yMax := r.Max.Y - dst.Rect.Min.Y

	y := r.Min.Y - dst.Rect.Min.Y
	sy := sp.Y - src.Rect.Min.Y
	for ; y != yMax; y, sy = y+1, sy+1 {
		dpix := dst.Pix[y*dst.Stride:]
		spix := src.Pix[sy*src.Stride:]

		for i, si := i0, si0; i < i1; i, si = i+4, si+1 {
			p := spix[si]
			d := dpix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
			d[0] = p
			d[1] = p
			d[2] = p
			d[3] = 255

		b.WriteString(paletteStr)
		// Write an image with bounds 2x1 but tc.nPix pixels. If tc.nPix != 2
		// then this should result in an invalid GIF image. First, write a
		// magic 0x2c (image descriptor) byte, bounds=(0,0)-(2,1), a flags
		// byte, and 2-bit LZW literals.
		b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")
		if tc.nPix > 0 {
			enc := lzwEncode(make([]byte, tc.nPix))
			if len(enc)+tc.extraExisting > 0xff {

func uninterlace(m *image.Paletted) {
	var nPix []uint8
	dx := m.Bounds().Dx()
	dy := m.Bounds().Dy()
	nPix = make([]uint8, dx*dy)
	offset := 0 // steps through the input by sequential scan lines.
	for _, pass := range interlacing {
		nOffset := pass.start * dx // steps through the output as defined by pass.
		for y := pass.start; y < dy; y += pass.skip {
			copy(nPix[nOffset:nOffset+dx], m.Pix[offset:offset+dx])
			offset += dx

	}
	return totalLength
}

// RGBA is an in-memory image whose At method returns [color.RGBA] values.
type RGBA struct {
	// Pix holds the image's pixels, in R, G, B, A order. The pixel at
	// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*4].
	Pix []uint8
	// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
	Stride int
	// Rect is the image's bounds.
	Rect Rectangle
}

						a = 0x00
					}
					pix[i+0] = r
					pix[i+1] = g
					pix[i+2] = b
					pix[i+3] = a
					i += 4
					j += 3
				}
				pixOffset += nrgba.Stride
			} else {
				pix, i, j := rgba.Pix, pixOffset, 0
				for x := 0; x < width; x++ {
					pix[i+0] = cdat[j+0]
					pix[i+1] = cdat[j+1]
					pix[i+2] = cdat[j+2]
					pix[i+3] = 0xff
					i += 4
					j += 3
				}

			} else if nrgba != nil {
				stride, pix = nrgba.Stride, nrgba.Pix
			}
			if stride != 0 {
				j0 := (y - b.Min.Y) * stride
				j1 := j0 + b.Dx()*4
				for j := j0; j < j1; j += 4 {
					cr0[i+0] = pix[j+0]
					cr0[i+1] = pix[j+1]
					cr0[i+2] = pix[j+2]
					i += 3
				}
			} else {
				for x := b.Min.X; x < b.Max.X; x++ {
					r, g, b, _ := m.At(x, y).RGBA()
					cr0[i+0] = uint8(r >> 8)

			sj = ymax
		}
		offset := (sj-b.Min.Y)*m.Stride - b.Min.X*4
		for i := 0; i < 8; i++ {
			sx := p.X + i
			if sx > xmax {
				sx = xmax
			}
			pix := m.Pix[offset+sx*4:]
			yy, cb, cr := color.RGBToYCbCr(pix[0], pix[1], pix[2])
			yBlock[8*j+i] = int32(yy)
			cbBlock[8*j+i] = int32(cb)
			crBlock[8*j+i] = int32(cr)
		}
	}
}

	if rgba, ok := m.(*image.RGBA); ok {
		return &slowestRGBA{
			Pix:    append([]byte(nil), rgba.Pix...),
			Stride: rgba.Stride,
			Rect:   rgba.Rect,
		}
	}
	rgba := image.NewRGBA(m.Bounds())
	Draw(rgba, rgba.Bounds(), m, m.Bounds().Min, Src)
	return &slowestRGBA{
		Pix:    rgba.Pix,
		Stride: rgba.Stride,
		Rect:   rgba.Rect,
	}
}

func init() {

			if err := check(m0.Bounds(), m0.Cr, m1.Cr, m0.CStride, m1.CStride); err != nil {
				t.Errorf("%s (Cr): %v", tc, err)
				continue
			}
		case *image.Gray:
			m1 := m1.(*image.Gray)
			if err := check(m0.Bounds(), m0.Pix, m1.Pix, m0.Stride, m1.Stride); err != nil {
				t.Errorf("%s: %v", tc, err)
				continue
			}
		default:
			t.Errorf("%s: unexpected image type %T", tc, m0)
			continue
		}
	}
}

		yo := d.img3.YOffset(bounds.Min.X, y)
		co := d.img3.COffset(bounds.Min.X, y)
		for i, iMax := 0, bounds.Max.X-bounds.Min.X; i < iMax; i++ {
			img.Pix[po+4*i+0] = d.img3.Y[yo+i]
			img.Pix[po+4*i+1] = d.img3.Cb[co+i/cScale]
			img.Pix[po+4*i+2] = d.img3.Cr[co+i/cScale]
			img.Pix[po+4*i+3] = 255
		}
	}
	return img, nil
}

// Decode reads a JPEG image from r and returns it as an [image.Image].