| 42 | } |
| 43 | |
| 44 | func drawLines(im *image.RGBA, c Color, lines []Scanline) { |
| 45 | const m = 0xffff |
| 46 | sr, sg, sb, sa := c.NRGBA().RGBA() |
| 47 | for _, line := range lines { |
| 48 | ma := line.Alpha |
| 49 | a := (m - sa*ma/m) * 0x101 |
| 50 | i := im.PixOffset(line.X1, line.Y) |
| 51 | for x := line.X1; x <= line.X2; x++ { |
| 52 | dr := uint32(im.Pix[i+0]) |
| 53 | dg := uint32(im.Pix[i+1]) |
| 54 | db := uint32(im.Pix[i+2]) |
| 55 | da := uint32(im.Pix[i+3]) |
| 56 | im.Pix[i+0] = uint8((dr*a + sr*ma) / m >> 8) |
| 57 | im.Pix[i+1] = uint8((dg*a + sg*ma) / m >> 8) |
| 58 | im.Pix[i+2] = uint8((db*a + sb*ma) / m >> 8) |
| 59 | im.Pix[i+3] = uint8((da*a + sa*ma) / m >> 8) |
| 60 | i += 4 |
| 61 | } |
| 62 | } |
| 63 | } |
| 64 | |
| 65 | func differenceFull(a, b *image.RGBA) float64 { |
| 66 | size := a.Bounds().Size() |