initial commit

context.go

@@ -0,0 +1,157 @@
+package dd
+
+import (
+	"image"
+	"image/color"
+	"image/draw"
+
+	"github.com/golang/freetype/raster"
+	"golang.org/x/image/math/fixed"
+)
+
+type LineCap int
+
+const (
+	LineCapRound LineCap = iota
+	LineCapButt
+	LineCapSquare
+)
+
+type LineJoin int
+
+const (
+	LineJoinRound LineJoin = iota
+	LineJoinBevel
+)
+
+type Context struct {
+	width     int
+	height    int
+	im        *image.RGBA
+	color     color.Color
+	path      raster.Path
+	start     fixed.Point26_6
+	lineWidth float64
+	capper    raster.Capper
+	joiner    raster.Joiner
+}
+
+func NewContext(width, height int) *Context {
+	im := image.NewRGBA(image.Rect(0, 0, width, height))
+	return &Context{
+		width:     width,
+		height:    height,
+		im:        im,
+		color:     color.Transparent,
+		lineWidth: 1,
+	}
+}
+
+func (c *Context) Image() image.Image {
+	return c.im
+}
+
+func (c *Context) Width() int {
+	return c.width
+}
+
+func (c *Context) Height() int {
+	return c.height
+}
+
+func (c *Context) WriteToPNG(path string) error {
+	return writeToPNG(path, c.im)
+}
+
+func (c *Context) Paint() {
+	draw.Draw(c.im, c.im.Bounds(), image.NewUniform(c.color), image.ZP, draw.Src)
+}
+
+func (c *Context) SetSourceRGBA(r, g, b, a float64) {
+	c.color = color.RGBA{
+		uint8(r * 255),
+		uint8(g * 255),
+		uint8(b * 255),
+		uint8(a * 255),
+	}
+}
+
+func (c *Context) SetSourceRGB(r, g, b float64) {
+	c.SetSourceRGBA(r, g, b, 1)
+}
+
+func (c *Context) SetLineWidth(lineWidth float64) {
+	c.lineWidth = lineWidth
+}
+
+func (c *Context) SetLineCap(lineCap LineCap) {
+	switch lineCap {
+	case LineCapButt:
+		c.capper = raster.ButtCapper
+	case LineCapRound:
+		c.capper = raster.RoundCapper
+	case LineCapSquare:
+		c.capper = raster.SquareCapper
+	}
+}
+
+func (c *Context) SetLineJoin(lineJoin LineJoin) {
+	switch lineJoin {
+	case LineJoinBevel:
+		c.joiner = raster.BevelJoiner
+	case LineJoinRound:
+		c.joiner = raster.RoundJoiner
+	}
+}
+
+func (c *Context) MoveTo(x, y float64) {
+	c.start = fp(x, y)
+	c.path.Start(c.start)
+}
+
+func (c *Context) LineTo(x, y float64) {
+	c.path.Add1(fp(x, y))
+}
+
+func (c *Context) QuadraticTo(x1, y1, x2, y2 float64) {
+	c.path.Add2(fp(x1, y1), fp(x2, y2))
+}
+
+func (c *Context) ClosePath() {
+	c.path.Add1(c.start)
+}
+
+func (c *Context) NewPath() {
+	c.path.Clear()
+}
+
+func (c *Context) StrokePreserve() {
+	painter := raster.NewRGBAPainter(c.im)
+	painter.SetColor(c.color)
+	r := raster.NewRasterizer(c.width, c.height)
+	r.UseNonZeroWinding = true
+	r.AddStroke(c.path, fi(c.lineWidth), c.capper, c.joiner)
+	r.Rasterize(painter)
+}
+
+func (c *Context) Stroke() {
+	c.StrokePreserve()
+	c.NewPath()
+}
+
+func (c *Context) FillPreserve() {
+	// make sure the path is closed
+	path := make(raster.Path, len(c.path))
+	copy(path, c.path)
+	path.Add1(c.start)
+	painter := raster.NewRGBAPainter(c.im)
+	painter.SetColor(c.color)
+	r := raster.NewRasterizer(c.width, c.height)
+	r.AddPath(path)
+	r.Rasterize(painter)
+}
+
+func (c *Context) Fill() {
+	c.FillPreserve()
+	c.NewPath()
+}

examples/example0.go

@@ -0,0 +1,22 @@
+package main
+
+import "github.com/fogleman/dd"
+
+func main() {
+	dc := dd.NewContext(256, 256)
+	dc.SetSourceRGBA(1, 0, 0, 0.3)
+	dc.Paint()
+	dc.MoveTo(20, 20)
+	dc.LineTo(236, 236)
+	dc.LineTo(236, 128)
+	dc.LineTo(20, 128)
+	dc.QuadraticTo(0, 64, 120, 20)
+	dc.SetSourceRGBA(1, 0, 0, 0.8)
+	dc.FillPreserve()
+	dc.SetSourceRGB(0, 0, 0)
+	dc.SetLineWidth(8)
+	// dc.SetLineCap(dd.LineCapButt)
+	// dc.SetLineJoin(dd.LineJoinBevel)
+	dc.Stroke()
+	dc.WriteToPNG("out.png")
+}

util.go

@@ -0,0 +1,26 @@
+package dd
+
+import (
+	"image"
+	"image/png"
+	"os"
+
+	"golang.org/x/image/math/fixed"
+)
+
+func writeToPNG(path string, im image.Image) error {
+	file, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	return png.Encode(file, im)
+}
+
+func fp(x, y float64) fixed.Point26_6 {
+	return fixed.Point26_6{fixed.Int26_6(x * 64), fixed.Int26_6(y * 64)}
+}
+
+func fi(x float64) fixed.Int26_6 {
+	return fixed.Int26_6(x * 64)
+}