// rasterize returns the glyph mask and integer-pixel offset to render the
// given glyph at the given sub-pixel offsets.
// The 24.8 fixed point arguments fx and fy must be in the range [0, 1).
func (c *Context) rasterize(glyph truetype.Index, fx, fy raster.Fix32) (*image.Alpha, image.Point, error) {
if err := c.glyphBuf.Load(c.font, glyph); err != nil {
return nil, image.ZP, err
}
// Calculate the integer-pixel bounds for the glyph.
xmin := int(fx+c.FUnitToFix32(+int(c.glyphBuf.B.XMin))) >> 8
ymin := int(fy+c.FUnitToFix32(-int(c.glyphBuf.B.YMax))) >> 8
xmax := int(fx+c.FUnitToFix32(+int(c.glyphBuf.B.XMax))+0xff) >> 8
ymax := int(fy+c.FUnitToFix32(-int(c.glyphBuf.B.YMin))+0xff) >> 8
if xmin > xmax || ymin > ymax {
return nil, image.ZP, errors.New("freetype: negative sized glyph")
}
// A TrueType's glyph's nodes can have negative co-ordinates, but the
// rasterizer clips anything left of x=0 or above y=0. xmin and ymin
// are the pixel offsets, based on the font's FUnit metrics, that let
// a negative co-ordinate in TrueType space be non-negative in
// rasterizer space. xmin and ymin are typically <= 0.
fx += raster.Fix32(-xmin << 8)
fy += raster.Fix32(-ymin << 8)
// Rasterize the glyph's vectors.
c.r.Clear()
e0 := 0
for _, e1 := range c.glyphBuf.End {
c.drawContour(c.glyphBuf.Point[e0:e1], fx, fy)
e0 = e1
}
a := image.NewAlpha(image.Rect(0, 0, xmax-xmin, ymax-ymin))
c.r.Rasterize(raster.NewAlphaSrcPainter(a))
return a, image.Point{xmin, ymin}, nil
}
func main() {
// Draw a rounded corner that is one pixel wide.
r := raster.NewRasterizer(50, 50)
r.Start(p(5, 5))
r.Add1(p(5, 25))
r.Add2(p(5, 45), p(25, 45))
r.Add1(p(45, 45))
r.Add1(p(45, 44))
r.Add1(p(26, 44))
r.Add2(p(6, 44), p(6, 24))
r.Add1(p(6, 5))
r.Add1(p(5, 5))
// Rasterize that curve multiple times at different gammas.
const (
w = 600
h = 200
)
rgba := image.NewRGBA(image.Rect(0, 0, w, h))
draw.Draw(rgba, image.Rect(0, 0, w, h/2), image.Black, image.ZP, draw.Src)
draw.Draw(rgba, image.Rect(0, h/2, w, h), image.White, image.ZP, draw.Src)
mask := image.NewAlpha(image.Rect(0, 0, 50, 50))
painter := raster.NewAlphaSrcPainter(mask)
gammas := []float64{1.0 / 10.0, 1.0 / 3.0, 1.0 / 2.0, 2.0 / 3.0, 4.0 / 5.0, 1.0, 5.0 / 4.0, 3.0 / 2.0, 2.0, 3.0, 10.0}
for i, g := range gammas {
draw.Draw(mask, mask.Bounds(), image.Transparent, image.ZP, draw.Src)
r.Rasterize(raster.NewGammaCorrectionPainter(painter, g))
x, y := 50*i+25, 25
draw.DrawMask(rgba, image.Rect(x, y, x+50, y+50), image.White, image.ZP, mask, image.ZP, draw.Over)
y += 100
draw.DrawMask(rgba, image.Rect(x, y, x+50, y+50), image.Black, image.ZP, mask, image.ZP, draw.Over)
}
// Save that RGBA image to disk.
f, err := os.Create("out.png")
if err != nil {
log.Println(err)
os.Exit(1)
}
defer f.Close()
b := bufio.NewWriter(f)
err = png.Encode(b, rgba)
if err != nil {
log.Println(err)
os.Exit(1)
}
err = b.Flush()
if err != nil {
log.Println(err)
os.Exit(1)
}
fmt.Println("Wrote out.png OK.")
}
func main() {
// Rasterize the contours to a mask image.
const (
w = 400
h = 400
)
r := raster.NewRasterizer(w, h)
contour(r, outside)
contour(r, inside)
mask := image.NewAlpha(image.Rect(0, 0, w, h))
p := raster.NewAlphaSrcPainter(mask)
r.Rasterize(p)
// Draw the mask image (in gray) onto an RGBA image.
rgba := image.NewRGBA(image.Rect(0, 0, w, h))
gray := image.NewUniform(color.Alpha{0x1f})
draw.Draw(rgba, rgba.Bounds(), image.Black, image.ZP, draw.Src)
draw.DrawMask(rgba, rgba.Bounds(), gray, image.ZP, mask, image.ZP, draw.Over)
showNodes(rgba, outside)
showNodes(rgba, inside)
// Save that RGBA image to disk.
f, err := os.Create("out.png")
if err != nil {
log.Println(err)
os.Exit(1)
}
defer f.Close()
b := bufio.NewWriter(f)
err = png.Encode(b, rgba)
if err != nil {
log.Println(err)
os.Exit(1)
}
err = b.Flush()
if err != nil {
log.Println(err)
os.Exit(1)
}
fmt.Println("Wrote out.png OK.")
}