diff options
Diffstat (limited to 'src/pkg/exp/draw/draw.go')
| -rw-r--r-- | src/pkg/exp/draw/draw.go | 70 |
1 files changed, 40 insertions, 30 deletions
diff --git a/src/pkg/exp/draw/draw.go b/src/pkg/exp/draw/draw.go index 3455eacb9..d7722acfc 100644 --- a/src/pkg/exp/draw/draw.go +++ b/src/pkg/exp/draw/draw.go @@ -12,32 +12,37 @@ package draw import "image" +// A Porter-Duff compositing operator. +type Op int + +const SoverD Op = 0 + // A draw.Image is an image.Image with a Set method to change a single pixel. type Image interface { image.Image Set(x, y int, c image.Color) } -// 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. +// Draw calls DrawMask with a nil mask and an SoverD op. +func Draw(dst Image, r Rectangle, src image.Image, sp Point) { + DrawMask(dst, r, src, sp, nil, ZP, SoverD) +} - dx, dy := src.Width(), src.Height() +// 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. For the SoverD operator, the result +// is ``(src in mask) over dst''. If mask is nil, this simplifies to ``src over dst''. +// 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() { - dx = mask.Width() + if dx > mask.Width()-mp.X { + dx = mask.Width() - mp.X } - if dy > mask.Height() { - dy = mask.Height() + if dy > mask.Height()-mp.Y { + dy = mask.Height() - mp.Y } } - dx -= pt.X - dy -= pt.Y if r.Dx() > dx { r.Max.X = r.Min.X + dx } @@ -45,26 +50,31 @@ func Draw(dst Image, r Rectangle, src, mask image.Image, pt Point) { 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. + 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))) { + if image.Image(dst) == src && r.Overlaps(r.Add(sp.Sub(r.Min))) { // Rectangles overlap: process backward? - if pt.Y < r.Min.Y || pt.Y == r.Min.Y && pt.X < r.Min.X { + 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 - 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 + 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 { + // TODO(nigeltao): Check that op == SoverD. if mask == nil { dst.Set(x, y, src.At(sx, sy)) continue } - _, _, _, ma := mask.At(sx, sy).RGBA() + _, _, _, ma := mask.At(mx, my).RGBA() switch ma { case 0: continue @@ -109,17 +119,17 @@ func Border(dst Image, r Rectangle, w int, src image.Image, sp Point) { i := w if i > 0 { // inside r - Draw(dst, Rect(r.Min.X, r.Min.Y, r.Max.X, r.Min.Y+i), src, nil, sp) // top - Draw(dst, Rect(r.Min.X, r.Min.Y+i, r.Min.X+i, r.Max.Y-i), src, nil, sp.Add(Pt(0, i))) // left - Draw(dst, Rect(r.Max.X-i, r.Min.Y+i, r.Max.X, r.Max.Y-i), src, nil, sp.Add(Pt(r.Dx()-i, i))) // right - Draw(dst, Rect(r.Min.X, r.Max.Y-i, r.Max.X, r.Max.Y), src, nil, sp.Add(Pt(0, r.Dy()-i))) // bottom + Draw(dst, Rect(r.Min.X, r.Min.Y, r.Max.X, r.Min.Y+i), src, sp) // top + Draw(dst, Rect(r.Min.X, r.Min.Y+i, r.Min.X+i, r.Max.Y-i), src, sp.Add(Pt(0, i))) // left + Draw(dst, Rect(r.Max.X-i, r.Min.Y+i, r.Max.X, r.Max.Y-i), src, sp.Add(Pt(r.Dx()-i, i))) // right + Draw(dst, Rect(r.Min.X, r.Max.Y-i, r.Max.X, r.Max.Y), src, sp.Add(Pt(0, r.Dy()-i))) // bottom return } // outside r; i = -i - Draw(dst, Rect(r.Min.X-i, r.Min.Y-i, r.Max.X+i, r.Min.Y), src, nil, sp.Add(Pt(-i, -i))) // top - Draw(dst, Rect(r.Min.X-i, r.Min.Y, r.Min.X, r.Max.Y), src, nil, sp.Add(Pt(-i, 0))) // left - Draw(dst, Rect(r.Max.X, r.Min.Y, r.Max.X+i, r.Max.Y), src, nil, sp.Add(Pt(r.Dx(), 0))) // right - Draw(dst, Rect(r.Min.X-i, r.Max.Y, r.Max.X+i, r.Max.Y+i), src, nil, sp.Add(Pt(-i, 0))) // bottom + Draw(dst, Rect(r.Min.X-i, r.Min.Y-i, r.Max.X+i, r.Min.Y), src, sp.Add(Pt(-i, -i))) // top + Draw(dst, Rect(r.Min.X-i, r.Min.Y, r.Min.X, r.Max.Y), src, sp.Add(Pt(-i, 0))) // left + Draw(dst, Rect(r.Max.X, r.Min.Y, r.Max.X+i, r.Max.Y), src, sp.Add(Pt(r.Dx(), 0))) // right + Draw(dst, Rect(r.Min.X-i, r.Max.Y, r.Max.X+i, r.Max.Y+i), src, sp.Add(Pt(-i, 0))) // bottom } |