If this is not done, then it is possible for a previous
generation of the image to be modified due to the use of reference
counting when copying or constructing an Image.
Depending on the capabilities of the operating system, and the
relationship of the window to the image, the pixel cache may be a copy
of the pixels in the selected window, or it may be the actual image
pixels. In any case calling syncPixels() insures that the base
image is updated with the contents of the modified pixel cache. The
method readPixels() supports copying foreign pixel data formats
into the pixel cache according to the QuantumTypes. The method writePixels()
supports copying the pixels in the cache to a foreign pixel
representation according to the format specified by QuantumTypes.
The pixel region is effectively a small image in which the pixels
may be accessed, addressed, and updated, as shown in the following
example:
Image image("cow.png");
// Ensure that there are no other references to this image.
image.modifyImage();
// Set the image type to TrueColor
DirectClass representation.
image.type(TrueColorType);
// Request pixel region with size 60x40, and top origin at
20x30
int columns = 60;
PixelPacket *pixel_cache = image.getPixels(20,30,columns,40);
// Set pixel at column 5, and row 10 in the pixel cache to
red.
int column = 5;
int row = 10;
PixelPacket *pixel = pixel_cache+row*columns+column;
*pixel = Color("red");
// Save changes to underlying image .
image.syncPixels();
// Save updated image to file.
image.write("horse.png"); |
 |
The image cache supports the following methods:
Image Cache Methods
|
Method
|
Returns
|
Signature
|
Description
|
|
getConstPixels
|
const PixelPacket
* |
const int x_, const int y_, const unsigned
int columns_, const unsigned int rows_ |
Transfers pixels from the image to the pixel
cache as defined by the specified rectangular region. The returned pointer remains valid until the next getPixel,
getConstPixels, or setPixels call and should never be deallocated by the
user. |
|
getConstIndexes
|
const IndexPacket* |
void |
Returns a pointer to the Image pixel indexes
corresponding to a previous getPixel,
getConstPixels, or setPixels call. The
returned pointer remains valid until the next getPixel, getConstPixels,
or setPixels call and should never be deallocated by the user. Only valid for PseudoClass images or CMYKA images. The
pixel indexes represent an array of type IndexPacket, with each entry
corresponding to an x,y pixel position. For PseudoClass images, the
entry's value is the offset into the colormap (see colorMap
) for that pixel. For CMYKA images, the indexes are used to contain the
alpha channel. |
|
getIndexes
|
IndexPacket* |
void |
Returns a pointer to the Image pixel indexes
corresponding to the pixel region requested by the last getConstPixels , getPixels
, or setPixels call. The
returned pointer remains valid until the next getPixel, getConstPixels,
or setPixels call and should never be deallocated by the user. Only valid for PseudoClass images or
CMYKA images. The pixel indexes represent an array of type
IndexPacket, with each entry corresponding to a pixel x,y position. For
PseudoClass images, the entry's value is the offset into the colormap
(see colorMap ) for that pixel. For CMYKA
images, the indexes are used to contain the alpha channel. |
|
getPixels
|
PixelPacket * |
const int x_, const int y_, const unsigned
int columns_, const unsigned int rows_ |
Transfers pixels from the image to the pixel
cache as defined by the specified rectangular region. Modified pixels
may be subsequently transferred back to the image via syncPixels. The returned pointer remains valid until the next getPixel,
getConstPixels, or setPixels call and should never be deallocated by the
user. |
|
setPixels
|
PixelPacket * |
const int x_, const int y_, const unsigned
int columns_, const unsigned int rows_ |
Allocates a pixel cache region to store image
pixels as defined by the region rectangle. This area is
subsequently transferred from the pixel cache to the image via
syncPixels. The returned pointer remains
valid until the next getPixel, getConstPixels, or setPixels call and
should never be deallocated by the user. |
|
syncPixels
|
void |
void |
Transfers the image cache pixels to the image. |
|
readPixels
|
void |
QuantumTypes
quantum_, unsigned char *source_, |
Transfers one or more pixel components from a
buffer or file into the image pixel cache of an image. ReadPixels is
typically used to support image decoders. The region transferred
corresponds to the region set by a preceding setPixels call. |
|
writePixels
|
void |
QuantumTypes
quantum_, unsigned char *destination_ |
Transfers one or more pixel components from
the image pixel cache to a buffer or file. WritePixels is typically
used to support image encoders. The region transferred corresponds to
the region set by a preceding getPixels or getConstPixels call. |
|