Exemplo n.º 1
0
// DrawMask将dst上的r.Min,src上的sp,mask上的mp对齐,然后对dst上的r型矩阵区域执行Porter-Duff合并操作。
// mask设置为nil就代表完全不透明。
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.
	switch dst0 := dst.(type) {
	case *image.RGBA:
		if op == Over {
			if mask == nil {
				switch src0 := src.(type) {
				case *image.Uniform:
					drawFillOver(dst0, r, src0)
					return
				case *image.RGBA:
					drawCopyOver(dst0, r, src0, sp)
					return
				case *image.NRGBA:
					drawNRGBAOver(dst0, r, src0, sp)
					return
				case *image.YCbCr:
					// An image.YCbCr is always fully opaque, and so if the
					// mask is nil (i.e. fully opaque) then the op is
					// effectively always Src. Similarly for image.Gray and
					// image.CMYK.
					if imageutil.DrawYCbCr(dst0, r, src0, sp) {
						return
					}
				case *image.Gray:
					drawGray(dst0, r, src0, sp)
					return
				case *image.CMYK:
					drawCMYK(dst0, r, src0, sp)
					return
				}
			} else if mask0, ok := mask.(*image.Alpha); ok {
				switch src0 := src.(type) {
				case *image.Uniform:
					drawGlyphOver(dst0, r, src0, mask0, mp)
					return
				}
			}
		} else {
			if mask == nil {
				switch src0 := src.(type) {
				case *image.Uniform:
					drawFillSrc(dst0, r, src0)
					return
				case *image.RGBA:
					drawCopySrc(dst0, r, src0, sp)
					return
				case *image.NRGBA:
					drawNRGBASrc(dst0, r, src0, sp)
					return
				case *image.YCbCr:
					if imageutil.DrawYCbCr(dst0, r, src0, sp) {
						return
					}
				case *image.Gray:
					drawGray(dst0, r, src0, sp)
					return
				case *image.CMYK:
					drawCMYK(dst0, r, src0, sp)
					return
				}
			}
		}
		drawRGBA(dst0, r, src, sp, mask, mp, op)
		return
	case *image.Paletted:
		if op == Src && mask == nil && !processBackward(dst, r, src, sp) {
			drawPaletted(dst0, r, src, sp, false)
			return
		}
	}

	x0, x1, dx := r.Min.X, r.Max.X, 1
	y0, y1, dy := r.Min.Y, r.Max.Y, 1
	if processBackward(dst, r, src, sp) {
		x0, x1, dx = x1-1, x0-1, -1
		y0, y1, dy = y1-1, y0-1, -1
	}

	var out color.RGBA64
	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, color.Transparent)
				}
			case ma == m && op == Src:
				dst.Set(x, y, src.At(sx, sy))
			default:
				sr, sg, sb, sa := src.At(sx, sy).RGBA()
				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)
				}
				// The third argument is &out instead of out (and out is
				// declared outside of the inner loop) to avoid the implicit
				// conversion to color.Color here allocating memory in the
				// inner loop if sizeof(color.RGBA64) > sizeof(uintptr).
				dst.Set(x, y, &out)
			}
		}
	}
}
Exemplo n.º 2
0
// applyBlack combines d.img3 and d.blackPix into a CMYK image. The formula
// used depends on whether the JPEG image is stored as CMYK or YCbCrK,
// indicated by the APP14 (Adobe) metadata.
//
// Adobe CMYK JPEG images are inverted, where 255 means no ink instead of full
// ink, so we apply "v = 255 - v" at various points. Note that a double
// inversion is a no-op, so inversions might be implicit in the code below.
func (d *decoder) applyBlack() (image.Image, error) {
	if !d.adobeTransformValid {
		return nil, UnsupportedError("unknown color model: 4-component JPEG doesn't have Adobe APP14 metadata")
	}

	// If the 4-component JPEG image isn't explicitly marked as "Unknown (RGB
	// or CMYK)" as per
	// http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html#Adobe
	// we assume that it is YCbCrK. This matches libjpeg's jdapimin.c.
	if d.adobeTransform != adobeTransformUnknown {
		// Convert the YCbCr part of the YCbCrK to RGB, invert the RGB to get
		// CMY, and patch in the original K. The RGB to CMY inversion cancels
		// out the 'Adobe inversion' described in the applyBlack doc comment
		// above, so in practice, only the fourth channel (black) is inverted.
		bounds := d.img3.Bounds()
		img := image.NewRGBA(bounds)
		imageutil.DrawYCbCr(img, bounds, d.img3, bounds.Min)
		for iBase, y := 0, bounds.Min.Y; y < bounds.Max.Y; iBase, y = iBase+img.Stride, y+1 {
			for i, x := iBase+3, bounds.Min.X; x < bounds.Max.X; i, x = i+4, x+1 {
				img.Pix[i] = 255 - d.blackPix[(y-bounds.Min.Y)*d.blackStride+(x-bounds.Min.X)]
			}
		}
		return &image.CMYK{
			Pix:    img.Pix,
			Stride: img.Stride,
			Rect:   img.Rect,
		}, nil
	}

	// The first three channels (cyan, magenta, yellow) of the CMYK
	// were decoded into d.img3, but each channel was decoded into a separate
	// []byte slice, and some channels may be subsampled. We interleave the
	// separate channels into an image.CMYK's single []byte slice containing 4
	// contiguous bytes per pixel.
	bounds := d.img3.Bounds()
	img := image.NewCMYK(bounds)

	translations := [4]struct {
		src    []byte
		stride int
	}{
		{d.img3.Y, d.img3.YStride},
		{d.img3.Cb, d.img3.CStride},
		{d.img3.Cr, d.img3.CStride},
		{d.blackPix, d.blackStride},
	}
	for t, translation := range translations {
		subsample := d.comp[t].h != d.comp[0].h || d.comp[t].v != d.comp[0].v
		for iBase, y := 0, bounds.Min.Y; y < bounds.Max.Y; iBase, y = iBase+img.Stride, y+1 {
			sy := y - bounds.Min.Y
			if subsample {
				sy /= 2
			}
			for i, x := iBase+t, bounds.Min.X; x < bounds.Max.X; i, x = i+4, x+1 {
				sx := x - bounds.Min.X
				if subsample {
					sx /= 2
				}
				img.Pix[i] = 255 - translation.src[sy*translation.stride+sx]
			}
		}
	}
	return img, nil
}