// Draw aligns r.Min in dst with pt in src and mask
// and then replaces the rectangle r in dst with the
// result of the Porter-Duff compositing operation
// ``(src in mask) over dst.'' If mask is nil, the operation
// simplifies to ``src over dst.''
// The implementation is simple and slow.
func Draw(dst Image, r Rectangle, src, mask image.Image, pt Point) {
// Plenty of room for optimizations here.
dx, dy := src.Width(), src.Height()
if mask != nil {
if dx > mask.Width() {
dx = mask.Width()
}
if dy > mask.Width() {
dy = mask.Width()
}
}
dx -= pt.X
dy -= pt.Y
if r.Dx() > dx {
r.Max.X = r.Min.X + dx
}
if r.Dy() > dy {
r.Max.Y = r.Min.Y + dy
}
x0, x1, dx := r.Min.X, r.Max.X, 1
y0, y1, dy := r.Min.Y, r.Max.Y, 1
if image.Image(dst) == src && r.Overlaps(r.Add(pt.Sub(r.Min))) {
// Rectangles overlap: process backward?
if pt.Y < r.Min.Y || pt.Y == r.Min.Y && pt.X < r.Min.X {
x0, x1, dx = x1-1, x0-1, -1
y0, y1, dy = y1-1, y0-1, -1
}
}
var out *image.RGBA64Color
for y := y0; y != y1; y += dy {
for x := x0; x != x1; x += dx {
sx := pt.X + x - r.Min.X
sy := pt.Y + y - r.Min.Y
if mask == nil {
dst.Set(x, y, src.At(sx, sy))
continue
}
_, _, _, ma := mask.At(sx, sy).RGBA()
switch ma {
case 0:
continue
case 0xFFFFFFFF:
dst.Set(x, y, src.At(sx, sy))
default:
dr, dg, db, da := dst.At(x, y).RGBA()
dr >>= 16
dg >>= 16
db >>= 16
da >>= 16
sr, sg, sb, sa := src.At(sx, sy).RGBA()
sr >>= 16
sg >>= 16
sb >>= 16
sa >>= 16
ma >>= 16
const M = 1<<16 - 1
a := sa * ma / M
dr = (dr*(M-a) + sr*ma) / M
dg = (dg*(M-a) + sg*ma) / M
db = (db*(M-a) + sb*ma) / M
da = (da*(M-a) + sa*ma) / M
if out == nil {
out = new(image.RGBA64Color)
}
out.R = uint16(dr)
out.G = uint16(dg)
out.B = uint16(db)
out.A = uint16(da)
dst.Set(x, y, out)
}
}
}
}
// DrawMask aligns r.Min in dst with sp in src and mp in mask and then replaces the rectangle r
// in dst with the result of a Porter-Duff composition. A nil mask is treated as opaque.
func DrawMask(dst Image, r image.Rectangle, src image.Image, sp image.Point, mask image.Image, mp image.Point, op Op) {
clip(dst, &r, src, &sp, mask, &mp)
if r.Empty() {
return
}
// Fast paths for special cases. If none of them apply, then we fall back to a general but slow implementation.
if dst0, ok := dst.(*image.RGBA); ok {
if op == Over {
if mask == nil {
switch src0 := src.(type) {
case *image.ColorImage:
drawFillOver(dst0, r, src0)
return
case *image.RGBA:
drawCopyOver(dst0, r, src0, sp)
return
case *image.NRGBA:
drawNRGBAOver(dst0, r, src0, sp)
return
case *ycbcr.YCbCr:
drawYCbCr(dst0, r, src0, sp)
return
}
} else if mask0, ok := mask.(*image.Alpha); ok {
switch src0 := src.(type) {
case *image.ColorImage:
drawGlyphOver(dst0, r, src0, mask0, mp)
return
}
}
} else {
if mask == nil {
switch src0 := src.(type) {
case *image.ColorImage:
drawFillSrc(dst0, r, src0)
return
case *image.RGBA:
drawCopySrc(dst0, r, src0, sp)
return
case *image.NRGBA:
drawNRGBASrc(dst0, r, src0, sp)
return
case *ycbcr.YCbCr:
drawYCbCr(dst0, r, src0, sp)
return
}
}
}
drawRGBA(dst0, r, src, sp, mask, mp, op)
return
}
x0, x1, dx := r.Min.X, r.Max.X, 1
y0, y1, dy := r.Min.Y, r.Max.Y, 1
if image.Image(dst) == src && r.Overlaps(r.Add(sp.Sub(r.Min))) {
// Rectangles overlap: process backward?
if sp.Y < r.Min.Y || sp.Y == r.Min.Y && sp.X < r.Min.X {
x0, x1, dx = x1-1, x0-1, -1
y0, y1, dy = y1-1, y0-1, -1
}
}
var out *image.RGBA64Color
sy := sp.Y + y0 - r.Min.Y
my := mp.Y + y0 - r.Min.Y
for y := y0; y != y1; y, sy, my = y+dy, sy+dy, my+dy {
sx := sp.X + x0 - r.Min.X
mx := mp.X + x0 - r.Min.X
for x := x0; x != x1; x, sx, mx = x+dx, sx+dx, mx+dx {
ma := uint32(m)
if mask != nil {
_, _, _, ma = mask.At(mx, my).RGBA()
}
switch {
case ma == 0:
if op == Over {
// No-op.
} else {
dst.Set(x, y, zeroColor)
}
case ma == m && op == Src:
dst.Set(x, y, src.At(sx, sy))
default:
sr, sg, sb, sa := src.At(sx, sy).RGBA()
if out == nil {
out = new(image.RGBA64Color)
}
if op == Over {
dr, dg, db, da := dst.At(x, y).RGBA()
a := m - (sa * ma / m)
out.R = uint16((dr*a + sr*ma) / m)
out.G = uint16((dg*a + sg*ma) / m)
out.B = uint16((db*a + sb*ma) / m)
out.A = uint16((da*a + sa*ma) / m)
} else {
out.R = uint16(sr * ma / m)
out.G = uint16(sg * ma / m)
out.B = uint16(sb * ma / m)
out.A = uint16(sa * ma / m)
}
dst.Set(x, y, out)
}
}
}
}
// DrawMask aligns r.Min in dst with sp in src and mp in mask and then replaces the rectangle r
// in dst with the result of a Porter-Duff composition. A nil mask is treated as opaque.
// The implementation is simple and slow.
// TODO(nigeltao): Optimize this.
func DrawMask(dst Image, r Rectangle, src image.Image, sp Point, mask image.Image, mp Point, op Op) {
dx, dy := src.Width()-sp.X, src.Height()-sp.Y
if mask != nil {
if dx > mask.Width()-mp.X {
dx = mask.Width() - mp.X
}
if dy > mask.Height()-mp.Y {
dy = mask.Height() - mp.Y
}
}
if r.Dx() > dx {
r.Max.X = r.Min.X + dx
}
if r.Dy() > dy {
r.Max.Y = r.Min.Y + dy
}
// TODO(nigeltao): Clip r to dst's bounding box, and handle the case when sp or mp has negative X or Y.
// TODO(nigeltao): Ensure that r is well formed, i.e. r.Max.X >= r.Min.X and likewise for Y.
// Fast paths for special cases. If none of them apply, then we fall back to a general but slow implementation.
if dst0, ok := dst.(*image.RGBA); ok {
if op == Over {
// TODO(nigeltao): Implement a fast path for font glyphs (i.e. when mask is an image.Alpha).
} else {
if mask == nil {
if src0, ok := src.(image.ColorImage); ok {
drawFill(dst0, r, src0)
return
}
if src0, ok := src.(*image.RGBA); ok {
if dst0 == src0 && r.Overlaps(r.Add(sp.Sub(r.Min))) {
// TODO(nigeltao): Implement a fast path for the overlapping case.
} else {
drawCopy(dst0, r, src0, sp)
return
}
}
}
}
}
x0, x1, dx := r.Min.X, r.Max.X, 1
y0, y1, dy := r.Min.Y, r.Max.Y, 1
if image.Image(dst) == src && r.Overlaps(r.Add(sp.Sub(r.Min))) {
// Rectangles overlap: process backward?
if sp.Y < r.Min.Y || sp.Y == r.Min.Y && sp.X < r.Min.X {
x0, x1, dx = x1-1, x0-1, -1
y0, y1, dy = y1-1, y0-1, -1
}
}
var out *image.RGBA64Color
sy := sp.Y + y0 - r.Min.Y
my := mp.Y + y0 - r.Min.Y
for y := y0; y != y1; y, sy, my = y+dy, sy+dy, my+dy {
sx := sp.X + x0 - r.Min.X
mx := mp.X + x0 - r.Min.X
for x := x0; x != x1; x, sx, mx = x+dx, sx+dx, mx+dx {
// A nil mask is equivalent to a fully opaque, infinitely large mask.
// We work in 16-bit color, so that multiplying two values does not overflow a uint32.
const M = 1<<16 - 1
ma := uint32(M)
if mask != nil {
_, _, _, ma = mask.At(mx, my).RGBA()
ma >>= 16
}
switch {
case ma == 0:
if op == Over {
// No-op.
} else {
dst.Set(x, y, zeroColor)
}
case ma == M && op == Src:
dst.Set(x, y, src.At(sx, sy))
default:
sr, sg, sb, sa := src.At(sx, sy).RGBA()
sr >>= 16
sg >>= 16
sb >>= 16
sa >>= 16
if out == nil {
out = new(image.RGBA64Color)
}
if op == Over {
dr, dg, db, da := dst.At(x, y).RGBA()
dr >>= 16
dg >>= 16
db >>= 16
da >>= 16
a := M - (sa * ma / M)
out.R = uint16((dr*a + sr*ma) / M)
out.G = uint16((dg*a + sg*ma) / M)
out.B = uint16((db*a + sb*ma) / M)
out.A = uint16((da*a + sa*ma) / M)
} else {
out.R = uint16(sr * ma / M)
out.G = uint16(sg * ma / M)
out.B = uint16(sb * ma / M)
out.A = uint16(sa * ma / M)
}
dst.Set(x, y, out)
}
}
}
}