Drawable provides a convenient interface for preparing vector, image, or text arguments for the Image::draw() method. Each instance of a Drawable sub-class represents a single drawable object. Drawable objects may be drawn "one-by-one" via multiple invocations of the Image draw() method, or may be drawn "all-at-once" by passing a list of Drawable objects to the Image draw() method. The one-by-one approach is convenient for simple drawings, while the list-based approach is appropriate for drawings which require more sophistication.
The following is an example using the Drawable subclasses with a one-by-one approach to draw the following figure:
Since Drawable is an object it may be saved in an array or a list for later (perhaps repeated) use. The following example shows how to draw the same figure using the list-based approach
int main(int /*argc*/,char **/*argv*/) { try { // Create base image (white image of 300 by 200 pixels) Image image( Geometry(300,200), Color("white") );
// Construct drawing list std::list<Magick::Drawable> drawList;
// Add some drawing options to drawing list drawList.push_back(DrawableStrokeColor("red")); // Outline color drawList.push_back(DrawableStrokeWidth(5)); // Stroke width drawList.push_back(DrawableFillColor("green")); // Fill color
// Add a Circle to drawing list drawList.push_back(DrawableCircle(100,100, 50,100));
// Add a Rectangle to drawing list drawList.push_back(DrawableRectangle(200,100, 270,170));
// Draw everything using completed drawing list image.draw(drawList);
Drawable depends on the simple Coordinate structure which represents a pair of x,y coodinates. The methods provided by the Coordinate structure are shown in the following table:
Coordinate Structure Methods
Method/Member
Signature
Description
Coordinate
void
Default Constructor
double x_, double y_
Constructor, setting first & second
x
double x_
x coordinate member
y
double y_
y coordinate member
The Drawable classes are shown in the following table. Only constructor signatures are documented here. Each Drawable class also provides methods by which each individual parameter may be adjusted.
Specify a transformation matrix to adjust scaling, rotation, and translation (coordinate transformation) for subsequently drawn objects in the same or decendent drawing context. The sx_ & sy_ parameters represent the x & y scale factors, the rx_ & ry_ parameters represent the x & y rotation, and the tx_ & ty_ parameters represent the x & y translation.
void
Specify a transformation matrix to adjust scaling, rotation, and translation (coordinate transformation) for subsequently drawn objects in the same or decendent drawing context. Initialized to unity (no effect) affine values. Use class methods (not currently documented) to adjust individual parameters from their unity values.
Draw an arc using the stroke color and based on the circle starting at coordinates startX_,startY_, and ending with coordinates endX_,endY_, and bounded by the rotational arc startDegrees_,endDegrees_
DrawableBezier
const std::list<Magick::Coordinate> &coordinates_
Draw a bezier curve using the stroke color and based on the coordinates specified by the coordinates_ list.
Draw a circle using the stroke color and thickness using specified origin and perimeter coordinates. If a fill color is specified, then the object is filled.
Color image according to paintMethod. The point method recolors the target pixel. The replace method recolors any pixel that matches the color of the target pixel. Floodfill recolors any pixel that matches the color of the target pixel and is a neighbor, whereas filltoborder recolors any neighbor pixel that is not the border color. Finally, reset recolors all pixels.
Composite current image with contents of specified image, at specified coordinates. If the matte attribute is set to true, then the image composition will consider an alpha channel, or transparency, present in the image file so that non-opaque portions allow part (or all) of the composite image to show through.
Composite current image with contents of specified image, rendered with specified width and height, at specified coordinates. If the matte attribute is set to true, then the image composition will consider an alpha channel, or transparency, present in the image file so that non-opaque portions allow part (or all) of the composite image to show through. If the specified width or height is zero, then the image is composited at its natural size, without enlargement or reduction.
Composite current image with contents of specified image, rendered with specified width and height, using specified composition algorithm, at specified coordinates. If the matte attribute is set to true, then the image composition will consider an alpha channel, or transparency, present in the image file so that non-opaque portions allow part (or all) of the composite image to show through. If the specified width or height is zero, then the image is composited at its natural size, without enlargement or reduction.
Specify the pattern of dashes and gaps used to stroke paths. The strokeDashArray represents a zero-terminated array of numbers that specify the lengths of alternating dashes and gaps in pixels. 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.
DrawableDashOffset
double offset_
Specify the distance into the dash pattern to start the dash. See documentation on SVG's stroke-dashoffset property for usage details.
Draw an ellipse using the stroke color and thickness, specified origin, x & y radius, as well as specified start and end of arc in degrees. If a fill color is specified, then the object is filled.
Specify the algorithm which is to be used to determine what parts of the canvas are included inside the shape. See documentation on SVG's fill-rule property for usage details.
DrawableFillOpacity
double opacity_
Specify opacity to use when drawing using fill color.
DrawableFont
const std::string &font_
Specify font name to use when drawing text.
const std::string &family_, StyleType style_,
unsigned long weight_, StretchType stretch_
Specify font family, style, weight (one of the set { 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900 } with 400 being the normal size), and stretch to be used to select the font used when drawing text. Wildcard matches may be applied to style via the AnyStyle enumeration, applied to weight if weight is zero, and applied to stretch via the AnyStretch enumeration.
Change the pixel matte value to transparent. The point method changes the matte value of the target pixel. The replace method changes the matte value of any pixel that matches the color of the target pixel. Floodfill changes the matte value of any pixel that matches the color of the target pixel and is a neighbor, whereas filltoborder changes the matte value of any neighbor pixel that is not the border color, Finally reset changes the matte value of all pixels.
DrawableMiterLimit
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.
DrawablePath
const std::list<Magick::VPath> &path_
Draw on image using vector path.
DrawablePoint
double x_, double y_
Draw a point using stroke color and thickness at coordinate
DrawablePointSize
double pointSize_
Set font point size.
DrawablePolygon
const std::list<Magick::Coordinate> &coordinates_
Draw an arbitrary polygon using stroke color and thickness consisting of three or more coordinates contained in an STL list. If a fill color is specified, then the object is filled.
DrawablePolyline
const std::list<Magick::Coordinate> &coordinates_
Draw an arbitrary polyline using stroke color and thickness consisting of three or more coordinates contained in an STL list. If a fill color is specified, then the object is filled.
DrawablePopClipPath
void
Pop (terminate) clip path definition started by DrawablePushClipPath.
DrawablePopGraphicContext
void
Pop Graphic Context. Removing the current graphic context from the graphic context stack restores the options to the values they had prior to the preceding DrawablePushGraphicContext operation.
DrawablePushClipPath
const std::string &id_
Push (create) clip path definition with id_. Clip patch definition consists of subsequent drawing commands, terminated by DrawablePopClipPath.
DrawablePushGraphicContext
void
Push Graphic Context. When a graphic context is pushed, options set after the context is pushed (such as coordinate transformations, color settings, etc.) are saved to a new graphic context. This allows related options to be saved on a graphic context "stack" in order to support heirarchical nesting of options. When DrawablePopGraphicContext is used to pop the current graphic context, the options in effect during the last DrawablePushGraphicContext operation are restored.
DrawablePushPattern
std::string &id_, long x_, long y_, long width_, long height_
Start a pattern definition with arbitrary pattern name specified by id_, pattern offset specified by x_ and y_, and pattern size specified by width_ and height_. The pattern is defined within the coordinate system defined by the specified offset and size. Arbitrary drawing objects (including DrawableCompositeImage) may be specified between DrawablePushPattern and DrawablePopPattern in order to draw the pattern. Normally the pair DrawablePushGraphicContext & DrawablePopGraphicContext are used to enclose a pattern definition. Pattern definitions are terminated by a DrawablePopPattern object.
Draw a rectangle using stroke color and thickness from upper-left coordinates to lower-right coordinates. If a fill color is specified, then the object is filled.
DrawableRotation
double angle_
Set rotation to use when drawing (coordinate transformation).
Draw a rounded rectangle using stroke color and thickness, with specified center coordinate, specified width and height, and specified corner width and height. If a fill color is specified, then the object is filled.
DrawableScaling
double x_, double y_
Apply scaling in x and y direction while drawing objects (coordinate transformation).
DrawableSkewX
double angle_
Apply Skew in X direction (coordinate transformation)
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.
DrawableStrokeOpacity
double opacity_
Opacity to use when drawing lines or object outlines.
DrawableStrokeWidth
double width_
Set width to use when drawing lines or object outlines.
DrawableText
double x_, double y_, std::string text_
Annotate image with text using stroke color, font, font pointsize, and box color (text background color), at specified coordinates. If text contains special format characters the image filename, type, width, height, or other image attributes may be incorporated in the text (see label()).
Annotate image with text represented with text encoding, using current stroke color, font, font pointsize, and box color (text background color), at specified coordinates. If text contains special format characters the image filename, type, width, height, or other image attributes may be incorporated in the text (see label()).
The text encoding specifies 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 set text encoding to the system's default. Successful text annotation using Unicode may require fonts designed to support Unicode.
DrawableTextAntialias
bool flag_
Antialias while drawing text (default true). The main reason to disable text antialiasing is to avoid adding new colors to the image.
Specify decoration (e.g. UnderlineDecoration) to apply to text.
DrawableTextUnderColor
const Color &color_
Draw a box under rendered text using the specified color.
DrawableTranslation
double x_, double y_
Apply coordinate translation (set new coordinate origin).
DrawableViewbox
unsigned long x1_, unsigned long y1_, unsigned long x2_, unsigned long y2_
Dimensions of the output viewbox. If the image is to be written to a vector format (e.g. MVG or SVG), then a DrawablePushGraphicContext() object should be pushed to the head of the list, followed by a DrawableViewbox() statement to establish the output canvas size. A matching DrawablePopGraphicContext() object should be pushed to the tail of the list.
Vector Path Classes
The vector paths supported by Magick++ are based on those supported by the SVG XML specification. Vector paths are not directly drawable, they must first be supplied as a constructor argument to the DrawablePath class in order to create a drawable object. The DrawablePath class effectively creates a drawable compound component which may be replayed as desired. If the drawable compound component consists only of vector path objects using relative coordinates then the object may be positioned on the image by preceding it with a DrawablePath which sets the current drawing coordinate. Alternatively coordinate transforms may be used to translate the origin in order to position the object, rotate it, skew it, or scale it.
The "moveto" commands
The "moveto" commands establish a new current point. The effect is as if the "pen" were lifted and moved to a new location. A path data segment must begin with either one of the "moveto" commands or one of the "arc" commands. Subsequent "moveto" commands (i.e., when the "moveto" is not the first command) represent the start of a new subpath:
Moveto Classes
Sub-Class
Constructor Signature
Description
PathMovetoAbs
const Magick::Coordinate &coordinate_
Start a new sub-path at the given coordinate. PathMovetoAbs indicates that absolute coordinates will follow; PathMovetoRel indicates that relative coordinates will follow. If a relative moveto appears as the first element of the path, then it is treated as a pair of absolute coordinates. If a moveto is followed by multiple pairs of coordinates, the subsequent pairs are treated as implicit lineto commands.
const std::list<Magick::Coordinate> &coordinates_
PathMovetoRel
const Magick::Coordinate &coordinate_
const std::list<Magick::Coordinate> &coordinates_
The "closepath" command
The "closepath" command causes an automatic straight line to be drawn from the current point to the initial point of the current subpath:
Closepath Classes
Sub-Class
Constructor Signature
Description
PathClosePath
void
Close the current subpath by drawing a straight line from the current point to current subpath's most recent starting point (usually, the most recent moveto point).
The "lineto" commands
The various "lineto" commands draw straight lines from the current point to a new point:
Lineto Classes
Sub-Class
Constructor Signature
Description
PathLinetoAbs
const Magick::Coordinate& coordinate_
Draw a line from the current point to the given coordinate which becomes the new current point. PathLinetoAbs indicates that absolute coordinates are used; PathLinetoRel indicates that relative coordinates are used. A number of coordinates pairs may be specified in a list to draw a polyline. At the end of the command, the new current point is set to the final set of coordinates provided.
const std::list<Magick::Coordinate> &coordinates_
PathLinetoRel
const Magick::Coordinate& coordinate_
const std::list<Magick::Coordinate> &coordinates_
PathLinetoHorizontalAbs
double x_
Draws a horizontal line from the current point (cpx, cpy) to (x, cpy). PathLinetoHorizontalAbs indicates that absolute coordinates are supplied; PathLinetoHorizontalRel indicates that relative coordinates are supplied. At the end of the command, the new current point becomes (x, cpy) for the final value of x.
PathLinetoHorizontalRel
double x_
PathLinetoVerticalAbs
double y_
Draws a vertical line from the current point (cpx, cpy) to (cpx, y). PathLinetoVerticalAbs indicates that absolute coordinates are supplied; PathLinetoVerticalRel indicates that relative coordinates are supplied. At the end of the command, the new current point becomes (cpx, y) for the final value of y.
PathLinetoVerticalRel
double y_
The curve commands
These three groups of commands draw curves:
Cubic Bézier commands. A cubic Bézier segment is defined by a start point, an end point, and two control points.
Quadratic Bézier commands. A quadratic Bézier segment is defined by a start point, an end point, and one control point.
Draws a cubic Bézier curve from the current point to (x,y) using (x1,y1) as the control point at the beginning of the curve and (x2,y2) as the control point at the end of the curve. PathCurvetoAbs indicates that absolutecoordinates will follow; PathCurvetoRel indicates that relative coordinates will follow. Multiple sets of coordinates may be specified to draw a polybezier. At the end of the command, the new current point becomes the final (x,y) coordinate pair used in the polybezier.
const std::list<Magick::PathCurvetoArgs> &args_
PathCurvetoRel
const Magick::PathCurvetoArgs &args_
const std::list<Magick::PathCurvetoArgs> &args_
PathSmoothCurvetoAbs
const Magick::Coordinate &coordinates_
Draws a cubic Bézier curve from the current point to (x,y). The first control point is assumed to be the reflection of the second control point on the previous command relative to the current point. (If there is no previous command or if the previous command was not an PathCurvetoAbs, PathCurvetoRel, PathSmoothCurvetoAbs or PathSmoothCurvetoRel, assume the first control point is coincident with the current point.) (x2,y2) is the second control point (i.e., the control point at the end of the curve). PathSmoothCurvetoAbs indicates that absolute coordinates will follow; PathSmoothCurvetoRel indicates that relative coordinates will follow. Multiple sets of coordinates may be specified to draw a polybezier. At the end of the command, the new current point becomes the final (x,y) coordinate pair used in the polybezier.
const std::list<Magick::Coordinate> &coordinates_
PathSmoothCurvetoRel
const Magick::Coordinate &coordinates_
const std::list<Magick::Coordinate> &coordinates_
The quadratic Bézier curve commands
The quadratic Bézier commands depend on the PathQuadraticCurvetoArgs argument class, which has the constructor signature:
Draws a quadratic Bézier curve from the current point to (x,y) using (x1,y1) as the control point. PathQuadraticCurvetoAbs indicates that absolute coordinates will follow; PathQuadraticCurvetoRel indicates that relative coordinates will follow. Multiple sets of coordinates may be specified to draw a polybezier. At the end of the command, the new current point becomes the final (x,y) coordinate pair used in the polybezier.
Draws a quadratic Bézier curve from the current point to (x,y). The control point is assumed to be the reflection of the control point on the previous
command relative to the current point. (If there is no previous command or if the previous command was not a PathQuadraticCurvetoAbs, PathQuadraticCurvetoRel, PathSmoothQuadraticCurvetoAbs or PathSmoothQuadraticCurvetoRel, assume the control point is coincident with the current point.) PathSmoothQuadraticCurvetoAbs indicates that absolute coordinates will follow; PathSmoothQuadraticCurvetoRel indicates that relative coordinates will follow. At the end of the command, the new current point becomes the final (x,y) coordinate pair used in the polybezier.
const std::list<Magick::Coordinate> &coordinates_
PathSmoothQuadraticCurvetoRel
const Magick::Coordinate &coordinate_
const std::list<Magick::Coordinate> &coordinates_
The elliptical arc curve commands
The elliptical arc curve commands depend on the PathArcArgs argument class, which has the constructor signature:
Draws an elliptical arc from the current point to (x, y). The size and orientation of the ellipse are defined by two radii (radiusX, radiusY) and an xAxisRotation, which indicates how the ellipse as a whole is rotated relative to the current coordinate system. The center (cx, cy) of the ellipse is calculated automatically to satisfy the constraints imposed by the other parameters. largeArcFlag and sweepFlag contribute to the automatic calculations and help determine how the arc is drawn. If largeArcFlag is true then draw the larger of the available arcs. If sweepFlag is true, then draw the arc matching a clock-wise rotation.
