drawing

package
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 Go to latest Published: Apr 15, 2026 License: MIT Imports: 21 Imported by: 3

README

go-chart > drawing

The bulk of the code in this package is based on draw2d, but with significant modifications to make the APIs more golang friendly and careful about units (points vs. pixels).

Documentation

Index

Constants

View Source 
const (
	// CurveRecursionLimit represents the maximum recursion that is really necessary to subsivide a curve into straight lines
	CurveRecursionLimit = 32
)

Variables

View Source 
var (
	// ColorTransparent is a fully transparent color.
	ColorTransparent = Color{R: 255, G: 255, B: 255, A: 0}
	// ColorWhite is R: 255, G: 255, B: 255.
	ColorWhite = Color{R: 255, G: 255, B: 255, A: 255}
	// ColorBlack is R: 0, G: 0, B: 0.
	ColorBlack = Color{R: 0, G: 0, B: 0, A: 255}
	// ColorGray is R: 128, G: 128, B: 128.
	ColorGray = Color{R: 128, G: 128, B: 128, A: 255}
	// ColorRed is R: 255, G: 0, B: 0.
	ColorRed = Color{R: 255, G: 0, B: 0, A: 255}
	// ColorGreen is R: 0, G: 128, B: 0.
	ColorGreen = Color{R: 0, G: 128, B: 0, A: 255}
	// ColorBlue is R: 0, G: 0, B: 255.
	ColorBlue = Color{R: 0, G: 0, B: 255, A: 255}
	// ColorSilver is R: 192, G: 192, B: 192.
	ColorSilver = Color{R: 192, G: 192, B: 192, A: 255}
	// ColorMaroon is R: 128, G: 0, B: 0.
	ColorMaroon = Color{R: 128, G: 0, B: 0, A: 255}
	// ColorPurple is R: 128, G: 0, B: 128.
	ColorPurple = Color{R: 128, G: 0, B: 128, A: 255}
	// ColorFuchsia is R: 255, G: 0, B: 255.
	ColorFuchsia = Color{R: 255, G: 0, B: 255, A: 255}
	// ColorLime is R: 0, G: 255, B: 0.
	ColorLime = Color{R: 0, G: 255, B: 0, A: 255}
	// ColorOlive is R: 128, G: 128, B: 0.
	ColorOlive = Color{R: 128, G: 128, B: 0, A: 255}
	// ColorYellow is R: 255, G: 255, B: 0.
	ColorYellow = Color{R: 255, G: 255, B: 0, A: 255}
	// ColorNavy is R: 0, G: 0, B: 128.
	ColorNavy = Color{R: 0, G: 0, B: 128, A: 255}
	// ColorTeal is R: 0, G: 128, B: 128.
	ColorTeal = Color{R: 0, G: 128, B: 128, A: 255}
	// ColorAqua is R: 0, G: 255, B: 255.
	ColorAqua = Color{R: 0, G: 255, B: 255, A: 255}

	// ColorLightGray is R: 211, G: 211, B: 211.
	ColorLightGray = Color{R: 211, G: 211, B: 211, A: 255}
	// ColorSlateGray is R: 112, G: 128, B: 144.
	ColorSlateGray = Color{R: 112, G: 128, B: 144, A: 255}
	// ColorLightSlateGray is R: 119, G: 136, B: 211.
	ColorLightSlateGray = Color{R: 119, G: 136, B: 211, A: 255}
	// ColorAzure is R: 240, G: 255, B: 255.
	ColorAzure = Color{R: 240, G: 255, B: 255, A: 255}
	// ColorBeige is R: 245, G: 245, B: 220.
	ColorBeige = Color{R: 245, G: 245, B: 220, A: 255}
	// ColorBrown is R: 165, G: 42, B: 42.
	ColorBrown = Color{R: 165, G: 42, B: 42, A: 255}
	// ColorChocolate is R: 210, G: 105, B: 30.
	ColorChocolate = Color{R: 210, G: 105, B: 30, A: 255}
	// ColorCoral is R: 255, G: 127, B: 80.
	ColorCoral = Color{R: 255, G: 127, B: 80, A: 255}
	// ColorLightCoral is R: 240, G: 128, B: 128.
	ColorLightCoral = Color{R: 240, G: 128, B: 128, A: 255}
	// ColorGold is R: 255, G: 215, B: 0.
	ColorGold = Color{R: 255, G: 215, B: 0, A: 255}
	// ColorIndigo is R: 75, G: 0, B: 130.
	ColorIndigo = Color{R: 75, G: 0, B: 130, A: 255}
	// ColorIvory is R: 255, G: 255, B: 250.
	ColorIvory = Color{R: 255, G: 255, B: 250, A: 255}
	// ColorOrange is R: 255, G: 165, B: 0.
	ColorOrange = Color{R: 255, G: 165, B: 0, A: 255}
	// ColorPink is R: 255, G: 192, B: 203.
	ColorPink = Color{R: 255, G: 192, B: 203, A: 255}
	// ColorPlum is R: 221, G: 160, B: 221.
	ColorPlum = Color{R: 221, G: 160, B: 221, A: 255}
	// ColorSalmon is R: 250, G: 128, B: 114.
	ColorSalmon = Color{R: 250, G: 128, B: 114, A: 255}
	// ColorTan is R: 210, G: 180, B: 140.
	ColorTan = Color{R: 210, G: 180, B: 140, A: 255}
	// ColorKhaki is R: 240, G: 230, B: 140.
	ColorKhaki = Color{R: 240, G: 230, B: 140, A: 255}
	// ColorTurquoise is R: 64, G: 224, B: 208.
	ColorTurquoise = Color{R: 64, G: 224, B: 208, A: 255}
	// ColorViolet is R: 238, G: 130, B: 238.
	ColorViolet = Color{R: 238, G: 130, B: 238, A: 255}
	// ColorSkyBlue is R: 135, G: 206, B: 235.
	ColorSkyBlue = Color{R: 135, G: 206, B: 235, A: 255}
	// ColorLavender is R: 230, G: 230, B: 250.
	ColorLavender = Color{R: 230, G: 230, B: 250, A: 255}
	// ColorThistle is R: 216, G: 191, B: 216.
	ColorThistle = Color{R: 216, G: 191, B: 216, A: 255}
)

Basic Colors from: https://www.w3.org/wiki/CSS/Properties/color/keywords

View Source 
var FallbackFonts = []string{"notosans", "notosans-chartsymbols", "roboto"}

FallbackFonts is the ordered list of fallback fonts to try when a character is missing.

Functions

func Bresenham 

func Bresenham(img draw.Image, color color.Color, x0, y0, x1, y1 int)

Bresenham draws a line between (x0, y0) and (x1, y1)

func ColorChannelFromFloat 

func ColorChannelFromFloat(v float64) uint8

ColorChannelFromFloat returns a normalized byte from a given float value.

func DrawContour 

func DrawContour(path PathBuilder, ps []truetype.Point, dx, dy float64)

DrawContour draws the given closed contour at the given sub-pixel offset.

func DrawImage 

func DrawImage(src image.Image, dest draw.Image, tr Matrix, op draw.Op, filter ImageFilter)

DrawImage draws an image into dest using an affine transformation matrix, an op and a filter.

func Flatten 

func Flatten(path *Path, flattener Flattener, scale float64)

Flatten convert curves into straight segments keeping join segments info.

func GetFont added in v0.5.17 

func GetFont(fontFamily string) *truetype.Font

GetFont get the font by font family or nil if the family is not installed.

func InstallFont added in v0.5.17 

func InstallFont(fontFamily string, data []byte) error

InstallFont installs the font in the global registry.

func PointsToPixels 

func PointsToPixels(dpi, points float64) (pixels float64)

PointsToPixels returns the pixels for a given number of points at a DPI.

func PolylineBresenham 

func PolylineBresenham(img draw.Image, c color.Color, s ...float64)

PolylineBresenham draws a polyline to an image

func SubdivideCubic 

func SubdivideCubic(c, c1, c2 []float64)

SubdivideCubic a Bezier cubic curve in 2 equivalents Bezier cubic curves. c1 and c2 parameters are the resulting curves

func SubdivideQuad 

func SubdivideQuad(c, c1, c2 []float64)

SubdivideQuad a Bezier quad curve in 2 equivalents Bezier quad curves. c1 and c2 parameters are the resulting curves

func TraceArc 

func TraceArc(t Liner, x, y, rx, ry, start, angle, scale float64) (lastX, lastY float64)

TraceArc trace an arc using a Liner

func TraceCubic 

func TraceCubic(t Liner, cubic []float64, flatteningThreshold float64)

TraceCubic generate lines subdividing the cubic curve using a Liner flattening_threshold helps determines the flattening expectation of the curve

func TraceQuad 

func TraceQuad(t Liner, quad []float64, flatteningThreshold float64)

TraceQuad generate lines subdividing the curve using a Liner flattening_threshold helps determines the flattening expectation of the curve

Types

type Color 

type Color struct {
	R, G, B, A uint8
}

Color is our internal color type because color.Color is bullshit.

func ColorFromAlphaMixedRGBA 

func ColorFromAlphaMixedRGBA(r, g, b, a uint32) Color

ColorFromAlphaMixedRGBA returns the system alpha mixed rgba values.

func ColorFromHex 

func ColorFromHex(hex string) Color

ColorFromHex returns a color from a css hex code.

NOTE: it will trim a leading '#' character if present.

func ColorFromKnown 

func ColorFromKnown(known string) Color

ColorFromKnown returns an internal color from a known (basic) color name.

func ColorFromRGBA 

func ColorFromRGBA(color string) Color

ColorFromRGBA returns a color from a `rgb(i,i,i)` or `rgba(i,i,i,f)` css function.

func ParseColor 

func ParseColor(rawColor string) Color

ParseColor parses a color from a string.

func (Color) AverageWith 

func (c Color) AverageWith(other Color) Color

AverageWith averages two colors.

func (Color) Equals 

func (c Color) Equals(other Color) bool

Equals returns true if the color equals another.

func (Color) HSL added in v0.5.0 

func (c Color) HSL() (h, s, l float64)

HSL converts outputs the color HSL (hue, saturation, lightness). H in degrees, S and L in [0,1].

func (Color) IsTransparent 

func (c Color) IsTransparent() bool

IsTransparent returns if the colors alpha channel is zero.

func (Color) IsZero 

func (c Color) IsZero() bool

IsZero returns if the color has been set or not.

func (Color) RGBA 

func (c Color) RGBA() (r, g, b, a uint32)

RGBA returns the color as a pre-alpha mixed color set.

func (Color) String 

func (c Color) String() string

String returns a CSS string representation of the color.

func (Color) StringRGB added in v0.4.0 

func (c Color) StringRGB() string

StringRGB returns a CSS RGB string representation of the color.

func (Color) StringRGBA added in v0.4.0 

func (c Color) StringRGBA() string

StringRGBA returns a CSS RGBA string representation of the color.

func (Color) WithAdjustHSL added in v0.5.0 

func (c Color) WithAdjustHSL(hueDelta, satDelta, lightDelta float64) Color

WithAdjustHSL adjusts the hue, saturation, and lightness of a color by given deltas. hueDelta is in degrees; satDelta and lightDelta are in the range [-1, 1].

func (Color) WithAlpha 

func (c Color) WithAlpha(a uint8) Color

WithAlpha returns a copy of the color with a given alpha.

type ContextStack 

type ContextStack struct {
	Tr          Matrix
	Path        *Path
	LineWidth   float64
	Dash        []float64
	DashOffset  float64
	StrokeColor color.Color
	FillColor   color.Color
	FillRule    FillRule

	FontSizePoints float64
	Font           *truetype.Font

	Scale float64

	Previous *ContextStack
}

ContextStack is a graphic context implementation.

type DashVertexConverter 

type DashVertexConverter struct {
	// contains filtered or unexported fields
}

DashVertexConverter is a converter for dash vertexes.

func NewDashVertexConverter 

func NewDashVertexConverter(dash []float64, dashOffset float64, flattener Flattener) *DashVertexConverter

NewDashVertexConverter creates a new dash converter.

func (*DashVertexConverter) End 

func (dasher *DashVertexConverter) End()

End forwards the completed path to the next converter (for PathBuilder interface).

func (*DashVertexConverter) LineTo 

func (dasher *DashVertexConverter) LineTo(x, y float64)

LineTo adds a dashed line segment to the path (for PathBuilder interface).

func (*DashVertexConverter) MoveTo 

func (dasher *DashVertexConverter) MoveTo(x, y float64)

MoveTo sets the starting point for the dashed path (for PathBuilder interface).

type DemuxFlattener 

type DemuxFlattener struct {
	Flatteners []Flattener
}

DemuxFlattener is a slice of Flattener.

func (DemuxFlattener) End 

func (dc DemuxFlattener) End()

End signals completion to all child flatteners (for PathBuilder interface).

func (DemuxFlattener) LineTo 

func (dc DemuxFlattener) LineTo(x, y float64)

LineTo forwards a line command to all child flatteners (for PathBuilder interface).

func (DemuxFlattener) MoveTo 

func (dc DemuxFlattener) MoveTo(x, y float64)

MoveTo forwards a move command to all child flatteners (for PathBuilder interface).

type FillRule 

type FillRule int

FillRule defines the type for fill rules 

const (
	// FillRuleEvenOdd determines the "insideness" of a point in the shape
	// by drawing a ray from that point to infinity in any direction
	// and counting the number of path segments from the given shape that the ray crosses.
	// If this number is odd, the point is inside; if even, the point is outside.
	FillRuleEvenOdd FillRule = iota
	// FillRuleWinding determines the "insideness" of a point in the shape
	// by drawing a ray from that point to infinity in any direction
	// and then examining the places where a segment of the shape crosses the ray.
	// Starting with a count of zero, add one each time a path segment crosses
	// the ray from left to right and subtract one each time
	// a path segment crosses the ray from right to left. After counting the crossings,
	// if the result is zero then the point is outside the path. Otherwise, it is inside.
	FillRuleWinding
)

type Flattener 

type Flattener interface {
	// MoveTo Start a New line from the point (x, y).
	MoveTo(x, y float64)
	// LineTo Draw a line from the current position to the point (x, y).
	LineTo(x, y float64)
	// End mark the current line as finished.
	End()
}

Flattener receive segment definition.

type FontExtents 

type FontExtents struct {
	// Ascent is the distance that the text
	// extends above the baseline.
	Ascent float64

	// Descent is the distance that the text
	// extends below the baseline.  The descent
	// is given as a negative value.
	Descent float64

	// Height is the distance from the lowest
	// descending point to the highest ascending
	// point.
	Height float64
}

FontExtents contains font metric information.

func Extents 

func Extents(font *truetype.Font, size float64) FontExtents

Extents returns the FontExtents for a font. TODO needs to read this https://developer.apple.com/fonts/TrueType-Reference-Manual/RM02/Chap2.html#intro

type FtLineBuilder 

type FtLineBuilder struct {
	Adder raster.Adder
}

FtLineBuilder is a builder for freetype raster glyphs.

func (FtLineBuilder) End 

func (liner FtLineBuilder) End()

End finalizes the current path (for PathBuilder interface).

func (FtLineBuilder) LineTo 

func (liner FtLineBuilder) LineTo(x, y float64)

LineTo adds a line segment from the current point to the specified point (for PathBuilder interface).

func (FtLineBuilder) MoveTo 

func (liner FtLineBuilder) MoveTo(x, y float64)

MoveTo starts a new segment at the given point (for PathBuilder interface).

type ImageFilter 

type ImageFilter int

ImageFilter defines the type of filter to use. 

const (
	// LinearFilter defines a linear filter.
	LinearFilter ImageFilter = iota
	// BilinearFilter defines a bilinear filter.
	BilinearFilter
	// BicubicFilter defines a bicubic filter.
	BicubicFilter
)

type LineStroker 

type LineStroker struct {
	Flattener     Flattener
	HalfLineWidth float64
	// contains filtered or unexported fields
}

LineStroker draws the stroke portion of a line.

func NewLineStroker 

func NewLineStroker(flattener Flattener) *LineStroker

NewLineStroker creates a new line stroker.

func (*LineStroker) End 

func (l *LineStroker) End()

End emits the completed stroked path to the next flattener (for PathBuilder interface).

func (*LineStroker) LineTo 

func (l *LineStroker) LineTo(x, y float64)

LineTo adds a stroked line to the path (for PathBuilder interface).

func (*LineStroker) MoveTo 

func (l *LineStroker) MoveTo(x, y float64)

MoveTo records the starting point for a stroked segment (for PathBuilder interface).

type Liner 

type Liner interface {
	// LineTo Draw a line from the current position to the point (x, y).
	LineTo(x, y float64)
}

Liner receive segment definition.

type Matrix 

type Matrix [6]float64

Matrix represents an affine transformation.

func NewIdentityMatrix 

func NewIdentityMatrix() Matrix

NewIdentityMatrix creates an identity transformation matrix.

func NewMatrixFromRects 

func NewMatrixFromRects(rectangle1, rectangle2 [4]float64) Matrix

NewMatrixFromRects creates a transformation matrix, combining a scale and a translation, that transform rectangle1 into rectangle2.

func NewRotationMatrix 

func NewRotationMatrix(angle float64) Matrix

NewRotationMatrix creates a rotation transformation matrix. angle is in radian.

func NewScaleMatrix 

func NewScaleMatrix(sx, sy float64) Matrix

NewScaleMatrix creates a transformation matrix with a sx, sy scale factor.

func NewTranslationMatrix 

func NewTranslationMatrix(tx, ty float64) Matrix

NewTranslationMatrix creates a transformation matrix with a translation tx and ty translation parameter.

func (*Matrix) Compose 

func (tr *Matrix) Compose(trToCompose Matrix)

Compose multiplies trToConcat x tr.

func (*Matrix) Copy 

func (tr *Matrix) Copy() Matrix

Copy copies the matrix.

func (*Matrix) Determinant 

func (tr *Matrix) Determinant() float64

Determinant computes the determinant of the matrix.

func (*Matrix) Equals 

func (tr *Matrix) Equals(tr2 Matrix) bool

Equals tests if a two transformation are equal. A tolerance is applied when comparing matrix elements.

func (*Matrix) GetScale 

func (tr *Matrix) GetScale() float64

GetScale computes a scale for the matrix.

func (*Matrix) GetScaling 

func (tr *Matrix) GetScaling() (x, y float64)

GetScaling gets the matrix scaling.

func (*Matrix) GetTranslation 

func (tr *Matrix) GetTranslation() (x, y float64)

GetTranslation gets the matrix translation.

func (*Matrix) Inverse 

func (tr *Matrix) Inverse()

Inverse computes the inverse matrix.

func (*Matrix) InverseTransform 

func (tr *Matrix) InverseTransform(points []float64)

InverseTransform applies the transformation inverse matrix to the rectangle represented by the min and the max point of the rectangle.

func (*Matrix) InverseTransformPoint 

func (tr *Matrix) InverseTransformPoint(x, y float64) (xres, yres float64)

InverseTransformPoint applies the transformation inverse matrix to point. It returns the point the transformed point.

func (*Matrix) IsIdentity 

func (tr *Matrix) IsIdentity() bool

IsIdentity tests if a transformation is the identity transformation. A tolerance is applied when comparing matrix elements.

func (*Matrix) IsTranslation 

func (tr *Matrix) IsTranslation() bool

IsTranslation tests if a transformation is a pure translation. A tolerance is applied when comparing matrix elements.

func (*Matrix) Rotate 

func (tr *Matrix) Rotate(radians float64)

Rotate adds a rotation to the matrix.

func (*Matrix) Scale 

func (tr *Matrix) Scale(sx, sy float64)

Scale adds a scale to the matrix.

func (*Matrix) Transform 

func (tr *Matrix) Transform(points []float64)

Transform applies the transformation matrix to points. It modifies the points passed in parameter.

func (*Matrix) TransformPoint 

func (tr *Matrix) TransformPoint(x, y float64) (xres, yres float64)

TransformPoint applies the transformation matrix to point. It returns the point the transformed point.

func (*Matrix) TransformRectangle 

func (tr *Matrix) TransformRectangle(x0, y0, x2, y2 float64) (nx0, ny0, nx2, ny2 float64)

TransformRectangle applies the transformation matrix to the rectangle represented by the min and the max point of the rectangle.

func (*Matrix) Translate 

func (tr *Matrix) Translate(tx, ty float64)

Translate adds a translation to the matrix.

func (*Matrix) VectorTransform 

func (tr *Matrix) VectorTransform(points []float64)

VectorTransform applies the transformation matrix to points without using the translation parameter of the affine matrix. It modifies the points passed in parameter.

type Painter 

type Painter interface {
	raster.Painter
	SetColor(color color.Color)
}

Painter implements the freetype raster.Painter and has a SetColor method like the RGBAPainter.

type Path 

type Path struct {
	// Components is a slice of PathComponent in a Path and mark the role of each points in the Path.
	Components []PathComponent
	// Points are combined with Components to have a specific role in the path.
	Points []float64
	// contains filtered or unexported fields
}

Path stores points.

func (*Path) ArcTo 

func (p *Path) ArcTo(cx, cy, rx, ry, startAngle, delta float64)

ArcTo adds an arc to the path.

func (*Path) Clear 

func (p *Path) Clear()

Clear reset the path.

func (*Path) Close 

func (p *Path) Close()

Close closes the current path.

func (*Path) Copy 

func (p *Path) Copy() (dest *Path)

Copy make a clone of the current path and return it.

func (*Path) CubicCurveTo 

func (p *Path) CubicCurveTo(cx1, cy1, cx2, cy2, x, y float64)

CubicCurveTo adds a cubic Bézier curve to the current path.

func (*Path) IsEmpty 

func (p *Path) IsEmpty() bool

IsEmpty returns true if the path is empty.

func (*Path) LastPoint 

func (p *Path) LastPoint() (x, y float64)

LastPoint returns the current point of the current path.

func (*Path) LineTo 

func (p *Path) LineTo(x, y float64)

LineTo adds a line to the current path.

func (*Path) MoveTo 

func (p *Path) MoveTo(x, y float64)

MoveTo starts a new path at (x, y) position.

func (*Path) QuadCurveTo 

func (p *Path) QuadCurveTo(cx, cy, x, y float64)

QuadCurveTo adds a quadratic Bézier curve to the current path.

func (*Path) String 

func (p *Path) String() string

String returns a debug text view of the path.

type PathBuilder 

type PathBuilder interface {
	// LastPoint returns the current point of the current sub path.
	LastPoint() (x, y float64)
	// MoveTo creates a new subpath that start at the specified point.
	MoveTo(x, y float64)
	// LineTo adds a line to the current subpath.
	LineTo(x, y float64)
	// QuadCurveTo adds a quadratic Bézier curve to the current subpath.
	QuadCurveTo(cx, cy, x, y float64)
	// CubicCurveTo adds a cubic Bézier curve to the current subpath.
	CubicCurveTo(cx1, cy1, cx2, cy2, x, y float64)
	// ArcTo adds an arc to the current subpath.
	ArcTo(cx, cy, rx, ry, startAngle, angle float64)
	// Close creates a line from the current point to the last MoveTo point (if different) and
	// mark the path as closed so the first and last lines join nicely.
	Close()
}

PathBuilder describes the interface for path drawing.

type PathComponent 

type PathComponent int

PathComponent represents a component of a path. 

const (
	// MoveToComponent is a MoveTo component in a Path.
	MoveToComponent PathComponent = iota
	// LineToComponent is a LineTo component in a Path.
	LineToComponent
	// QuadCurveToComponent is a QuadCurveTo component in a Path.
	QuadCurveToComponent
	// CubicCurveToComponent is a CubicCurveTo component in a Path.
	CubicCurveToComponent
	// ArcToComponent is a ArcTo component in a Path.
	ArcToComponent
	// CloseComponent is a LineTo component in a Path.
	CloseComponent
)

type RasterGraphicContext 

type RasterGraphicContext struct {
	*StackGraphicContext
	// contains filtered or unexported fields
}

RasterGraphicContext is the implementation of GraphicContext for a raster image.

func NewRasterGraphicContext 

func NewRasterGraphicContext(img *image.RGBA) *RasterGraphicContext

NewRasterGraphicContext creates a new Graphic context from an image.

func NewRasterGraphicContextWithPainter 

func NewRasterGraphicContextWithPainter(img draw.Image, painter Painter) *RasterGraphicContext

NewRasterGraphicContextWithPainter creates a new Graphic context from an image and a Painter (see Freetype-go).

func (*RasterGraphicContext) Clear 

func (rgc *RasterGraphicContext) Clear()

Clear fills the current canvas with a default transparent color.

func (*RasterGraphicContext) CreateStringPath 

func (rgc *RasterGraphicContext) CreateStringPath(s string, x, y float64) (cursor float64, err error)

CreateStringPath creates a path from the string s at x, y, and returns the string width. The text is placed so that the left edge of the em square of the first character of s and the baseline intersect at x, y. The majority of the affected pixels will be above and to the right of the point, but some may be below or to the left. For example, drawing a string that starts with a 'J' in an italic font may affect pixels below and left of the point.

func (*RasterGraphicContext) DrawImage 

func (rgc *RasterGraphicContext) DrawImage(img image.Image)

DrawImage draws the raster image in the current canvas.

func (*RasterGraphicContext) Fill 

func (rgc *RasterGraphicContext) Fill(paths ...*Path)

Fill fills the paths with the color specified by SetFillColor.

func (*RasterGraphicContext) FillRect added in v0.4.3 

func (rgc *RasterGraphicContext) FillRect(x1, y1, x2, y2 int)

FillRect draws a filled rectangle with the provided coordinates and the current set FillColor.

func (*RasterGraphicContext) FillStringAt deprecated 

func (rgc *RasterGraphicContext) FillStringAt(text string, x, y float64) (cursor float64, err error)

Deprecated: FillStringAt is deprecated, use CreateStringPath and then Fill, or open a GitHub issue requesting it to be maintained.

func (*RasterGraphicContext) FillStroke 

func (rgc *RasterGraphicContext) FillStroke(paths ...*Path)

FillStroke first fills the paths and then strokes them.

func (*RasterGraphicContext) GetDPI 

func (rgc *RasterGraphicContext) GetDPI() float64

GetDPI returns the resolution of the Image GraphicContext.

func (*RasterGraphicContext) GetFont 

func (rgc *RasterGraphicContext) GetFont() *truetype.Font

GetFont returns the font used to draw text.

func (*RasterGraphicContext) GetStringBounds 

func (rgc *RasterGraphicContext) GetStringBounds(s string) (left, top, right, bottom float64, err error)

GetStringBounds returns the approximate pixel bounds of a string.

func (*RasterGraphicContext) SetDPI 

func (rgc *RasterGraphicContext) SetDPI(dpi float64)

SetDPI sets the screen resolution in dots per inch.

func (*RasterGraphicContext) SetFont 

func (rgc *RasterGraphicContext) SetFont(font *truetype.Font)

SetFont sets the font used to draw text.

func (*RasterGraphicContext) SetFontSize 

func (rgc *RasterGraphicContext) SetFontSize(fontSizePoints float64)

SetFontSize sets the font size in points (as in “a 12 point font”).

func (*RasterGraphicContext) Stroke 

func (rgc *RasterGraphicContext) Stroke(paths ...*Path)

Stroke strokes the paths with the color specified by SetStrokeColor

func (*RasterGraphicContext) StrokeStringAt deprecated 

func (rgc *RasterGraphicContext) StrokeStringAt(text string, x, y float64) (cursor float64, err error)

Deprecated: StrokeStringAt is deprecated, it's expected that most usage is through Render.Text. It can be replaced with CreateStringPath and then Stroke, or open a GitHub issue requesting it to be maintained.

type SegmentedPath 

type SegmentedPath struct {
	Points []float64
}

SegmentedPath is a path of disparate point sections.

func (*SegmentedPath) End 

func (p *SegmentedPath) End()

End completes the current path segment (for PathBuilder interface).

func (*SegmentedPath) LineTo 

func (p *SegmentedPath) LineTo(x, y float64)

LineTo appends a point to the current path segment (for PathBuilder interface).

func (*SegmentedPath) MoveTo 

func (p *SegmentedPath) MoveTo(x, y float64)

MoveTo records the first point of a new segment (for PathBuilder interface).

type StackGraphicContext 

type StackGraphicContext struct {
	// contains filtered or unexported fields
}

StackGraphicContext is a context that does things.

func NewStackGraphicContext 

func NewStackGraphicContext() *StackGraphicContext

NewStackGraphicContext Create a new Graphic context from an image.

func (*StackGraphicContext) ArcTo 

func (gc *StackGraphicContext) ArcTo(cx, cy, rx, ry, startAngle, delta float64)

ArcTo draws an arc.

func (*StackGraphicContext) BeginPath 

func (gc *StackGraphicContext) BeginPath()

BeginPath starts a new path.

func (*StackGraphicContext) Close 

func (gc *StackGraphicContext) Close()

Close closes a path.

func (*StackGraphicContext) ComposeMatrixTransform 

func (gc *StackGraphicContext) ComposeMatrixTransform(tr Matrix)

ComposeMatrixTransform composes a transform into the current transform.

func (*StackGraphicContext) CubicCurveTo 

func (gc *StackGraphicContext) CubicCurveTo(cx1, cy1, cx2, cy2, x, y float64)

CubicCurveTo draws a cubic curve.

func (*StackGraphicContext) GetFont 

func (gc *StackGraphicContext) GetFont() *truetype.Font

GetFont returns the font.

func (*StackGraphicContext) GetFontSize 

func (gc *StackGraphicContext) GetFontSize() float64

GetFontSize gets the font size.

func (*StackGraphicContext) GetMatrixTransform 

func (gc *StackGraphicContext) GetMatrixTransform() Matrix

GetMatrixTransform returns the matrix transform.

func (*StackGraphicContext) IsEmpty 

func (gc *StackGraphicContext) IsEmpty() bool

IsEmpty returns if the path is empty.

func (*StackGraphicContext) LastPoint 

func (gc *StackGraphicContext) LastPoint() (x float64, y float64)

LastPoint returns the last point on the path.

func (*StackGraphicContext) LineTo 

func (gc *StackGraphicContext) LineTo(x, y float64)

LineTo draws a line.

func (*StackGraphicContext) MoveTo 

func (gc *StackGraphicContext) MoveTo(x, y float64)

MoveTo moves the cursor for a path.

func (*StackGraphicContext) QuadCurveTo 

func (gc *StackGraphicContext) QuadCurveTo(cx, cy, x, y float64)

QuadCurveTo draws a quad curve.

func (*StackGraphicContext) Restore 

func (gc *StackGraphicContext) Restore()

Restore restores the previous context.

func (*StackGraphicContext) Rotate 

func (gc *StackGraphicContext) Rotate(angle float64)

Rotate rotates the matrix transform by an angle in degrees.

func (*StackGraphicContext) Save 

func (gc *StackGraphicContext) Save()

Save pushes a context onto the stack.

func (*StackGraphicContext) Scale 

func (gc *StackGraphicContext) Scale(sx, sy float64)

Scale scales a transform.

func (*StackGraphicContext) SetFillColor 

func (gc *StackGraphicContext) SetFillColor(c color.Color)

SetFillColor sets the fill color.

func (*StackGraphicContext) SetFillRule 

func (gc *StackGraphicContext) SetFillRule(f FillRule)

SetFillRule sets the fill rule.

func (*StackGraphicContext) SetFont 

func (gc *StackGraphicContext) SetFont(f *truetype.Font)

SetFont sets the current font.

func (*StackGraphicContext) SetFontSize 

func (gc *StackGraphicContext) SetFontSize(fontSizePoints float64)

SetFontSize sets the font size.

func (*StackGraphicContext) SetLineDash 

func (gc *StackGraphicContext) SetLineDash(dash []float64, dashOffset float64)

SetLineDash sets the line dash.

func (*StackGraphicContext) SetLineWidth 

func (gc *StackGraphicContext) SetLineWidth(lineWidth float64)

SetLineWidth sets the line width.

func (*StackGraphicContext) SetMatrixTransform 

func (gc *StackGraphicContext) SetMatrixTransform(tr Matrix)

SetMatrixTransform sets the matrix transform.

func (*StackGraphicContext) SetStrokeColor 

func (gc *StackGraphicContext) SetStrokeColor(c color.Color)

SetStrokeColor sets the stroke color.

func (*StackGraphicContext) Translate 

func (gc *StackGraphicContext) Translate(tx, ty float64)

Translate translates a transform.

type Transformer 

type Transformer struct {
	Tr        Matrix
	Flattener Flattener
}

Transformer apply the Matrix transformation.

func (Transformer) End 

func (t Transformer) End()

End finishes the transformed path (for PathBuilder interface).

func (Transformer) LineTo 

func (t Transformer) LineTo(x, y float64)

LineTo transforms and forwards a line command (for PathBuilder interface).

func (Transformer) MoveTo 

func (t Transformer) MoveTo(x, y float64)

MoveTo transforms and passes a move command downstream (for PathBuilder interface).

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