Adding upstream version 1.18.10.upstream/1.18.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 172 insertions, 0 deletions

diff --git a/src/image/internal/imageutil/gen.go b/src/image/internal/imageutil/gen.go
new file mode 100644
index 0000000..65e1e30
--- /dev/null
+++ b/src/image/internal/imageutil/gen.go
@@ -0,0 +1,172 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build ignore
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/format"
+	"log"
+	"os"
+)
+
+var debug = flag.Bool("debug", false, "")
+
+func main() {
+	flag.Parse()
+
+	w := new(bytes.Buffer)
+	w.WriteString(pre)
+	for _, sratio := range subsampleRatios {
+		fmt.Fprintf(w, sratioCase, sratio, sratioLines[sratio])
+	}
+	w.WriteString(post)
+
+	if *debug {
+		os.Stdout.Write(w.Bytes())
+		return
+	}
+	out, err := format.Source(w.Bytes())
+	if err != nil {
+		log.Fatal(err)
+	}
+	if err := os.WriteFile("impl.go", out, 0660); err != nil {
+		log.Fatal(err)
+	}
+}
+
+const pre = `// Code generated by go run gen.go; DO NOT EDIT.
+
+package imageutil
+
+import (
+	"image"
+)
+
+// DrawYCbCr draws the YCbCr source image on the RGBA destination image with
+// r.Min in dst aligned with sp in src. It reports whether the draw was
+// successful. If it returns false, no dst pixels were changed.
+//
+// This function assumes that r is entirely within dst's bounds and the
+// translation of r from dst coordinate space to src coordinate space is
+// entirely within src's bounds.
+func DrawYCbCr(dst *image.RGBA, r image.Rectangle, src *image.YCbCr, sp image.Point) (ok bool) {
+	// This function exists in the image/internal/imageutil package because it
+	// is needed by both the image/draw and image/jpeg packages, but it doesn't
+	// seem right for one of those two to depend on the other.
+	//
+	// Another option is to have this code be exported in the image package,
+	// but we'd need to make sure we're totally happy with the API (for the
+	// rest of Go 1 compatibility), and decide if we want to have a more
+	// general purpose DrawToRGBA method for other image types. One possibility
+	// is:
+	//
+	// func (src *YCbCr) CopyToRGBA(dst *RGBA, dr, sr Rectangle) (effectiveDr, effectiveSr Rectangle)
+	//
+	// in the spirit of the built-in copy function for 1-dimensional slices,
+	// that also allowed a CopyFromRGBA method if needed.
+
+	x0 := (r.Min.X - dst.Rect.Min.X) * 4
+	x1 := (r.Max.X - dst.Rect.Min.X) * 4
+	y0 := r.Min.Y - dst.Rect.Min.Y
+	y1 := r.Max.Y - dst.Rect.Min.Y
+	switch src.SubsampleRatio {
+`
+
+const post = `
+	default:
+		return false
+	}
+	return true
+}
+`
+
+const sratioCase = `
+	case image.YCbCrSubsampleRatio%s:
+		for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
+			dpix := dst.Pix[y*dst.Stride:]
+			yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)
+			%s
+
+				// This is an inline version of image/color/ycbcr.go's func YCbCrToRGB.
+				yy1 := int32(src.Y[yi]) * 0x10101
+				cb1 := int32(src.Cb[ci]) - 128
+				cr1 := int32(src.Cr[ci]) - 128
+
+				// The bit twiddling below is equivalent to
+				//
+				// r := (yy1 + 91881*cr1) >> 16
+				// if r < 0 {
+				//     r = 0
+				// } else if r > 0xff {
+				//     r = ^int32(0)
+				// }
+				//
+				// but uses fewer branches and is faster.
+				// Note that the uint8 type conversion in the return
+				// statement will convert ^int32(0) to 0xff.
+				// The code below to compute g and b uses a similar pattern.
+				r := yy1 + 91881*cr1
+				if uint32(r)&0xff000000 == 0 {
+					r >>= 16
+				} else {
+					r = ^(r >> 31)
+				}
+
+				g := yy1 - 22554*cb1 - 46802*cr1
+				if uint32(g)&0xff000000 == 0 {
+					g >>= 16
+				} else {
+					g = ^(g >> 31)
+				}
+
+				b := yy1 + 116130*cb1
+				if uint32(b)&0xff000000 == 0 {
+					b >>= 16
+				} else {
+					b = ^(b >> 31)
+				}
+
+
+				// use a temp slice to hint to the compiler that a single bounds check suffices
+				rgba := dpix[x : x+4 : len(dpix)]
+				rgba[0] = uint8(r)
+				rgba[1] = uint8(g)
+				rgba[2] = uint8(b)
+				rgba[3] = 255
+			}
+		}
+`
+
+var subsampleRatios = []string{
+	"444",
+	"422",
+	"420",
+	"440",
+}
+
+var sratioLines = map[string]string{
+	"444": `
+		ci := (sy-src.Rect.Min.Y)*src.CStride + (sp.X - src.Rect.Min.X)
+		for x := x0; x != x1; x, yi, ci = x+4, yi+1, ci+1 {
+	`,
+	"422": `
+		ciBase := (sy-src.Rect.Min.Y)*src.CStride - src.Rect.Min.X/2
+		for x, sx := x0, sp.X; x != x1; x, sx, yi = x+4, sx+1, yi+1 {
+			ci := ciBase + sx/2
+	`,
+	"420": `
+		ciBase := (sy/2-src.Rect.Min.Y/2)*src.CStride - src.Rect.Min.X/2
+		for x, sx := x0, sp.X; x != x1; x, sx, yi = x+4, sx+1, yi+1 {
+			ci := ciBase + sx/2
+	`,
+	"440": `
+		ci := (sy/2-src.Rect.Min.Y/2)*src.CStride + (sp.X - src.Rect.Min.X)
+		for x := x0; x != x1; x, yi, ci = x+4, yi+1, ci+1 {
+	`,
+}