unipdf/render/internal/context/imagerender/context.go

/*
 * This file is subject to the terms and conditions defined in
 * file 'LICENSE.md', which is part of this source code package.
 */

package imagerender

import (
	"errors"
	"image"
	"image/color"
	"math"

	"github.com/golang/freetype/raster"
	"golang.org/x/image/draw"
	"golang.org/x/image/font"
	"golang.org/x/image/math/f64"

	"github.com/unidoc/unipdf/v3/internal/transform"
	"github.com/unidoc/unipdf/v3/render/internal/context"
)

var (
	defaultFillStyle   = newSolidPattern(color.White)
	defaultStrokeStyle = newSolidPattern(color.Black)
)

// Context represents an image rendering context.
type Context struct {
	width         int
	height        int
	rasterizer    *raster.Rasterizer
	im            *image.RGBA
	mask          *image.Alpha
	color         color.Color
	fillPattern   context.Pattern
	strokePattern context.Pattern
	strokePath    raster.Path
	fillPath      raster.Path
	start         transform.Point
	current       transform.Point
	hasCurrent    bool
	dashes        []float64
	dashOffset    float64
	lineWidth     float64
	lineCap       context.LineCap
	lineJoin      context.LineJoin
	fillRule      context.FillRule
	matrix        transform.Matrix
	textState     *context.TextState
	stack         []*Context
}

// NewContext creates a new image.RGBA with the specified width and height
// and prepares a context for rendering onto that image.
func NewContext(width, height int) *Context {
	return NewContextForRGBA(image.NewRGBA(image.Rect(0, 0, width, height)))
}

// NewContextForImage copies the specified image into a new image.RGBA
// and prepares a context for rendering onto that image.
func NewContextForImage(im image.Image) *Context {
	return NewContextForRGBA(imageToRGBA(im))
}

// NewContextForRGBA prepares a context for rendering onto the specified image.
// No copy is made.
func NewContextForRGBA(im *image.RGBA) *Context {
	w := im.Bounds().Size().X
	h := im.Bounds().Size().Y

	return &Context{
		width:         w,
		height:        h,
		rasterizer:    raster.NewRasterizer(w, h),
		im:            im,
		color:         color.Transparent,
		fillPattern:   defaultFillStyle,
		strokePattern: defaultStrokeStyle,
		lineWidth:     1,
		fillRule:      context.FillRuleWinding,
		matrix:        transform.IdentityMatrix(),
		textState:     context.NewTextState(),
	}
}

// Image returns the image that has been drawn by this context.
func (dc *Context) Image() image.Image {
	return dc.im
}

// Width returns the width of the image in pixels.
func (dc *Context) Width() int {
	return dc.width
}

// Height returns the height of the image in pixels.
func (dc *Context) Height() int {
	return dc.height
}

// SetDash sets the current dash pattern to use. Call with zero arguments to
// disable dashes. The values specify the lengths of each dash, with
// alternating on and off lengths.
func (dc *Context) SetDash(dashes ...float64) {
	dc.dashes = dashes
}

// SetDashOffset sets the initial offset into the dash pattern to use when
// stroking dashed paths.
func (dc *Context) SetDashOffset(offset float64) {
	dc.dashOffset = offset
}

// LineWidth returns the line width of the context.
func (dc *Context) LineWidth() float64 {
	return dc.lineWidth
}

// SetLineWidth sets the line width of the context.
func (dc *Context) SetLineWidth(lineWidth float64) {
	dc.lineWidth = lineWidth
}

// SetLineCap sets the line cap style.
func (dc *Context) SetLineCap(lineCap context.LineCap) {
	dc.lineCap = lineCap
}

// SetLineJoin sets the line join style.
func (dc *Context) SetLineJoin(lineJoin context.LineJoin) {
	dc.lineJoin = lineJoin
}

// SetFillRule sets the fill rule.
func (dc *Context) SetFillRule(fillRule context.FillRule) {
	dc.fillRule = fillRule
}

//
// Color setters
//

func (dc *Context) setFillAndStrokeColor(c color.Color) {
	dc.color = c
	dc.fillPattern = newSolidPattern(c)
	dc.strokePattern = newSolidPattern(c)
}

// SetFillStyle sets current fill style
func (dc *Context) SetFillStyle(pattern context.Pattern) {
	// if pattern is SolidPattern, also change dc.color(for dc.Clear, dc.drawString)
	if fillStyle, ok := pattern.(*solidPattern); ok {
		dc.color = fillStyle.color
	}
	dc.fillPattern = pattern
}

// SetStrokeStyle sets current stroke style
func (dc *Context) SetStrokeStyle(pattern context.Pattern) {
	dc.strokePattern = pattern
}

// SetColor sets the current color(for both fill and stroke).
func (dc *Context) SetColor(c color.Color) {
	dc.setFillAndStrokeColor(c)
}

// SetStrokeRGBA sets the current color for stroking operations.
// r, g, b, a values must be in range 0-1.
func (dc *Context) SetStrokeRGBA(r, g, b, a float64) {
	color := color.NRGBA{
		uint8(r * 255),
		uint8(g * 255),
		uint8(b * 255),
		uint8(a * 255),
	}
	dc.strokePattern = newSolidPattern(color)
}

// SetFillRGBA sets the current color for fill operations.
// r, g, b, a values must be in range 0-1.
func (dc *Context) SetFillRGBA(r, g, b, a float64) {
	color := color.NRGBA{
		uint8(r * 255),
		uint8(g * 255),
		uint8(b * 255),
		uint8(a * 255),
	}
	dc.color = color
	dc.fillPattern = newSolidPattern(color)
}

// SetHexColor sets the current color using a hex string. The leading pound
// sign (#) is optional. Both 3- and 6-digit variations are supported. 8 digits
// may be provided to set the alpha value as well.
func (dc *Context) SetHexColor(x string) {
	r, g, b, a := parseHexColor(x)
	dc.SetRGBA255(r, g, b, a)
}

// SetRGBA255 sets the current color. r, g, b, a values should be between 0 and
// 255, inclusive.
func (dc *Context) SetRGBA255(r, g, b, a int) {
	dc.color = color.NRGBA{uint8(r), uint8(g), uint8(b), uint8(a)}
	dc.setFillAndStrokeColor(dc.color)
}

// SetRGB255 sets the current color. r, g, b values should be between 0 and 255,
// inclusive. Alpha will be set to 255 (fully opaque).
func (dc *Context) SetRGB255(r, g, b int) {
	dc.SetRGBA255(r, g, b, 255)
}

// SetRGBA sets the current color. r, g, b, a values should be between 0 and 1,
// inclusive.
func (dc *Context) SetRGBA(r, g, b, a float64) {
	dc.color = color.NRGBA{
		uint8(r * 255),
		uint8(g * 255),
		uint8(b * 255),
		uint8(a * 255),
	}
	dc.setFillAndStrokeColor(dc.color)
}

// SetRGB sets the current color. r, g, b values should be between 0 and 1,
// inclusive. Alpha will be set to 1 (fully opaque).
func (dc *Context) SetRGB(r, g, b float64) {
	dc.SetRGBA(r, g, b, 1)
}

//
// Path manipulation
//

// MoveTo starts a new subpath within the current path starting at the
// specified point.
func (dc *Context) MoveTo(x, y float64) {
	if dc.hasCurrent {
		dc.fillPath.Add1(fixedPoint(dc.start))
	}

	x, y = dc.Transform(x, y)
	p := transform.NewPoint(x, y)
	fp := fixedPoint(p)

	dc.strokePath.Start(fp)
	dc.fillPath.Start(fp)
	dc.start = p
	dc.current = p
	dc.hasCurrent = true
}

// LineTo adds a line segment to the current path starting at the current
// point. If there is no current point, it is equivalent to MoveTo(x, y)
func (dc *Context) LineTo(x, y float64) {
	if !dc.hasCurrent {
		dc.MoveTo(x, y)
	} else {
		x, y = dc.Transform(x, y)
		p := transform.NewPoint(x, y)
		fp := fixedPoint(p)

		dc.strokePath.Add1(fp)
		dc.fillPath.Add1(fp)
		dc.current = p
	}
}

// QuadraticTo adds a quadratic bezier curve to the current path starting at
// the current point. If there is no current point, it first performs
// MoveTo(x1, y1)
func (dc *Context) QuadraticTo(x1, y1, x2, y2 float64) {
	if !dc.hasCurrent {
		dc.MoveTo(x1, y1)
	}

	x1, y1 = dc.Transform(x1, y1)
	x2, y2 = dc.Transform(x2, y2)
	p1 := transform.NewPoint(x1, y1)
	p2 := transform.NewPoint(x2, y2)
	fp1 := fixedPoint(p1)
	fp2 := fixedPoint(p2)

	dc.strokePath.Add2(fp1, fp2)
	dc.fillPath.Add2(fp1, fp2)
	dc.current = p2
}

// CubicTo adds a cubic bezier curve to the current path starting at the
// current point. If there is no current point, it first performs
// MoveTo(x1, y1). Because freetype/raster does not support cubic beziers,
// this is emulated with many small line segments.
func (dc *Context) CubicTo(x1, y1, x2, y2, x3, y3 float64) {
	if !dc.hasCurrent {
		dc.MoveTo(x1, y1)
	}
	x0, y0 := dc.current.X, dc.current.Y
	x1, y1 = dc.Transform(x1, y1)
	x2, y2 = dc.Transform(x2, y2)
	x3, y3 = dc.Transform(x3, y3)
	points := cubicBezier(x0, y0, x1, y1, x2, y2, x3, y3)
	previous := fixedPoint(dc.current)
	for _, p := range points[1:] {
		f := fixedPoint(p)
		if f == previous {
			// TODO: this fixes some rendering issues but not all
			continue
		}
		previous = f
		dc.strokePath.Add1(f)
		dc.fillPath.Add1(f)
		dc.current = p
	}
}

// ClosePath adds a line segment from the current point to the beginning
// of the current subpath. If there is no current point, this is a no-op.
func (dc *Context) ClosePath() {
	if dc.hasCurrent {
		fp := fixedPoint(dc.start)
		dc.strokePath.Add1(fp)
		dc.fillPath.Add1(fp)
		dc.current = dc.start
	}
}

// ClearPath clears the current path. There is no current point after this
// operation.
func (dc *Context) ClearPath() {
	dc.strokePath.Clear()
	dc.fillPath.Clear()
	dc.hasCurrent = false
}

// NewSubPath starts a new subpath within the current path. There is no current
// point after this operation.
func (dc *Context) NewSubPath() {
	if dc.hasCurrent {
		dc.fillPath.Add1(fixedPoint(dc.start))
	}
	dc.hasCurrent = false
}

//
// Path drawing
//

func (dc *Context) capper() raster.Capper {
	switch dc.lineCap {
	case context.LineCapButt:
		return raster.ButtCapper
	case context.LineCapRound:
		return raster.RoundCapper
	case context.LineCapSquare:
		return raster.SquareCapper
	}
	return nil
}

func (dc *Context) joiner() raster.Joiner {
	switch dc.lineJoin {
	case context.LineJoinBevel:
		return raster.BevelJoiner
	case context.LineJoinRound:
		return raster.RoundJoiner
	}
	return nil
}

func (dc *Context) stroke(painter raster.Painter) {
	path := dc.strokePath
	if len(dc.dashes) > 0 {
		path = dashed(path, dc.dashes, dc.dashOffset)
	} else {
		// TODO: this is a temporary workaround to remove tiny segments
		// that result in rendering issues
		path = rasterPath(flattenPath(path))
	}
	r := dc.rasterizer
	r.UseNonZeroWinding = true
	r.Clear()
	r.AddStroke(path, fix(dc.lineWidth), dc.capper(), dc.joiner())
	r.Rasterize(painter)
}

func (dc *Context) fill(painter raster.Painter) {
	path := dc.fillPath
	if dc.hasCurrent {
		path = make(raster.Path, len(dc.fillPath))
		copy(path, dc.fillPath)
		path.Add1(fixedPoint(dc.start))
	}
	r := dc.rasterizer
	r.UseNonZeroWinding = dc.fillRule == context.FillRuleWinding
	r.Clear()
	r.AddPath(path)
	r.Rasterize(painter)
}

// StrokePreserve strokes the current path with the current color, line width,
// line cap, line join and dash settings. The path is preserved after this
// operation.
func (dc *Context) StrokePreserve() {
	var painter raster.Painter
	if dc.mask == nil {
		if pattern, ok := dc.strokePattern.(*solidPattern); ok {
			// with a nil mask and a solid color pattern, we can be more efficient
			// TODO: refactor so we don't have to do this type assertion stuff?
			p := raster.NewRGBAPainter(dc.im)
			p.SetColor(pattern.color)
			painter = p
		}
	}
	if painter == nil {
		painter = newPatternPainter(dc.im, dc.mask, dc.strokePattern)
	}
	dc.stroke(painter)
}

// Stroke strokes the current path with the current color, line width,
// line cap, line join and dash settings. The path is cleared after this
// operation.
func (dc *Context) Stroke() {
	dc.StrokePreserve()
	dc.ClearPath()
}

// FillPreserve fills the current path with the current color. Open subpaths
// are implicity closed. The path is preserved after this operation.
func (dc *Context) FillPreserve() {
	var painter raster.Painter
	if dc.mask == nil {
		if pattern, ok := dc.fillPattern.(*solidPattern); ok {
			// with a nil mask and a solid color pattern, we can be more efficient
			// TODO: refactor so we don't have to do this type assertion stuff?
			p := raster.NewRGBAPainter(dc.im)
			p.SetColor(pattern.color)
			painter = p
		}
	}
	if painter == nil {
		painter = newPatternPainter(dc.im, dc.mask, dc.fillPattern)
	}
	dc.fill(painter)
}

// Fill fills the current path with the current color. Open subpaths
// are implicity closed. The path is cleared after this operation.
func (dc *Context) Fill() {
	dc.FillPreserve()
	dc.ClearPath()
}

// ClipPreserve updates the clipping region by intersecting the current
// clipping region with the current path as it would be filled by dc.Fill().
// The path is preserved after this operation.
func (dc *Context) ClipPreserve() {
	clip := image.NewAlpha(image.Rect(0, 0, dc.width, dc.height))
	painter := raster.NewAlphaOverPainter(clip)
	dc.fill(painter)
	if dc.mask == nil {
		dc.mask = clip
	} else {
		mask := image.NewAlpha(image.Rect(0, 0, dc.width, dc.height))
		draw.DrawMask(mask, mask.Bounds(), clip, image.ZP, dc.mask, image.ZP, draw.Over)
		dc.mask = mask
	}
}

// SetMask allows you to directly set the *image.Alpha to be used as a clipping
// mask. It must be the same size as the context, else an error is returned
// and the mask is unchanged.
func (dc *Context) SetMask(mask *image.Alpha) error {
	if mask.Bounds().Size() != dc.im.Bounds().Size() {
		return errors.New("mask size must match context size")
	}
	dc.mask = mask
	return nil
}

// AsMask returns an *image.Alpha representing the alpha channel of this
// context. This can be useful for advanced clipping operations where you first
// render the mask geometry and then use it as a mask.
func (dc *Context) AsMask() *image.Alpha {
	mask := image.NewAlpha(dc.im.Bounds())
	draw.Draw(mask, dc.im.Bounds(), dc.im, image.ZP, draw.Src)
	return mask
}

// InvertMask inverts the alpha values in the current clipping mask such that
// a fully transparent region becomes fully opaque and vice versa.
func (dc *Context) InvertMask() {
	if dc.mask == nil {
		dc.mask = image.NewAlpha(dc.im.Bounds())
	} else {
		for i, a := range dc.mask.Pix {
			dc.mask.Pix[i] = 255 - a
		}
	}
}

// Clip updates the clipping region by intersecting the current
// clipping region with the current path as it would be filled by dc.Fill().
// The path is cleared after this operation.
func (dc *Context) Clip() {
	dc.ClipPreserve()
	dc.ClearPath()
}

// ResetClip clears the clipping region.
func (dc *Context) ResetClip() {
	dc.mask = nil
}

//
// Drawing operations
//

// Clear fills the entire image with the current color.
func (dc *Context) Clear() {
	src := image.NewUniform(dc.color)
	draw.Draw(dc.im, dc.im.Bounds(), src, image.ZP, draw.Src)
}

// SetPixel sets the color of the specified pixel using the current color.
func (dc *Context) SetPixel(x, y int) {
	dc.im.Set(x, y, dc.color)
}

// DrawPoint is like DrawCircle but ensures that a circle of the specified
// size is drawn regardless of the current transformation matrix. The position
// is still transformed, but not the shape of the point.
func (dc *Context) DrawPoint(x, y, r float64) {
	dc.Push()
	tx, ty := dc.Transform(x, y)
	dc.Identity()
	dc.DrawCircle(tx, ty, r)
	dc.Pop()
}

// DrawLine draws the line described by points x1,y1 and x2,y2.
func (dc *Context) DrawLine(x1, y1, x2, y2 float64) {
	dc.MoveTo(x1, y1)
	dc.LineTo(x2, y2)
}

// DrawRectangle draws a rectangle of size w,h at position x,y.
func (dc *Context) DrawRectangle(x, y, w, h float64) {
	dc.NewSubPath()
	dc.MoveTo(x, y)
	dc.LineTo(x+w, y)
	dc.LineTo(x+w, y+h)
	dc.LineTo(x, y+h)
	dc.ClosePath()
}

// DrawRoundedRectangle draws a rounded rectangle of size w,h at position x,y.
func (dc *Context) DrawRoundedRectangle(x, y, w, h, r float64) {
	x0, x1, x2, x3 := x, x+r, x+w-r, x+w
	y0, y1, y2, y3 := y, y+r, y+h-r, y+h
	dc.NewSubPath()
	dc.MoveTo(x1, y0)
	dc.LineTo(x2, y0)
	dc.DrawArc(x2, y1, r, degreesToRadians(270), degreesToRadians(360))
	dc.LineTo(x3, y2)
	dc.DrawArc(x2, y2, r, degreesToRadians(0), degreesToRadians(90))
	dc.LineTo(x1, y3)
	dc.DrawArc(x1, y2, r, degreesToRadians(90), degreesToRadians(180))
	dc.LineTo(x0, y1)
	dc.DrawArc(x1, y1, r, degreesToRadians(180), degreesToRadians(270))
	dc.ClosePath()
}

// DrawArc draws an arc described by r, angle1, angle2 at position x,y.
func (dc *Context) DrawArc(x, y, r, angle1, angle2 float64) {
	dc.DrawEllipticalArc(x, y, r, r, angle1, angle2)
}

// DrawEllipticalArc draws an elliptical arc described by r, angle1, angle2 at
// position x,y.
func (dc *Context) DrawEllipticalArc(x, y, rx, ry, angle1, angle2 float64) {
	const n = 16
	for i := 0; i < n; i++ {
		p1 := float64(i+0) / n
		p2 := float64(i+1) / n
		a1 := angle1 + (angle2-angle1)*p1
		a2 := angle1 + (angle2-angle1)*p2
		x0 := x + rx*math.Cos(a1)
		y0 := y + ry*math.Sin(a1)
		x1 := x + rx*math.Cos((a1+a2)/2)
		y1 := y + ry*math.Sin((a1+a2)/2)
		x2 := x + rx*math.Cos(a2)
		y2 := y + ry*math.Sin(a2)
		cx := 2*x1 - x0/2 - x2/2
		cy := 2*y1 - y0/2 - y2/2
		if i == 0 {
			if dc.hasCurrent {
				dc.LineTo(x0, y0)
			} else {
				dc.MoveTo(x0, y0)
			}
		}
		dc.QuadraticTo(cx, cy, x2, y2)
	}
}

// DrawEllipse draws an ellipse of size rx,ry at position x,y.
func (dc *Context) DrawEllipse(x, y, rx, ry float64) {
	dc.NewSubPath()
	dc.DrawEllipticalArc(x, y, rx, ry, 0, 2*math.Pi)
	dc.ClosePath()
}

// DrawCircle draws a circle of radius r at position x,y.
func (dc *Context) DrawCircle(x, y, r float64) {
	dc.NewSubPath()
	dc.DrawEllipticalArc(x, y, r, r, 0, 2*math.Pi)
	dc.ClosePath()
}

func (dc *Context) drawRegularPolygon(n int, x, y, r, rotation float64) {
	angle := 2 * math.Pi / float64(n)
	rotation -= math.Pi / 2
	if n%2 == 0 {
		rotation += angle / 2
	}
	dc.NewSubPath()
	for i := 0; i < n; i++ {
		a := rotation + angle*float64(i)
		dc.LineTo(x+r*math.Cos(a), y+r*math.Sin(a))
	}
	dc.ClosePath()
}

// DrawImage draws the specified image at the specified point.
func (dc *Context) DrawImage(im image.Image, x, y int) {
	dc.DrawImageAnchored(im, x, y, 0, 0)
}

// DrawImageAnchored draws the specified image at the specified anchor point.
// The anchor point is x - w * ax, y - h * ay, where w, h is the size of the
// image. Use ax=0.5, ay=0.5 to center the image at the specified point.
func (dc *Context) DrawImageAnchored(im image.Image, x, y int, ax, ay float64) {
	s := im.Bounds().Size()
	x -= int(ax * float64(s.X))
	y -= int(ay * float64(s.Y))
	transformer := draw.BiLinear
	m := dc.matrix.Clone()
	m.Translate(float64(x), float64(y))
	s2d := f64.Aff3{m[0], m[3], m[6], m[1], m[4], m[7]}
	if dc.mask == nil {
		transformer.Transform(dc.im, s2d, im, im.Bounds(), draw.Over, nil)
	} else {
		transformer.Transform(dc.im, s2d, im, im.Bounds(), draw.Over, &draw.Options{
			DstMask:  dc.mask,
			DstMaskP: image.ZP,
		})
	}
}

//
// Text operations
//

// TextState returns the current text state.
func (dc *Context) TextState() *context.TextState {
	return dc.textState
}

func (dc *Context) drawString(im *image.RGBA, s string, x, y float64) {
	d := &font.Drawer{
		Dst:  im,
		Src:  image.NewUniform(dc.color),
		Face: dc.textState.Tf.Face,
		Dot:  fixedPoint(transform.NewPoint(x, y)),
	}
	// based on Drawer.DrawString() in golang.org/x/image/font/font.go
	prevC := rune(-1)
	for _, c := range s {
		if prevC >= 0 {
			d.Dot.X += d.Face.Kern(prevC, c)
		}
		dr, mask, maskp, advance, ok := d.Face.Glyph(d.Dot, c)
		if !ok {
			// TODO: is falling back on the U+FFFD glyph the responsibility of
			// the Drawer or the Face?
			// TODO: set prevC = '\ufffd'?
			continue
		}
		sr := dr.Sub(dr.Min)
		transformer := draw.BiLinear
		m := dc.matrix.Clone()
		m.Translate(float64(dr.Min.X), float64(dr.Min.Y))
		s2d := f64.Aff3{m[0], m[3], m[6], m[1], m[4], m[7]}
		transformer.Transform(d.Dst, s2d, d.Src, sr, draw.Over, &draw.Options{
			SrcMask:  mask,
			SrcMaskP: maskp,
		})
		d.Dot.X += advance
		prevC = c
	}
}

// DrawString draws the specified text at the specified point.
func (dc *Context) DrawString(s string, x, y float64) {
	dc.DrawStringAnchored(s, x, y, 0, 0)
}

// DrawStringAnchored draws the specified text at the specified anchor point.
// The anchor point is x - w * ax, y - h * ay, where w, h is the size of the
// text. Use ax=0.5, ay=0.5 to center the text at the specified point.
func (dc *Context) DrawStringAnchored(s string, x, y, ax, ay float64) {
	w, h := dc.MeasureString(s)
	x -= ax * w
	y += ay * h
	if dc.mask == nil {
		dc.drawString(dc.im, s, x, y)
	} else {
		im := image.NewRGBA(image.Rect(0, 0, dc.width, dc.height))
		dc.drawString(im, s, x, y)
		draw.DrawMask(dc.im, dc.im.Bounds(), im, image.ZP, dc.mask, image.ZP, draw.Over)
	}
}

// MeasureString returns the rendered width and height of the specified text
// given the current font face.
func (dc *Context) MeasureString(s string) (w, h float64) {
	d := &font.Drawer{
		Face: dc.textState.Tf.Face,
	}
	a := d.MeasureString(s)
	return float64(a >> 6), dc.textState.Tf.Size
}

//
// Transformation matrix operations
//

// Matrix returns the current transformation matrix.
func (dc *Context) Matrix() transform.Matrix {
	return dc.matrix
}

// SetMatrix modifies the transformation matrix.
func (dc *Context) SetMatrix(m transform.Matrix) {
	dc.matrix = m
}

// Identity resets the current transformation matrix to the identity matrix.
// This results in no translating, scaling, rotating, or shearing.
func (dc *Context) Identity() {
	dc.matrix = transform.IdentityMatrix()
}

// Translate updates the current matrix with a translation.
func (dc *Context) Translate(x, y float64) {
	dc.matrix.Translate(x, y)
}

// Scale updates the current matrix with a scaling factor.
// Scaling occurs about the origin.
func (dc *Context) Scale(x, y float64) {
	dc.matrix.Scale(x, y)
}

// ScaleAbout updates the current matrix with a scaling factor.
// Scaling occurs about the specified point.
func (dc *Context) ScaleAbout(sx, sy, x, y float64) {
	dc.Translate(x, y)
	dc.Scale(sx, sy)
	dc.Translate(-x, -y)
}

// Rotate updates the current matrix with a anticlockwise rotation.
// Rotation occurs about the origin. Angle is specified in radians.
func (dc *Context) Rotate(angle float64) {
	dc.matrix.Rotate(angle)
}

// RotateAbout updates the current matrix with a anticlockwise rotation.
// Rotation occurs about the specified point. Angle is specified in radians.
func (dc *Context) RotateAbout(angle, x, y float64) {
	dc.Translate(x, y)
	dc.Rotate(angle)
	dc.Translate(-x, -y)
}

// Shear updates the current matrix with a shearing angle.
// Shearing occurs about the origin.
func (dc *Context) Shear(x, y float64) {
	dc.matrix.Shear(x, y)
}

// ShearAbout updates the current matrix with a shearing angle.
// Shearing occurs about the specified point.
func (dc *Context) ShearAbout(sx, sy, x, y float64) {
	dc.Translate(x, y)
	dc.Shear(sx, sy)
	dc.Translate(-x, -y)
}

// Transform multiplies the specified point by the current matrix,
// returning a transformed position.
func (dc *Context) Transform(x, y float64) (tx, ty float64) {
	return dc.matrix.Transform(x, y)
}

//
// Stack operations
//

// Push saves the current state of the context for later retrieval. These
// can be nested.
func (dc *Context) Push() {
	x := *dc
	dc.stack = append(dc.stack, &x)
}

// Pop restores the last saved context state from the stack.
func (dc *Context) Pop() {
	before := *dc
	s := dc.stack
	x, s := s[len(s)-1], s[:len(s)-1]
	*dc = *x
	//dc.mask = before.mask
	dc.strokePath = before.strokePath
	dc.fillPath = before.fillPath
	dc.start = before.start
	dc.current = before.current
	dc.hasCurrent = before.hasCurrent
	dc.textState = before.textState
}