Categorygithub.com/tdewolff/canvas
modulepackage
0.0.0-20250209140343-015076d8ff76
Repository: https://github.com/tdewolff/canvas.git
Documentation: pkg.go.dev
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# README

Canvas

API reference User guide Go Report Card Coverage Status

API documentation

User guide

Live HTMLCanvas demo

Canvas is a common vector drawing target that can output SVG, PDF, EPS, raster images (PNG, JPG, GIF, ...), HTML Canvas through WASM, OpenGL, and Gio. It has a wide range of path manipulation functionality such as flattening, stroking and dashing implemented. Additionally, it has a text formatter and embeds and subsets fonts (TTF, OTF, WOFF, WOFF2, or EOT) or converts them to outlines. It can be considered a Cairo or node-canvas alternative in Go. See the example below in Figure 1 for an overview of the functionality.

Preview

Figure 1: top-left you can see text being fitted into a box, justified using Donald Knuth's linea breaking algorithm to stretch the spaces between words to fill the whole width. You can observe a variety of styles and text decorations applied, as well as support for LTR/RTL mixing and complex scripts. In the bottom-right the word "stroke" is being stroked and drawn as a path. Top-right we see a LaTeX formula that has been converted to a path. Left of that we see an ellipse showcasing precise dashing, notably the length of e.g. the short dash is equal wherever it is on the curve. Note that the dashes themselves are elliptical arcs as well (thus exactly precise even if magnified greatly). To the right we see a closed polygon of four points being smoothed by cubic Béziers that are smooth along the whole path, and the blue line on the left shows a smoothed open path. On the bottom you can see a rotated rasterized image. The bottom-left shows path boolean operations. The result is equivalent for all renderers (PNG, PDF, SVG, etc.).

Sponsors

I'm actively looking for support in the form of donations or sponsorships to keep developing this library and highly appreciate any gesture. Please see the Sponsors button in GitHub for ways to contribute, or contact me directly.

State

Whether this library is ready for production environments is up to your own judgment. In general, this library is written thoughtfully and complete, but the scope of this work is so big and the implementation can be quite complex that inevitably it must have a great amount of bugs. Effort was put in writing unit and fuzz tests so that I suspect only special use-cases will stumble into bugs, but coverage is still lacking. As time permits, work is done to flesh-out functionality, find bugs, and optimize code. Optimization could be in execution time / reducing code complexity, reducing memory footprint, or reducing the length of paths from operation.

Execution performance is actually really good, especially the rasterizer is highly optimized with ASM. See for example a comparison of an extreme case in https://github.com/tdewolff/canvas/issues/280#issuecomment-1995990038, where this library is at least twice as fast as existing solutions, and can handle bigger images than the likes of Inkscape and Cairo.

The path intersection code and path boolean operation code is quite complete and fast, and more importantly has a time complexity of O(n log n). It is numerically stable and does not suffer from floating-point precision errors.

Please issue bug reports or feature requests to help this library mature! All help is appreciated. Also see Wiki - Planning for an inexhaustive list of ideas and TODOs.

Features

General

  • Path segment types: MoveTo, LineTo, QuadTo, CubeTo, ArcTo, Close (see Paths)
  • Precise path flattening, stroking, and dashing for all segment types (see papers below)
  • Smooth spline generation through points for open and closed paths
  • LaTeX to path conversion (native Go and CGO implementations available)
  • sRGB compliance (use SRGBColorSpace, only available for rasterizer)

Rendering targets

Paths can be exported as or rendered to:

  • Raster images (PNG, GIF, JPEG, TIFF, BMP, WEBP, AVIF, ...)
  • PDF
  • SVG and SVGZ
  • PS and EPS
  • HTMLCanvas
  • OpenGL
  • Gio
  • Fyne

Additionally, it has bindings to be used as renderer for:

See Renderers for more information.

Stable path boolean operations

Numerically stable (!) path boolean operations, supporting AND, OR, XOR, NOT, and DIV operations in O((n+k) log n), with n the number of segments and k the number of intersections. This is very fast and allows handling huge paths. It uses 64-bit floating-point precision for highly accurate computation and employs an additional strategy to ensure numerical stability. In particular:

  • Allows paths, subject or clipping, with any number of (overlapping) contours.
  • Allows contours with any orientation, clockwise or anticlockwise.
  • Contours may be concave or of any shape.
  • Contours may self-intersect any number of times.
  • Segments may overlap any number of times by any contour.
  • Points may be crossed any number of times.
  • Segments may be vertical.
  • Clipping path is implicitly closed (it makes no sense if it's an open path).
  • Subject path may be either open or closed.
  • Paths are currently flattened, but supporting Bézier or elliptical arcs is a WIP (not anytime soon).

Numerical stability refers to cases where two segments are extremely close where floating-point precision can alter the computation whether they intersect or not. This is a very difficult problem to solve, and many libraries cannot handle this properly (nor can they handle 'degenerate' paths in general, see the list of properties above). Note that fixed-point precision suffers from the same problem. This library builds on papers from Bentley & Ottmann, de Berg, Martínez, Hobby, and Hershberger (see bibliography below).

Correctness and performance has been tested by drawing all land masses and islands from OpenStreetMap at various scales, which is a huge input (1 GB of compressed Shape files) with extremely degenerate data (many overlapping segments, overlapping points, vertical segments, self-intersections, extremely close intersections, different contour orientations, and so on).

TODO: add benchmark with other libraries

See Boolean operations for more information.

Advanced text rendering

High-quality (comparable to TeX) text rendering and line breaking. It uses HarfBuzz for text shaping (native Go and CGO implementations available) and FriBidi for text bidirectionality (native Go and CGO implementations available), and uses Donald Knuth's line breaking algorithm for text layout. This enables the following features:

  • Align text left, center, right and justified, including indentation.
  • Align text top, middle, bottom in a text box, including setting line spacing.
  • Handle any script, eg. latin, cyrillic, devanagari, arabic, hebrew, han, etc.
  • Handle left-to-right, right-to-left, or top-to-bottom/bottom-to-top writing systems.
  • Mix scripts and fonts in a single line, eg. combine latin and arabic, or bold and regular styles.

Additionally, many font formats are supported (such as TTF, OTF, WOFF, WOFF2, EOT) and rendering can apply a gamma correction of 1.43 for better results. See Fonts & Text for more information.

Examples

Amsterdam city centre: the centre of Amsterdam is drawn from data loaded from the Open Street Map API.

Mauna-Loa CO2 concentration: using data from the Mauna-Loa observatory, carbon dioxide concentrations over time are drawn

Text document: an example of a text document using the PDF backend.

OpenGL: an example using the OpenGL backend.

Gio: an example using the Gio backend.

Fyne: an example using the Fyne backend.

TeX/PGF: an example showing the usage of the PGF (TikZ) LaTeX package as renderer in order to generated a PDF using LaTeX.

go-chart: an example using the go-chart library, plotting a financial graph.

gonum/plot: an example using the gonum/plot library.

HTMLCanvas: an example using the HTMLCanvas backend, see the live demo.

Users

This is a non-exhaustive list of library users I've come across. PRs are welcome to extend the list!

Articles

My own

Papers

License

Released under the MIT license.

Be aware that Fribidi uses the LGPL license.

# Packages

# Functions

Arc returns a circular arc with radius r and theta0 and theta1 the angles in degrees of the ellipse (before rot is applies) between which the arc will run.
BeveledRectangle returns a rectangle of width w and height h with beveled corners at distance r from the corner.
CacheSystemFonts will write and load the list of system fonts to the given filename.
Circle returns a circle of radius r.
DPI (dots-per-inch) for the resolution of rasterization.
DPMM (dots-per-millimeter) for the resolution of rasterization.
DrawPreview draws the canvas's preview to a Context.
DrawPreviewWithAssets draws the canvas's preview to a Context with assets preloaded.
DVI2Path parses a DVI file (output from TeX) and returns a path.
Ellipse returns an ellipse of radii rx and ry.
EllipsePos returns the position on the ellipse at angle theta.
EllipticalArc returns an elliptical arc with radii rx and ry, with rot the counter clockwise rotation in degrees, and theta0 and theta1 the angles in degrees of the ellipse (before rot is applies) between which the arc will run.
Equal returns true if a and b are equal within an absolute tolerance of Epsilon or within a relative tolerance of Epsilon (relative to the largest of the two).
FindLocalFont finds the path to a font from the system's fonts.
FindSystemFont finds the path to a font from the system's fonts.
Grid returns a stroked grid of width w and height h, with grid line thickness r, and the number of cells horizontally and vertically as nx and ny respectively.
Hex parses a CSS hexadecimal color such as e.g.
Interval returns true if f is in closed interval [lower-Epsilon,upper+Epsilon] where lower and upper can be interchanged.
IntervalExclusive returns true if f is in open interval [lower+Epsilon,upper-Epsilon] where lower and upper can be interchanged.
Line returns a line segment of from (0,0) to (x,y).
LoadFont loads a font from memory.
LoadFontCollection loads a font from a collection file and uses the font at the specified index.
LoadFontFile loads a font from a file.
LoadLocalFont loads a font from the system's fonts.
LoadSystemFont loads a font from the system's fonts.
MustParseSVGPath parses an SVG path data string and panics if it fails.
New returns a new canvas with width and height in millimeters, that records all drawing operations into layers.
NewContext returns a new context which is a wrapper around a renderer.
NewCrossHatch returns a new cross hatch pattern of two regular line hatches at different angles and with different distance intervals.
NewFontFamily returns a new font family.
NewFontSubsetter returns a new font subsetter.
NewFromSize returns a new canvas of given size in millimeters, that records all drawing operations into layers.
NewHatchPattern returns a new hatch pattern.
NewJPEGImage parses a JPEG image.
NewLinearGradient returns a new linear gradient pattern.
NewLineHatch returns a new line hatch pattern with lines at an angle with a spacing of distance.
NewPathFromData returns a new path using the raw data.
NewPNGImage parses a PNG image.
NewRadialGradient returns a new radial gradient pattern.
NewRichText returns a new rich text with the given default font face.
NewShapeHatch returns a new shape hatch that repeats the given shape over a rhombus primitive cell with sides of length distance.
NewTextBox is an advanced text formatter that will format text placement based on the settings.
NewTextLine is a simple text line using a single font face, a string (supporting new lines) and horizontal alignment (Left, Center, Right).
ParallelogramCell is a paralellogram cell with sides of length a and b at an angle of rot degrees used for tiling.
ParseLaTeX parse a LaTeX formula (that what is between $...$) and returns a path.
ParseSVGPath parses an SVG path data string.
PolarPoint returns a point from polar coordinates, with angle in radians CCW and radius the distance from (0,0).
PolylineFromPath returns a polyline from the given path by approximating it by linear line segments, i.e.
PolylineFromPathCoords returns a polyline from the given path from each of the start/end coordinates of the segments, i.e.
PrimitiveCell is a (primitive) cell used for tiling.
Rectangle returns a rectangle of width w and height h.
RectangleCell is a rectangular cell with width a and height b used for tiling.
RegularPolygon returns a regular polygon with radius r.
RegularStarPolygon returns a regular star polygon with radius r.
RGB returns a color given by red, green, and blue ∈ [0,255].
RGBA returns a color given by red, green, and blue ∈ [0,255] (non alpha premultiplied) and alpha ∈ [0,1].
RhombusCell is a rhombus cell with sides of length a at an angle of 120 degrees used for tiling.
RoundedRectangle returns a rectangle of width w and height h with rounded corners of radius r.
SquareCell is a square cell with sides of length a used for tiling.
StarPolygon returns a star polygon of n points with alternating radius R and r.
TileRectangle tiles the given cell (determines the axes along which cells are repeated) onto the rectangle dst (bounds of clipping path), where cells are filled by rectangle src (bounds of object to be tiled).
Triangle returns a triangle of radius r pointing upwards.

# Constants

Command values as powers of 2 so that the float64 representation is exact TODO: make CloseCmd a LineTo + CloseCmd, where CloseCmd is only a command value, no coordinates TODO: optimize command memory layout in paths: we need three bits to represent each command, thus 6 to specify command going forward and going backward.
see VerticalAlign.
see TextAlign.
See CoordSystem.
See CoordSystem.
See CoordSystem.
See CoordSystem.
see TextAlign.
Command values as powers of 2 so that the float64 representation is exact TODO: make CloseCmd a LineTo + CloseCmd, where CloseCmd is only a command value, no coordinates TODO: optimize command memory layout in paths: we need three bits to represent each command, thus 6 to specify command going forward and going backward.
Command values as powers of 2 so that the float64 representation is exact TODO: make CloseCmd a LineTo + CloseCmd, where CloseCmd is only a command value, no coordinates TODO: optimize command memory layout in paths: we need three bits to represent each command, thus 6 to specify command going forward and going backward.
DefaultResolution is the default resolution used for font PPEMs and is set to 96 DPI.
see FillRule.
900.
700.
see VerticalAlign.
800.
200.
see FontStyle.
300.
500.
see VerticalAlign.
see FontVariant.
400.
600.
see FontVariant.
see FontVariant.
see FontVariant.
100.
see VerticalAlign.
see WritingMode.
See ImageFit.
See ImageFit.
See ImageFit.
see TextAlign.
see TextAlign.
Command values as powers of 2 so that the float64 representation is exact TODO: make CloseCmd a LineTo + CloseCmd, where CloseCmd is only a command value, no coordinates TODO: optimize command memory layout in paths: we need three bits to represent each command, thus 6 to specify command going forward and going backward.
see ImageEncoding.
see ImageEncoding.
see TextAlign.
Command values as powers of 2 so that the float64 representation is exact TODO: make CloseCmd a LineTo + CloseCmd, where CloseCmd is only a command value, no coordinates TODO: optimize command memory layout in paths: we need three bits to represent each command, thus 6 to specify command going forward and going backward.
turn horizontal text 90deg clockwise for VerticalRL, and counter clockwise for VerticalLR.
see FillRule.
see FillRule.
see FillRule.
Command values as powers of 2 so that the float64 representation is exact TODO: make CloseCmd a LineTo + CloseCmd, where CloseCmd is only a command value, no coordinates TODO: optimize command memory layout in paths: we need three bits to represent each command, thus 6 to specify command going forward and going backward.
see TextAlign.
see TextAlign.
split characters and lay them out upright.
see WritingMode.
see WritingMode.

# Variables

Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
rgb(240, 248, 255).
rgb(250, 235, 215).
rgb(0, 255, 255).
rgb(127, 255, 212).
ArcsJoin connects two path elements by extending the ends of the paths as circle arcs until they meet.
rgb(240, 255, 255).
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
rgb(245, 245, 220).
BentleyOttmannEpsilon is the snap rounding grid used by the Bentley-Ottmann algorithm.
BevelJoin connects two path elements by a linear join.
rgb(255, 228, 196).
rgb(0, 0, 0).
rgb(255, 235, 205).
rgb(0, 0, 255).
rgb(138, 43, 226).
rgb(165, 42, 42).
rgb(222, 184, 135).
ButtCap caps the start or end of a path by a butt cap.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
rgb(95, 158, 160).
rgb(127, 255, 0).
rgb(210, 105, 30).
rgb(255, 127, 80).
rgb(100, 149, 237).
rgb(255, 248, 220).
rgb(220, 20, 60).
rgb(0, 255, 255).
Predefined paper sizes.
rgb(0, 0, 139).
rgb(0, 139, 139).
rgb(184, 134, 11).
rgb(169, 169, 169).
rgb(0, 100, 0).
rgb(169, 169, 169).
rgb(189, 183, 107).
rgb(139, 0, 139).
rgb(85, 107, 47).
rgb(255, 140, 0).
rgb(153, 50, 204).
rgb(139, 0, 0).
rgb(233, 150, 122).
rgb(143, 188, 143).
rgb(72, 61, 139).
rgb(47, 79, 79).
rgb(47, 79, 79).
rgb(0, 206, 209).
rgb(148, 0, 211).
Dash patterns.
Dash patterns.
rgb(255, 20, 147).
rgb(0, 191, 255).
DefaultColorSpace is set to LinearColorSpace to match other renderers.
DefaultStyle is the default style for paths.
Dash patterns.
Dash patterns.
Dash patterns.
rgb(105, 105, 105).
rgb(105, 105, 105).
rgb(30, 144, 255).
Dash patterns.
Epsilon is the smallest number below which we assume the value to be zero.
Predefined paper sizes.
FastStroke skips "settling" the resulting paths for Path.Offset and Path.Stroke, which ensures a well-formed path without overlapping nor holes.
rgb(178, 34, 34).
rgb(255, 250, 240).
FontDashedUnderline is a font decoration that draws a dashed line under the text.
FontDottedUnderline is a font decoration that draws a dotted line under the text.
FontDoubleUnderline is a font decoration that draws two lines under the text.
FontOverline is a font decoration that draws a line over the text.
FontSawtoothUnderline is a font decoration that draws a wavy sawtooth path under the text.
FontSineUnderline is a font decoration that draws a wavy sine path under the text.
FontStrikethrough is a font decoration that draws a line through the text.
FontUnderline is a font decoration that draws a line under the text.
FontWavyUnderline is a font decoration that draws a wavy path under the text.
rgb(34, 139, 34).
rgb(255, 0, 255).
rgb(220, 220, 220).
rgb(248, 248, 255).
rgb(255, 215, 0).
rgb(218, 165, 32).
rgb(128, 128, 128).
rgb(0, 128, 0).
rgb(173, 255, 47).
rgb(128, 128, 128).
rgb(240, 255, 240).
rgb(255, 105, 180).
Identity is the identity affine transformation matrix, i.e.
rgb(205, 92, 92).
rgb(75, 0, 130).
rgb(255, 255, 240).
rgb(240, 230, 140).
rgb(230, 230, 250).
rgb(255, 240, 245).
rgb(124, 252, 0).
Predefined paper sizes.
Predefined paper sizes.
rgb(255, 250, 205).
Predefined paper sizes.
rgb(173, 216, 230).
rgb(240, 128, 128).
rgb(224, 255, 255).
rgb(250, 250, 210).
rgb(211, 211, 211).
rgb(144, 238, 144).
rgb(211, 211, 211).
rgb(255, 182, 193).
rgb(255, 160, 122).
rgb(32, 178, 170).
rgb(135, 206, 250).
rgb(119, 136, 153).
rgb(119, 136, 153).
rgb(176, 196, 222).
rgb(255, 255, 224).
rgb(0, 255, 0).
rgb(50, 205, 50).
rgb(250, 240, 230).
rgb(255, 0, 255).
rgb(128, 0, 0).
rgb(102, 205, 170).
rgb(0, 0, 205).
rgb(186, 85, 211).
rgb(147, 112, 219).
rgb(60, 179, 113).
rgb(123, 104, 238).
rgb(0, 250, 154).
rgb(72, 209, 204).
rgb(199, 21, 133).
rgb(25, 25, 112).
rgb(245, 255, 250).
rgb(255, 228, 225).
TODO: should extend limit*halfwidth before bevel.
MiterJoin connects two path elements by extending the ends of the paths as lines until they meet.
rgb(255, 228, 181).
rgb(255, 222, 173).
rgb(0, 0, 128).
rgb(253, 245, 230).
rgb(128, 128, 0).
rgb(107, 142, 35).
rgb(255, 165, 0).
rgb(255, 69, 0).
rgb(218, 112, 214).
Origin is the coordinate system's origin.
rgb(238, 232, 170).
rgb(152, 251, 152).
rgb(175, 238, 238).
rgb(219, 112, 147).
rgb(255, 239, 213).
rgb(255, 218, 185).
rgb(205, 133, 63).
rgb(255, 192, 203).
PixelTolerance is the maximum deviation of the rasterized path from the original for flattening purposed in pixels.
rgb(221, 160, 221).
rgb(176, 224, 230).
Precision is the number of significant digits at which floating point value will be printed to output formats.
rgb(128, 0, 128).
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
rgb(255, 0, 0).
rgb(188, 143, 143).
RoundCap caps the start or end of a path by a round cap.
RoundJoin connects two path elements by a round join.
rgb(65, 105, 225).
rgb(139, 69, 19).
rgb(250, 128, 114).
rgb(244, 164, 96).
rgb(46, 139, 87).
rgb(255, 245, 238).
rgb(160, 82, 45).
rgb(192, 192, 192).
rgb(135, 206, 235).
rgb(106, 90, 205).
rgb(112, 128, 144).
rgb(112, 128, 144).
rgb(255, 250, 250).
Dash patterns.
Dash patterns.
Dash patterns.
Dash patterns.
rgb(0, 255, 127).
SquareCap caps the start or end of a path by a square cap.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
Predefined paper sizes.
rgb(70, 130, 180).
Predefined paper sizes.
rgb(210, 180, 140).
rgb(0, 128, 128).
rgb(216, 191, 216).
Tolerance is the maximum deviation from the original path in millimeters when e.g.
rgb(255, 99, 71).
rgba(0, 0, 0, 0).
rgb(64, 224, 208).
rgb(238, 130, 238).
rgb(245, 222, 179).
rgb(255, 255, 255).
rgb(245, 245, 245).
rgb(255, 255, 0).
rgb(154, 205, 50).

# Structs

ArcsJoiner is an arcs joiner.
BevelJoiner is a bevel joiner.
ButtCapper is a butt capper.
Canvas stores all drawing operations as layers that can be re-rendered to other renderers.
Context maintains the state for the current path, path style, and view transformation matrix.
ContextState defines the state of the context, including fill or stroke style, view and coordinate view.
Font defines an SFNT font such as TTF or OTF.
FontFace defines a font face from a given font.
FontFamily contains a family of fonts (bold, italic, ...).
FontMetrics contains a number of metrics that define a font face.
FontSubsetter holds a map between original glyph IDs and new glyph IDs in a subsetted font.
GammaColorSpace assumes that input colors and output images are gamma-corrected with the given gamma value.
Hatch pattern is a filling hatch pattern.
Image is a raster image.
Intersection is an intersection between two path segments, e.g.
LinearColorSpace is the default color space that does not do color space conversion for blending purposes.
LinearGradient is a linear gradient pattern between the given start and end points.
MiterJoiner is a miter joiner.
Paint is the type of paint used to fill or stroke a path.
Path defines a vector path in 2D using a series of commands (MoveTo, LineTo, QuadTo, CubeTo, ArcTo and Close).
PathReverseScanner scans the path in reverse order.
PathScanner scans the path.
Point is a coordinate in 2D space.
Polyline defines a list of points in 2D space that form a polyline.
RadialGradient is a radial gradient pattern between two circles defined by their center points and radii.
Rect is a rectangle in 2D defined by a position and its width and height.
RichText allows to build up a rich text with text spans of different font faces and fitting that into a box using Donald Knuth's line breaking algorithm.
RoundCapper is a round capper.
RoundJoiner is a round joiner.
Segment is a path command.
Size defines a size (width and height).
SquareCapper is a square capper.
SRGBColorSpace assumes that input colors and output images are in the sRGB color space (ubiquitous in almost all applications), which implies that for blending we need to convert to the linear color space, do blending, and then convert back to the sRGB color space.
Stop is a color and offset for gradient patterns.
Style is the path style that defines how to draw the path.
TODO: test performance versus (2,4)-tree (current LEDA implementation), (2,16)-tree (as proposed by S.
Text
Text holds the representation of a text object.
TextSpan is a span of text.
TextSpanObject is an object that can be used within a text span.

# Interfaces

Capper implements Cap, with rhs the path to append to, halfWidth the half width of the stroke, pivot the pivot point around which to construct a cap, and n0 the normal at the start of the path.
ColorSpace defines the color space within the RGB color model.
DVIFont draws a rune/glyph to the Pather at a position in millimeters.
DVIFonts gets a font according to its font name and font size in points.
FontDecorator is an interface that returns a path given a font face and a width in millimeters.
Gradient is a gradient pattern for filling.
Joiner implements Join, with rhs the right path and lhs the left path to append to, pivot the intersection of both path elements, n0 and n1 the normals at the start and end of the path respectively.
Renderer is an interface that renderers implement.

# Type aliases

CoordSystem is the coordinate system, which can be either of the four cartesian quadrants.
CSSColor is a string formatter to convert a color.RGBA to a CSS color (hexadecimal or using rgba()).
FillRule is the algorithm to specify which area is to be filled and which not, in particular when multiple subpaths overlap.
FontStyle defines the font style to be used for the font.
FontVariant defines the font variant to be used for the font, such as subscript or smallcaps.
Hatcher is a hatch pattern along the cell's axes.
ImageEncoding defines whether the embedded image shall be embedded as lossless (typically PNG) or lossy (typically JPG).
ImageFit specifies how an image should fit a rectangle.
Matrix is used for affine transformations, which are transformations such as translation, scaling, reflection, rotation, shear stretching.
Resolution is used for rasterizing.
Stops are the colors and offsets for gradient patterns, sorted by offset.
SweepEvents is a heap priority queue of sweep events.
TextAlign specifies how the text should align or whether it should be justified.
TextOrientation specifies how horizontal text should be oriented within vertical text, or how vertical-only text should be laid out in horizontal text.
VerticalAlign specifies how the object should align vertically when embedded in text.
Writer can write a canvas to a writer.
WritingMode specifies how the text lines should be laid out.