migrated module to git.milar.in

Add conic gradient

README.md

@@ -6,11 +6,16 @@
 
 ## Installation
 
-    go get github.com/fogleman/gg
+    go get -u github.com/fogleman/gg
 
-## GoDoc
+Alternatively, you may use gopkg.in to grab a specific major-version:
 
-https://godoc.org/github.com/fogleman/gg
+    go get -u gopkg.in/fogleman/gg.v1
+
+## Documentation
+
+- godoc: https://godoc.org/github.com/fogleman/gg
+- pkg.go.dev: https://pkg.go.dev/github.com/fogleman/gg?tab=doc
 
 ## Hello, Circle!
 
@@ -91,6 +96,7 @@ DrawString(s string, x, y float64)
 DrawStringAnchored(s string, x, y, ax, ay float64)
 DrawStringWrapped(s string, x, y, ax, ay, width, lineSpacing float64, align Align)
 MeasureString(s string) (w, h float64)
+MeasureMultilineString(s string, lineSpacing float64) (w, h float64)
 WordWrap(s string, w float64) []string
 SetFontFace(fontFace font.Face)
 LoadFontFace(path string, points float64) error
@@ -116,12 +122,13 @@ SetLineWidth(lineWidth float64)
 SetLineCap(lineCap LineCap)
 SetLineJoin(lineJoin LineJoin)
 SetDash(dashes ...float64)
+SetDashOffset(offset float64)
 SetFillRule(fillRule FillRule)
 ```
 
 ## Gradients & Patterns
 
-`gg` supports linear and radial gradients and surface patterns. You can also implement your own patterns.
+`gg` supports linear, radial and conic gradients and surface patterns. You can also implement your own patterns.
 
 ```go
 SetFillStyle(pattern Pattern)
@@ -129,6 +136,7 @@ SetStrokeStyle(pattern Pattern)
 NewSolidPattern(color color.Color)
 NewLinearGradient(x0, y0, x1, y1 float64)
 NewRadialGradient(x0, y0, r0, x1, y1, r1 float64)
+NewConicGradient(cx, cy, deg float64)
 NewSurfacePattern(im image.Image, op RepeatOp)
 ```
 
@@ -151,8 +159,6 @@ It is often desired to rotate or scale about a point that is not the origin. The
 
 `InvertY` is provided in case Y should increase from bottom to top vs. the default top to bottom.
 
-Note: transforms do not currently affect `DrawImage` or `DrawString`.
-
 ## Stack Functions
 
 Save and restore the state of the context. These can be nested.
@@ -171,6 +177,9 @@ defined using paths.
 Clip()
 ClipPreserve()
 ResetClip()
+AsMask() *image.Alpha
+SetMask(mask *image.Alpha)
+InvertMask()
 ```
 
 ## Helper Functions
@@ -187,12 +196,6 @@ SavePNG(path string, im image.Image) error
 
 ![Separator](http://i.imgur.com/fsUvnPB.png)
 
-## How Do it Do?
-
-`gg` is mostly a wrapper around `github.com/golang/freetype/raster`. The goal
-is to provide some more functionality and a nicer API that will suffice for
-most use cases.
-
 ## Another Example
 
 See the output of this example below.

context.go

@@ -2,16 +2,20 @@
 package gg
 
 import (
+	"errors"
 	"image"
 	"image/color"
-	"image/draw"
+	"image/jpeg"
 	"image/png"
 	"io"
 	"math"
+	"strings"
 
 	"github.com/golang/freetype/raster"
+	"golang.org/x/image/draw"
 	"golang.org/x/image/font"
 	"golang.org/x/image/font/basicfont"
+	"golang.org/x/image/math/f64"
 )
 
 type LineCap int
@@ -52,6 +56,7 @@ var (
 type Context struct {
 	width         int
 	height        int
+	rasterizer    *raster.Rasterizer
 	im            *image.RGBA
 	mask          *image.Alpha
 	color         color.Color
@@ -63,6 +68,7 @@ type Context struct {
 	current       Point
 	hasCurrent    bool
 	dashes        []float64
+	dashOffset    float64
 	lineWidth     float64
 	lineCap       LineCap
 	lineJoin      LineJoin
@@ -88,9 +94,12 @@ func NewContextForImage(im image.Image) *Context {
 // 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:         im.Bounds().Size().X,
+		width:         w,
-		height:        im.Bounds().Size().Y,
+		height:        h,
+		rasterizer:    raster.NewRasterizer(w, h),
 		im:            im,
 		color:         color.Transparent,
 		fillPattern:   defaultFillStyle,
@@ -103,6 +112,15 @@ func NewContextForRGBA(im *image.RGBA) *Context {
 	}
 }
 
+// GetCurrentPoint will return the current point and if there is a current point.
+// The point will have been transformed by the context's transformation matrix.
+func (dc *Context) GetCurrentPoint() (Point, bool) {
+	if dc.hasCurrent {
+		return dc.current, true
+	}
+	return Point{}, false
+}
+
 // Image returns the image that has been drawn by this context.
 func (dc *Context) Image() image.Image {
 	return dc.im
@@ -123,11 +141,23 @@ func (dc *Context) SavePNG(path string) error {
 	return SavePNG(path, dc.im)
 }
 
+// SaveJPG encodes the image as a JPG and writes it to disk.
+func (dc *Context) SaveJPG(path string, quality int) error {
+	return SaveJPG(path, dc.im, quality)
+}
+
 // EncodePNG encodes the image as a PNG and writes it to the provided io.Writer.
 func (dc *Context) EncodePNG(w io.Writer) error {
 	return png.Encode(w, dc.im)
 }
 
+// EncodeJPG encodes the image as a JPG and writes it to the provided io.Writer
+// in JPEG 4:2:0 baseline format with the given options.
+// Default parameters are used if a nil *jpeg.Options is passed.
+func (dc *Context) EncodeJPG(w io.Writer, o *jpeg.Options) error {
+	return jpeg.Encode(w, dc.im, o)
+}
+
 // 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.
@@ -135,6 +165,12 @@ 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
+}
+
 func (dc *Context) SetLineWidth(lineWidth float64) {
 	dc.lineWidth = lineWidth
 }
@@ -373,14 +409,16 @@ func (dc *Context) joiner() raster.Joiner {
 func (dc *Context) stroke(painter raster.Painter) {
 	path := dc.strokePath
 	if len(dc.dashes) > 0 {
-		path = dashed(path, dc.dashes)
+		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 := raster.NewRasterizer(dc.width, dc.height)
+	r := dc.rasterizer
 	r.UseNonZeroWinding = true
+	r.Clear()
+	r.Dx, r.Dy = dc.im.Bounds().Min.X, dc.im.Bounds().Min.Y
 	r.AddStroke(path, fix(dc.lineWidth), dc.capper(), dc.joiner())
 	r.Rasterize(painter)
 }
@@ -392,8 +430,10 @@ func (dc *Context) fill(painter raster.Painter) {
 		copy(path, dc.fillPath)
 		path.Add1(dc.start.Fixed())
 	}
-	r := raster.NewRasterizer(dc.width, dc.height)
+	r := dc.rasterizer
 	r.UseNonZeroWinding = dc.fillRule == FillRuleWinding
+	r.Clear()
+	r.Dx, r.Dy = dc.im.Bounds().Min.X, dc.im.Bounds().Min.Y
 	r.AddPath(path)
 	r.Rasterize(painter)
 }
@@ -402,7 +442,19 @@ func (dc *Context) fill(painter raster.Painter) {
 // line cap, line join and dash settings. The path is preserved after this
 // operation.
 func (dc *Context) StrokePreserve() {
-	painter := newPatternPainter(dc.im, dc.mask, dc.strokePattern)
+	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)
 }
 
@@ -417,7 +469,19 @@ func (dc *Context) Stroke() {
 // 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() {
-	painter := newPatternPainter(dc.im, dc.mask, dc.fillPattern)
+	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)
 }
 
@@ -444,6 +508,38 @@ func (dc *Context) ClipPreserve() {
 	}
 }
 
+// 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.
@@ -520,14 +616,18 @@ func (dc *Context) DrawEllipticalArc(x, y, rx, ry, angle1, angle2 float64) {
 		a2 := angle1 + (angle2-angle1)*p2
 		x0 := x + rx*math.Cos(a1)
 		y0 := y + ry*math.Sin(a1)
-		x1 := x + rx*math.Cos(a1+(a2-a1)/2)
+		x1 := x + rx*math.Cos((a1+a2)/2)
-		y1 := y + ry*math.Sin(a1+(a2-a1)/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 && !dc.hasCurrent {
+		if i == 0 {
-			dc.MoveTo(x0, y0)
+			if dc.hasCurrent {
+				dc.LineTo(x0, y0)
+			} else {
+				dc.MoveTo(x0, y0)
+			}
 		}
 		dc.QuadraticTo(cx, cy, x2, y2)
 	}
@@ -564,7 +664,6 @@ func (dc *Context) DrawRegularPolygon(n int, x, y, r, rotation float64) {
 }
 
 // DrawImage draws the specified image at the specified point.
-// Currently, rotation and scaling transforms are not supported.
 func (dc *Context) DrawImage(im image.Image, x, y int) {
 	dc.DrawImageAnchored(im, x, y, 0, 0)
 }
@@ -576,12 +675,17 @@ 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))
-	p := image.Pt(x, y)
+	transformer := draw.BiLinear
-	r := image.Rectangle{p, p.Add(s)}
+	fx, fy := float64(x), float64(y)
+	m := dc.matrix.Translate(fx, fy)
+	s2d := f64.Aff3{m.XX, m.XY, m.X0, m.YX, m.YY, m.Y0}
 	if dc.mask == nil {
-		draw.Draw(dc.im, r, im, image.ZP, draw.Over)
+		transformer.Transform(dc.im, s2d, im, im.Bounds(), draw.Over, nil)
 	} else {
-		draw.DrawMask(dc.im, r, im, image.ZP, dc.mask, p, draw.Over)
+		transformer.Transform(dc.im, s2d, im, im.Bounds(), draw.Over, &draw.Options{
+			DstMask:  dc.mask,
+			DstMaskP: image.ZP,
+		})
 	}
 }
 
@@ -601,6 +705,10 @@ func (dc *Context) LoadFontFace(path string, points float64) error {
 	return err
 }
 
+func (dc *Context) FontHeight() float64 {
+	return dc.fontHeight
+}
+
 func (dc *Context) drawString(im *image.RGBA, s string, x, y float64) {
 	d := &font.Drawer{
 		Dst:  im,
@@ -608,11 +716,34 @@ func (dc *Context) drawString(im *image.RGBA, s string, x, y float64) {
 		Face: dc.fontFace,
 		Dot:  fixp(x, y),
 	}
-	d.DrawString(s)
+	// 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
+		fx, fy := float64(dr.Min.X), float64(dr.Min.Y)
+		m := dc.matrix.Translate(fx, fy)
+		s2d := f64.Aff3{m.XX, m.XY, m.X0, m.YX, m.YY, m.Y0}
+		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.
-// Currently, rotation and scaling transforms are not supported.
 func (dc *Context) DrawString(s string, x, y float64) {
 	dc.DrawStringAnchored(s, x, y, 0, 0)
 }
@@ -622,11 +753,10 @@ func (dc *Context) DrawString(s string, x, y float64) {
 // 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, y = dc.TransformPoint(x, y)
 	x -= ax * w
 	y += ay * h
 	if dc.mask == nil {
-		dc.drawString(dc.im, s, x, y)
+		dc.drawString(dc.im, s, x+float64(dc.im.Bounds().Min.X), y+float64(dc.im.Bounds().Min.Y))
 	} else {
 		im := image.NewRGBA(image.Rect(0, 0, dc.width, dc.height))
 		dc.drawString(im, s, x, y)
@@ -639,8 +769,11 @@ func (dc *Context) DrawStringAnchored(s string, x, y, ax, ay float64) {
 // spacing and text alignment.
 func (dc *Context) DrawStringWrapped(s string, x, y, ax, ay, width, lineSpacing float64, align Align) {
 	lines := dc.WordWrap(s, width)
+
+	// sync h formula with MeasureMultilineString
 	h := float64(len(lines)) * dc.fontHeight * lineSpacing
 	h -= (lineSpacing - 1) * dc.fontHeight
+
 	x -= ax * width
 	y -= ay * h
 	switch align {
@@ -660,6 +793,29 @@ func (dc *Context) DrawStringWrapped(s string, x, y, ax, ay, width, lineSpacing
 	}
 }
 
+func (dc *Context) MeasureMultilineString(s string, lineSpacing float64) (width, height float64) {
+	lines := strings.Split(s, "\n")
+
+	// sync h formula with DrawStringWrapped
+	height = float64(len(lines)) * dc.fontHeight * lineSpacing
+	height -= (lineSpacing - 1) * dc.fontHeight
+
+	d := &font.Drawer{
+		Face: dc.fontFace,
+	}
+
+	// max width from lines
+	for _, line := range lines {
+		adv := d.MeasureString(line)
+		currentWidth := float64(adv >> 6) // from gg.Context.MeasureString
+		if currentWidth > width {
+			width = currentWidth
+		}
+	}
+
+	return width, height
+}
+
 // 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) {
@@ -703,13 +859,13 @@ func (dc *Context) ScaleAbout(sx, sy, x, y float64) {
 	dc.Translate(-x, -y)
 }
 
-// Rotate updates the current matrix with a clockwise rotation.
+// 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 = dc.matrix.Rotate(angle)
 }
 
-// RotateAbout updates the current matrix with a clockwise rotation.
+// 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)

context_test.go

@@ -0,0 +1,323 @@
+package gg
+
+import (
+	"crypto/md5"
+	"flag"
+	"fmt"
+	"image/color"
+	"math/rand"
+	"testing"
+)
+
+var save bool
+
+func init() {
+	flag.BoolVar(&save, "save", false, "save PNG output for each test case")
+	flag.Parse()
+}
+
+func hash(dc *Context) string {
+	return fmt.Sprintf("%x", md5.Sum(dc.im.Pix))
+}
+
+func checkHash(t *testing.T, dc *Context, expected string) {
+	actual := hash(dc)
+	if actual != expected {
+		t.Fatalf("expected hash: %s != actual hash: %s", expected, actual)
+	}
+}
+
+func saveImage(dc *Context, name string) error {
+	if save {
+		return SavePNG(name+".png", dc.Image())
+	}
+	return nil
+}
+
+func TestBlank(t *testing.T) {
+	dc := NewContext(100, 100)
+	saveImage(dc, "TestBlank")
+	checkHash(t, dc, "4e0a293a5b638f0aba2c4fe2c3418d0e")
+}
+
+func TestGrid(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	for i := 10; i < 100; i += 10 {
+		x := float64(i) + 0.5
+		dc.DrawLine(x, 0, x, 100)
+		dc.DrawLine(0, x, 100, x)
+	}
+	dc.SetRGB(0, 0, 0)
+	dc.Stroke()
+	saveImage(dc, "TestGrid")
+	checkHash(t, dc, "78606adda71d8abfbd8bb271087e4d69")
+}
+
+func TestLines(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(0.5, 0.5, 0.5)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 100; i++ {
+		x1 := rnd.Float64() * 100
+		y1 := rnd.Float64() * 100
+		x2 := rnd.Float64() * 100
+		y2 := rnd.Float64() * 100
+		dc.DrawLine(x1, y1, x2, y2)
+		dc.SetLineWidth(rnd.Float64() * 3)
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Stroke()
+	}
+	saveImage(dc, "TestLines")
+	checkHash(t, dc, "036bd220e2529955cc48425dd72bb686")
+}
+
+func TestCircles(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 10; i++ {
+		x := rnd.Float64() * 100
+		y := rnd.Float64() * 100
+		r := rnd.Float64()*10 + 5
+		dc.DrawCircle(x, y, r)
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.FillPreserve()
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.SetLineWidth(rnd.Float64() * 3)
+		dc.Stroke()
+	}
+	saveImage(dc, "TestCircles")
+	checkHash(t, dc, "c52698000df96fabafe7863701afe922")
+}
+
+func TestQuadratic(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(0.25, 0.25, 0.25)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 100; i++ {
+		x1 := rnd.Float64() * 100
+		y1 := rnd.Float64() * 100
+		x2 := rnd.Float64() * 100
+		y2 := rnd.Float64() * 100
+		x3 := rnd.Float64() * 100
+		y3 := rnd.Float64() * 100
+		dc.MoveTo(x1, y1)
+		dc.QuadraticTo(x2, y2, x3, y3)
+		dc.SetLineWidth(rnd.Float64() * 3)
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Stroke()
+	}
+	saveImage(dc, "TestQuadratic")
+	checkHash(t, dc, "56b842d814aee94b52495addae764a77")
+}
+
+func TestCubic(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(0.75, 0.75, 0.75)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 100; i++ {
+		x1 := rnd.Float64() * 100
+		y1 := rnd.Float64() * 100
+		x2 := rnd.Float64() * 100
+		y2 := rnd.Float64() * 100
+		x3 := rnd.Float64() * 100
+		y3 := rnd.Float64() * 100
+		x4 := rnd.Float64() * 100
+		y4 := rnd.Float64() * 100
+		dc.MoveTo(x1, y1)
+		dc.CubicTo(x2, y2, x3, y3, x4, y4)
+		dc.SetLineWidth(rnd.Float64() * 3)
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Stroke()
+	}
+	saveImage(dc, "TestCubic")
+	checkHash(t, dc, "4a7960fc4eaaa33ce74131c5ce0afca8")
+}
+
+func TestFill(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 10; i++ {
+		dc.NewSubPath()
+		for j := 0; j < 10; j++ {
+			x := rnd.Float64() * 100
+			y := rnd.Float64() * 100
+			dc.LineTo(x, y)
+		}
+		dc.ClosePath()
+		dc.SetRGBA(rnd.Float64(), rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Fill()
+	}
+	saveImage(dc, "TestFill")
+	checkHash(t, dc, "7ccb3a2443906a825e57ab94db785467")
+}
+
+func TestClip(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	dc.DrawCircle(50, 50, 40)
+	dc.Clip()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 1000; i++ {
+		x := rnd.Float64() * 100
+		y := rnd.Float64() * 100
+		r := rnd.Float64()*10 + 5
+		dc.DrawCircle(x, y, r)
+		dc.SetRGBA(rnd.Float64(), rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Fill()
+	}
+	saveImage(dc, "TestClip")
+	checkHash(t, dc, "762c32374d529fd45ffa038b05be7865")
+}
+
+func TestPushPop(t *testing.T) {
+	const S = 100
+	dc := NewContext(S, S)
+	dc.SetRGBA(0, 0, 0, 0.1)
+	for i := 0; i < 360; i += 15 {
+		dc.Push()
+		dc.RotateAbout(Radians(float64(i)), S/2, S/2)
+		dc.DrawEllipse(S/2, S/2, S*7/16, S/8)
+		dc.Fill()
+		dc.Pop()
+	}
+	saveImage(dc, "TestPushPop")
+	checkHash(t, dc, "31e908ee1c2ea180da98fd5681a89d05")
+}
+
+func TestDrawStringWrapped(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	dc.SetRGB(0, 0, 0)
+	dc.DrawStringWrapped("Hello, world! How are you?", 50, 50, 0.5, 0.5, 90, 1.5, AlignCenter)
+	saveImage(dc, "TestDrawStringWrapped")
+	checkHash(t, dc, "8d92f6aae9e8b38563f171abd00893f8")
+}
+
+func TestDrawImage(t *testing.T) {
+	src := NewContext(100, 100)
+	src.SetRGB(1, 1, 1)
+	src.Clear()
+	for i := 10; i < 100; i += 10 {
+		x := float64(i) + 0.5
+		src.DrawLine(x, 0, x, 100)
+		src.DrawLine(0, x, 100, x)
+	}
+	src.SetRGB(0, 0, 0)
+	src.Stroke()
+
+	dc := NewContext(200, 200)
+	dc.SetRGB(0, 0, 0)
+	dc.Clear()
+	dc.DrawImage(src.Image(), 50, 50)
+	saveImage(dc, "TestDrawImage")
+	checkHash(t, dc, "282afbc134676722960b6bec21305b15")
+}
+
+func TestSetPixel(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(0, 0, 0)
+	dc.Clear()
+	dc.SetRGB(0, 1, 0)
+	i := 0
+	for y := 0; y < 100; y++ {
+		for x := 0; x < 100; x++ {
+			if i%31 == 0 {
+				dc.SetPixel(x, y)
+			}
+			i++
+		}
+	}
+	saveImage(dc, "TestSetPixel")
+	checkHash(t, dc, "27dda6b4b1d94f061018825b11982793")
+}
+
+func TestDrawPoint(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(0, 0, 0)
+	dc.Clear()
+	dc.SetRGB(0, 1, 0)
+	dc.Scale(10, 10)
+	for y := 0; y <= 10; y++ {
+		for x := 0; x <= 10; x++ {
+			dc.DrawPoint(float64(x), float64(y), 3)
+			dc.Fill()
+		}
+	}
+	saveImage(dc, "TestDrawPoint")
+	checkHash(t, dc, "55af8874531947ea6eeb62222fb33e0e")
+}
+
+func TestLinearGradient(t *testing.T) {
+	dc := NewContext(100, 100)
+	g := NewLinearGradient(0, 0, 100, 100)
+	g.AddColorStop(0, color.RGBA{0, 255, 0, 255})
+	g.AddColorStop(1, color.RGBA{0, 0, 255, 255})
+	g.AddColorStop(0.5, color.RGBA{255, 0, 0, 255})
+	dc.SetFillStyle(g)
+	dc.DrawRectangle(0, 0, 100, 100)
+	dc.Fill()
+	saveImage(dc, "TestLinearGradient")
+	checkHash(t, dc, "75eb9385c1219b1d5bb6f4c961802c7a")
+}
+
+func TestRadialGradient(t *testing.T) {
+	dc := NewContext(100, 100)
+	g := NewRadialGradient(30, 50, 0, 70, 50, 50)
+	g.AddColorStop(0, color.RGBA{0, 255, 0, 255})
+	g.AddColorStop(1, color.RGBA{0, 0, 255, 255})
+	g.AddColorStop(0.5, color.RGBA{255, 0, 0, 255})
+	dc.SetFillStyle(g)
+	dc.DrawRectangle(0, 0, 100, 100)
+	dc.Fill()
+	saveImage(dc, "TestRadialGradient")
+	checkHash(t, dc, "f170f39c3f35c29de11e00428532489d")
+}
+
+func TestDashes(t *testing.T) {
+	dc := NewContext(100, 100)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < 100; i++ {
+		x1 := rnd.Float64() * 100
+		y1 := rnd.Float64() * 100
+		x2 := rnd.Float64() * 100
+		y2 := rnd.Float64() * 100
+		dc.SetDash(rnd.Float64()*3+1, rnd.Float64()*3+3)
+		dc.DrawLine(x1, y1, x2, y2)
+		dc.SetLineWidth(rnd.Float64() * 3)
+		dc.SetRGB(rnd.Float64(), rnd.Float64(), rnd.Float64())
+		dc.Stroke()
+	}
+	saveImage(dc, "TestDashes")
+	checkHash(t, dc, "d188069c69dcc3970edfac80f552b53c")
+}
+
+func BenchmarkCircles(b *testing.B) {
+	dc := NewContext(1000, 1000)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	rnd := rand.New(rand.NewSource(99))
+	for i := 0; i < b.N; i++ {
+		x := rnd.Float64() * 1000
+		y := rnd.Float64() * 1000
+		dc.DrawCircle(x, y, 10)
+		if i%2 == 0 {
+			dc.SetRGB(0, 0, 0)
+		} else {
+			dc.SetRGB(1, 1, 1)
+		}
+		dc.Fill()
+	}
+}

examples/concat.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"math"
+
+	"github.com/fogleman/gg"
+)
+
+func main() {
+	im1, err := gg.LoadPNG("examples/baboon.png")
+	if err != nil {
+		panic(err)
+	}
+
+	im2, err := gg.LoadPNG("examples/gopher.png")
+	if err != nil {
+		panic(err)
+	}
+
+	s1 := im1.Bounds().Size()
+	s2 := im2.Bounds().Size()
+
+	width := int(math.Max(float64(s1.X), float64(s2.X)))
+	height := s1.Y + s2.Y
+
+	dc := gg.NewContext(width, height)
+	dc.DrawImage(im1, 0, 0)
+	dc.DrawImage(im2, 0, s1.Y)
+	dc.SavePNG("out.png")
+}

examples/crisp.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"github.com/fogleman/gg"
+)
+
+func main() {
+	const W = 1000
+	const H = 1000
+	const Minor = 10
+	const Major = 100
+
+	dc := gg.NewContext(W, H)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+
+	// minor grid
+	for x := Minor; x < W; x += Minor {
+		fx := float64(x) + 0.5
+		dc.DrawLine(fx, 0, fx, H)
+	}
+	for y := Minor; y < H; y += Minor {
+		fy := float64(y) + 0.5
+		dc.DrawLine(0, fy, W, fy)
+	}
+	dc.SetLineWidth(1)
+	dc.SetRGBA(0, 0, 0, 0.25)
+	dc.Stroke()
+
+	// major grid
+	for x := Major; x < W; x += Major {
+		fx := float64(x) + 0.5
+		dc.DrawLine(fx, 0, fx, H)
+	}
+	for y := Major; y < H; y += Major {
+		fy := float64(y) + 0.5
+		dc.DrawLine(0, fy, W, fy)
+	}
+	dc.SetLineWidth(1)
+	dc.SetRGBA(0, 0, 0, 0.5)
+	dc.Stroke()
+
+	dc.SavePNG("out.png")
+}

examples/gofont.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"log"
+
+	"github.com/fogleman/gg"
+	"github.com/golang/freetype/truetype"
+	"golang.org/x/image/font/gofont/goregular"
+)
+
+func main() {
+	font, err := truetype.Parse(goregular.TTF)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	face := truetype.NewFace(font, &truetype.Options{Size: 48})
+
+	dc := gg.NewContext(1024, 1024)
+	dc.SetFontFace(face)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	dc.SetRGB(0, 0, 0)
+	dc.DrawStringAnchored("Hello, world!", 512, 512, 0.5, 0.5)
+	dc.SavePNG("out.png")
+}

examples/gradient-conic.go

@@ -0,0 +1,38 @@
+// +build ignore
+
+package main
+
+import (
+	"image/color"
+
+	"github.com/fogleman/gg"
+)
+
+func main() {
+	dc := gg.NewContext(400, 400)
+
+	grad1 := gg.NewConicGradient(200, 200, 0)
+	grad1.AddColorStop(0.0, color.Black)
+	grad1.AddColorStop(0.5, color.RGBA{255, 215, 0, 255})
+	grad1.AddColorStop(1.0, color.RGBA{255, 0, 0, 255})
+
+	grad2 := gg.NewConicGradient(200, 200, 90)
+	grad2.AddColorStop(0.00, color.RGBA{255, 0, 0, 255})
+	grad2.AddColorStop(0.16, color.RGBA{255, 255, 0, 255})
+	grad2.AddColorStop(0.33, color.RGBA{0, 255, 0, 255})
+	grad2.AddColorStop(0.50, color.RGBA{0, 255, 255, 255})
+	grad2.AddColorStop(0.66, color.RGBA{0, 0, 255, 255})
+	grad2.AddColorStop(0.83, color.RGBA{255, 0, 255, 255})
+	grad2.AddColorStop(1.00, color.RGBA{255, 0, 0, 255})
+
+	dc.SetStrokeStyle(grad1)
+	dc.SetLineWidth(20)
+	dc.DrawCircle(200, 200, 180)
+	dc.Stroke()
+
+	dc.SetFillStyle(grad2)
+	dc.DrawCircle(200, 200, 150)
+	dc.Fill()
+
+	dc.SavePNG("gradient-conic.png")
+}

examples/gradient-text.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"image/color"
+
+	"github.com/fogleman/gg"
+)
+
+const (
+	W = 1024
+	H = 512
+)
+
+func main() {
+	dc := gg.NewContext(W, H)
+
+	// draw text
+	dc.SetRGB(0, 0, 0)
+	dc.LoadFontFace("/Library/Fonts/Impact.ttf", 128)
+	dc.DrawStringAnchored("Gradient Text", W/2, H/2, 0.5, 0.5)
+
+	// get the context as an alpha mask
+	mask := dc.AsMask()
+
+	// clear the context
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+
+	// set a gradient
+	g := gg.NewLinearGradient(0, 0, W, H)
+	g.AddColorStop(0, color.RGBA{255, 0, 0, 255})
+	g.AddColorStop(1, color.RGBA{0, 0, 255, 255})
+	dc.SetFillStyle(g)
+
+	// using the mask, fill the context with the gradient
+	dc.SetMask(mask)
+	dc.DrawRectangle(0, 0, W, H)
+	dc.Fill()
+
+	dc.SavePNG("out.png")
+}

examples/invert-mask.go

@@ -0,0 +1,14 @@
+package main
+
+import "github.com/fogleman/gg"
+
+func main() {
+	dc := gg.NewContext(1024, 1024)
+	dc.DrawCircle(512, 512, 384)
+	dc.Clip()
+	dc.InvertMask()
+	dc.DrawRectangle(0, 0, 1024, 1024)
+	dc.SetRGB(0, 0, 0)
+	dc.Fill()
+	dc.SavePNG("out.png")
+}

examples/mask.go

@@ -7,7 +7,7 @@ import (
 )
 
 func main() {
-	im, err := gg.LoadImage("examples/lenna.png")
+	im, err := gg.LoadImage("examples/baboon.png")
 	if err != nil {
 		log.Fatal(err)
 	}

examples/pattern-fill.go

@@ -3,7 +3,7 @@ package main
 import "github.com/fogleman/gg"
 
 func main() {
-	im, err := gg.LoadPNG("examples/lenna.png")
+	im, err := gg.LoadPNG("examples/baboon.png")
 	if err != nil {
 		panic(err)
 	}

examples/rotated-image.go

@@ -0,0 +1,34 @@
+package main
+
+import "github.com/fogleman/gg"
+
+func main() {
+	const W = 400
+	const H = 500
+	im, err := gg.LoadPNG("examples/gopher.png")
+	if err != nil {
+		panic(err)
+	}
+	iw, ih := im.Bounds().Dx(), im.Bounds().Dy()
+	dc := gg.NewContext(W, H)
+	// draw outline
+	dc.SetHexColor("#ff0000")
+	dc.SetLineWidth(1)
+	dc.DrawRectangle(0, 0, float64(W), float64(H))
+	dc.Stroke()
+	// draw full image
+	dc.SetHexColor("#0000ff")
+	dc.SetLineWidth(2)
+	dc.DrawRectangle(100, 210, float64(iw), float64(ih))
+	dc.Stroke()
+	dc.DrawImage(im, 100, 210)
+	// draw image with current matrix applied
+	dc.SetHexColor("#0000ff")
+	dc.SetLineWidth(2)
+	dc.Rotate(gg.Radians(10))
+	dc.DrawRectangle(100, 0, float64(iw), float64(ih)/2+20.0)
+	dc.StrokePreserve()
+	dc.Clip()
+	dc.DrawImageAnchored(im, 100, 0, 0.0, 0.0)
+	dc.SavePNG("out.png")
+}

examples/rotated-text.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"github.com/fogleman/gg"
+	"github.com/golang/freetype/truetype"
+	"golang.org/x/image/font/gofont/goregular"
+)
+
+func main() {
+	const S = 400
+	dc := gg.NewContext(S, S)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	dc.SetRGB(0, 0, 0)
+	font, err := truetype.Parse(goregular.TTF)
+	if err != nil {
+		panic("")
+	}
+	face := truetype.NewFace(font, &truetype.Options{
+		Size: 40,
+	})
+	dc.SetFontFace(face)
+	text := "Hello, world!"
+	w, h := dc.MeasureString(text)
+	dc.Rotate(gg.Radians(10))
+	dc.DrawRectangle(100, 180, w, h)
+	dc.Stroke()
+	dc.DrawStringAnchored(text, 100, 180, 0.0, 0.0)
+	dc.SavePNG("out.png")
+}

examples/unicode.go

@@ -0,0 +1,25 @@
+package main
+
+import "github.com/fogleman/gg"
+
+func main() {
+	const S = 4096 * 2
+	const T = 16 * 2
+	const F = 28
+	dc := gg.NewContext(S, S)
+	dc.SetRGB(1, 1, 1)
+	dc.Clear()
+	dc.SetRGB(0, 0, 0)
+	if err := dc.LoadFontFace("Xolonium-Regular.ttf", F); err != nil {
+		panic(err)
+	}
+	for r := 0; r < 256; r++ {
+		for c := 0; c < 256; c++ {
+			i := r*256 + c
+			x := float64(c*T) + T/2
+			y := float64(r*T) + T/2
+			dc.DrawStringAnchored(string(rune(i)), x, y, 0.5, 0.5)
+		}
+	}
+	dc.SavePNG("out.png")
+}

go.mod

@@ -0,0 +1,9 @@
+module git.milar.in/milarin/gg
+
+go 1.18
+
+require (
+	github.com/fogleman/gg v1.3.0
+	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0
+	golang.org/x/image v0.0.0-20220413100746-70e8d0d3baa9
+)

go.sum

@@ -0,0 +1,8 @@
+github.com/fogleman/gg v1.3.0 h1:/7zJX8F6AaYQc57WQCyN9cAIz+4bCJGO9B+dyW29am8=
+github.com/fogleman/gg v1.3.0/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
+github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
+github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0/go.mod h1:E/TSTwGwJL78qG/PmXZO1EjYhfJinVAhrmmHX6Z8B9k=
+golang.org/x/image v0.0.0-20220413100746-70e8d0d3baa9 h1:LRtI4W37N+KFebI/qV0OFiLUv4GLOWeEW5hn/KEJvxE=
+golang.org/x/image v0.0.0-20220413100746-70e8d0d3baa9/go.mod h1:023OzeP/+EPmXeapQh35lcL3II3LrY8Ic+EFFKVhULM=
+golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=

gradient.go

@@ -164,6 +164,52 @@ func NewRadialGradient(x0, y0, r0, x1, y1, r1 float64) Gradient {
 	return g
 }
 
+// Conic Gradient
+type conicGradient struct {
+	cx, cy   float64
+	rotation float64
+	stops    stops
+}
+
+func (g *conicGradient) ColorAt(x, y int) color.Color {
+	if len(g.stops) == 0 {
+		return color.Transparent
+	}
+	a := math.Atan2(float64(y)-g.cy, float64(x)-g.cx)
+	t := norm(a, -math.Pi, math.Pi) - g.rotation
+	if t < 0 {
+		t += 1
+	}
+	return getColor(t, g.stops)
+}
+
+func (g *conicGradient) AddColorStop(offset float64, color color.Color) {
+	g.stops = append(g.stops, stop{pos: offset, color: color})
+	sort.Sort(g.stops)
+}
+
+func NewConicGradient(cx, cy, deg float64) Gradient {
+	g := &conicGradient{
+		cx:       cx,
+		cy:       cy,
+		rotation: normalizeAngle(deg) / 360,
+	}
+	return g
+}
+
+func normalizeAngle(t float64) float64 {
+	t = math.Mod(t, 360)
+	if t < 0 {
+		t += 360
+	}
+	return t
+}
+
+// Map value which is in range [a..b] to range [0..1]
+func norm(value, a, b float64) float64 {
+	return (value - a) * (1.0 / (b - a))
+}
+
 func getColor(pos float64, stops stops) color.Color {
 	if pos <= 0.0 || len(stops) == 1 {
 		return stops[0].color
@@ -189,7 +235,7 @@ func colorLerp(c0, c1 color.Color, t float64) color.Color {
 	r0, g0, b0, a0 := c0.RGBA()
 	r1, g1, b1, a1 := c1.RGBA()
 
-	return color.NRGBA{
+	return color.RGBA{
 		lerp(r0, r1, t),
 		lerp(g0, g1, t),
 		lerp(b0, b1, t),

path.go

@@ -1,6 +1,8 @@
 package gg
 
 import (
+	"math"
+
 	"github.com/golang/freetype/raster"
 	"golang.org/x/image/math/fixed"
 )
@@ -57,7 +59,7 @@ func flattenPath(p raster.Path) [][]Point {
 	return result
 }
 
-func dashPath(paths [][]Point, dashes []float64) [][]Point {
+func dashPath(paths [][]Point, dashes []float64, offset float64) [][]Point {
 	var result [][]Point
 	if len(dashes) == 0 {
 		return paths
@@ -73,6 +75,27 @@ func dashPath(paths [][]Point, dashes []float64) [][]Point {
 		pathIndex := 1
 		dashIndex := 0
 		segmentLength := 0.0
+
+		// offset
+		if offset != 0 {
+			var totalLength float64
+			for _, dashLength := range dashes {
+				totalLength += dashLength
+			}
+			offset = math.Mod(offset, totalLength)
+			if offset < 0 {
+				offset += totalLength
+			}
+			for i, dashLength := range dashes {
+				offset -= dashLength
+				if offset < 0 {
+					dashIndex = i
+					segmentLength = dashLength + offset
+					break
+				}
+			}
+		}
+
 		var segment []Point
 		segment = append(segment, previous)
 		for pathIndex < len(path) {
@@ -135,6 +158,6 @@ func rasterPath(paths [][]Point) raster.Path {
 	return result
 }
 
-func dashed(path raster.Path, dashes []float64) raster.Path {
+func dashed(path raster.Path, dashes []float64, offset float64) raster.Path {
-	return rasterPath(dashPath(flattenPath(path), dashes))
+	return rasterPath(dashPath(flattenPath(path), dashes, offset))
 }

util.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"image"
 	"image/draw"
+	"image/jpeg"
 	_ "image/jpeg"
 	"image/png"
 	"io/ioutil"
@@ -53,9 +54,32 @@ func SavePNG(path string, im image.Image) error {
 	return png.Encode(file, im)
 }
 
+func LoadJPG(path string) (image.Image, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+	return jpeg.Decode(file)
+}
+
+func SaveJPG(path string, im image.Image, quality int) error {
+	file, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	var opt jpeg.Options
+	opt.Quality = quality
+
+	return jpeg.Encode(file, im, &opt)
+}
+
 func imageToRGBA(src image.Image) *image.RGBA {
-	dst := image.NewRGBA(src.Bounds())
+	bounds := src.Bounds()
-	draw.Draw(dst, dst.Rect, src, image.ZP, draw.Src)
+	dst := image.NewRGBA(bounds)
+	draw.Draw(dst, bounds, src, bounds.Min, draw.Src)
 	return dst
 }
 
@@ -85,7 +109,7 @@ func fixp(x, y float64) fixed.Point26_6 {
 }
 
 func fix(x float64) fixed.Int26_6 {
-	return fixed.Int26_6(x * 64)
+	return fixed.Int26_6(math.Round(x * 64))
 }
 
 func unfix(x fixed.Int26_6) float64 {
@@ -100,6 +124,11 @@ func unfix(x fixed.Int26_6) float64 {
 	return 0
 }
 
+// LoadFontFace is a helper function to load the specified font file with
+// the specified point size. Note that the returned `font.Face` objects
+// are not thread safe and cannot be used in parallel across goroutines.
+// You can usually just use the Context.LoadFontFace function instead of
+// this package-level function.
 func LoadFontFace(path string, points float64) (font.Face, error) {
 	fontBytes, err := ioutil.ReadFile(path)
 	if err != nil {