An interface for recording graphical operations.

Canvas objects are used in creating Picture objects, which can themselves be used with a SceneBuilder to build a Scene. In normal usage, however, this is all handled by the framework.

A canvas has a current transformation matrix which is applied to all operations. Initially, the transformation matrix is the identity transform. It can be modified using the translate, scale, rotate, skew, transform, and setMatrix methods.

A canvas also has a current clip region which is applied to all operations. Initially, the clip region is infinite. It can be modified using the clipRect, clipRRect, and clipPath methods.

The current transform and clip can be saved and restored using the stack managed by the save, saveLayer, and restore methods.

Constructors

Canvas(PictureRecorder recorder, Rect cullRect)

Creates a canvas for recording graphical operations into the given picture recorder.

Properties

hashCode → int

Get a hash code for this object.

read-only, inherited
runtimeType → Type

A representation of the runtime type of the object.

read-only, inherited

Operators

operator ==(other) → bool

The equality operator.

inherited

Methods

clipPath(Path path) → void

Reduces the clip region to the intersection of the current clip and the given Path.

clipRect(Rect rect) → void

Reduces the clip region to the intersection of the current clip and the given rectangle.

clipRRect(RRect rrect) → void

Reduces the clip region to the intersection of the current clip and the given rounded rectangle.

drawArc(Rect rect, double startAngle, double sweepAngle, bool useCenter, Paint paint) → void

Draw an arc scaled to fit inside the given rectangle. It starts from startAngle radians around the oval up to startAngle + sweepAngle radians around the oval, with zero radians being the point on the right hand side of the oval that crosses the horizontal line that intersects the center of the rectangle and with positive angles going clockwise around the oval. If useCenter is true, the arc is closed back to the center, forming a circle sector. Otherwise, the arc is not closed, forming a circle segment.

drawAtlas(Image atlas, List<RSTransform> transforms, List<Rect> rects, List<Color> colors, TransferMode transferMode, Rect cullRect, Paint paint) → void

drawCircle(Point c, double radius, Paint paint) → void

Draws a circle centered at the point given by the first two arguments and that has the radius given by the third argument, with the Paint given in the fourth argument. Whether the circle is filled or stroked (or both) is controlled by Paint.style.

drawColor(Color color, TransferMode transferMode) → void

Paints the given Color onto the canvas, applying the given TransferMode, with the given color being the source and the background being the destination.

drawDRRect(RRect outer, RRect inner, Paint paint) → void

Draws a shape consisting of the difference between two rounded rectangles with the given Paint. Whether this shape is filled or stroked (or both) is controlled by Paint.style.

drawImage(Image image, Point p, Paint paint) → void

Draws the given Image into the canvas with its top-left corner at the given Point. The image is composited into the canvas using the given Paint.

drawImageNine(Image image, Rect center, Rect dst, Paint paint) → void

Draws the given Image into the canvas using the given Paint.

drawImageRect(Image image, Rect src, Rect dst, Paint paint) → void

Draws the subset of the given image described by the src argument into the canvas in the axis-aligned rectangle given by the dst argument.

drawLine(Point p1, Point p2, Paint paint) → void

Draws a line between the given Points using the given paint. The line is stroked, the value of the Paint.style is ignored for this call.

drawOval(Rect rect, Paint paint) → void

Draws an axis-aligned oval that fills the given axis-aligned rectangle with the given Paint. Whether the oval is filled or stroked (or both) is controlled by Paint.style.

drawPaint(Paint paint) → void

Fills the canvas with the given Paint.

drawParagraph(Paragraph paragraph, Offset offset) → void

Draws the text in the given paragraph into this canvas at the given offset.

drawPath(Path path, Paint paint) → void

Draws the given Path with the given Paint. Whether this shape is filled or stroked (or both) is controlled by Paint.style. If the path is filled, then subpaths within it are implicitly closed (see Path.close).

drawPicture(Picture picture) → void

Draw the given picture onto the canvas. To create a picture, see PictureRecorder.

drawPoints(PointMode pointMode, List<Point> points, Paint paint) → void

Draws a sequence of points according to the given PointMode.

drawRect(Rect rect, Paint paint) → void

Draws a rectangle with the given Paint. Whether the rectangle is filled or stroked (or both) is controlled by Paint.style.

drawRRect(RRect rrect, Paint paint) → void

Draws a rounded rectangle with the given Paint. Whether the rectangle is filled or stroked (or both) is controlled by Paint.style.

drawVertices(VertexMode vertexMode, List<Point> vertices, List<Point> textureCoordinates, List<Color> colors, TransferMode transferMode, List<int> indicies, Paint paint) → void

getSaveCount() → int

Returns the number of items on the save stack, including the initial state. This means it returns 1 for a clean canvas, and that each call to save and saveLayer increments it, and that each matching call to restore decrements it.

restore() → void

Pops the current save stack, if there is anything to pop. Otherwise, does nothing.

rotate(double radians) → void

Add a rotation to the current transform. The argument is in radians clockwise.

save() → void

Saves a copy of the current transform and clip on the save stack.

saveLayer(Rect bounds, Paint paint) → void

Saves a copy of the current transform and clip on the save stack, and then creates a new group which subsequent calls will become a part of. When the save stack is later popped, the group will be flattened into a layer and have the given paint's Paint.colorFilter and Paint.transferMode applied.

scale(double sx, double sy) → void

Add an axis-aligned scale to the current transform, scaling by the first argument in the horizontal direction and the second in the vertical direction.

setMatrix(Float64List matrix4) → void

Replaces the current transform with the specified 4⨉4 transformation matrix specified as a list of values in column-major order.

skew(double sx, double sy) → void

Add an axis-aligned skew to the current transform, with the first argument being the horizontal skew in radians clockwise around the origin, and the second argument being the vertical skew in radians clockwise around the origin.

transform(Float64List matrix4) → void

Multiply the current transform by the specified 4⨉4 transformation matrix specified as a list of values in column-major order.

translate(double dx, double dy) → void

Add a translation to the current transform, shifting the coordinate space horizontally by the first argument and vertically by the second argument.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a non-existent method or property is accessed.

inherited
toString() → String

Returns a string representation of this object.

inherited