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Diffstat (limited to 'libgo/go/image/ycbcr/ycbcr.go')
| -rw-r--r-- | libgo/go/image/ycbcr/ycbcr.go | 184 |
1 files changed, 0 insertions, 184 deletions
diff --git a/libgo/go/image/ycbcr/ycbcr.go b/libgo/go/image/ycbcr/ycbcr.go deleted file mode 100644 index 84a35a3fb5e..00000000000 --- a/libgo/go/image/ycbcr/ycbcr.go +++ /dev/null @@ -1,184 +0,0 @@ -// Copyright 2011 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. - -// Package ycbcr provides images from the Y'CbCr color model. -// -// JPEG, VP8, the MPEG family and other codecs use this color model. Such -// codecs often use the terms YUV and Y'CbCr interchangeably, but strictly -// speaking, the term YUV applies only to analog video signals. -// -// Conversion between RGB and Y'CbCr is lossy and there are multiple, slightly -// different formulae for converting between the two. This package follows -// the JFIF specification at http://www.w3.org/Graphics/JPEG/jfif3.pdf. -package ycbcr - -import ( - "image" - "image/color" -) - -// RGBToYCbCr converts an RGB triple to a YCbCr triple. All components lie -// within the range [0, 255]. -func RGBToYCbCr(r, g, b uint8) (uint8, uint8, uint8) { - // The JFIF specification says: - // Y' = 0.2990*R + 0.5870*G + 0.1140*B - // Cb = -0.1687*R - 0.3313*G + 0.5000*B + 128 - // Cr = 0.5000*R - 0.4187*G - 0.0813*B + 128 - // http://www.w3.org/Graphics/JPEG/jfif3.pdf says Y but means Y'. - r1 := int(r) - g1 := int(g) - b1 := int(b) - yy := (19595*r1 + 38470*g1 + 7471*b1 + 1<<15) >> 16 - cb := (-11056*r1 - 21712*g1 + 32768*b1 + 257<<15) >> 16 - cr := (32768*r1 - 27440*g1 - 5328*b1 + 257<<15) >> 16 - if yy < 0 { - yy = 0 - } else if yy > 255 { - yy = 255 - } - if cb < 0 { - cb = 0 - } else if cb > 255 { - cb = 255 - } - if cr < 0 { - cr = 0 - } else if cr > 255 { - cr = 255 - } - return uint8(yy), uint8(cb), uint8(cr) -} - -// YCbCrToRGB converts a YCbCr triple to an RGB triple. All components lie -// within the range [0, 255]. -func YCbCrToRGB(y, cb, cr uint8) (uint8, uint8, uint8) { - // The JFIF specification says: - // R = Y' + 1.40200*(Cr-128) - // G = Y' - 0.34414*(Cb-128) - 0.71414*(Cr-128) - // B = Y' + 1.77200*(Cb-128) - // http://www.w3.org/Graphics/JPEG/jfif3.pdf says Y but means Y'. - yy1 := int(y)<<16 + 1<<15 - cb1 := int(cb) - 128 - cr1 := int(cr) - 128 - r := (yy1 + 91881*cr1) >> 16 - g := (yy1 - 22554*cb1 - 46802*cr1) >> 16 - b := (yy1 + 116130*cb1) >> 16 - if r < 0 { - r = 0 - } else if r > 255 { - r = 255 - } - if g < 0 { - g = 0 - } else if g > 255 { - g = 255 - } - if b < 0 { - b = 0 - } else if b > 255 { - b = 255 - } - return uint8(r), uint8(g), uint8(b) -} - -// YCbCrColor represents a fully opaque 24-bit Y'CbCr color, having 8 bits for -// each of one luma and two chroma components. -type YCbCrColor struct { - Y, Cb, Cr uint8 -} - -func (c YCbCrColor) RGBA() (uint32, uint32, uint32, uint32) { - r, g, b := YCbCrToRGB(c.Y, c.Cb, c.Cr) - return uint32(r) * 0x101, uint32(g) * 0x101, uint32(b) * 0x101, 0xffff -} - -func toYCbCrColor(c color.Color) color.Color { - if _, ok := c.(YCbCrColor); ok { - return c - } - r, g, b, _ := c.RGBA() - y, u, v := RGBToYCbCr(uint8(r>>8), uint8(g>>8), uint8(b>>8)) - return YCbCrColor{y, u, v} -} - -// YCbCrColorModel is the color model for YCbCrColor. -var YCbCrColorModel color.Model = color.ModelFunc(toYCbCrColor) - -// SubsampleRatio is the chroma subsample ratio used in a YCbCr image. -type SubsampleRatio int - -const ( - SubsampleRatio444 SubsampleRatio = iota - SubsampleRatio422 - SubsampleRatio420 -) - -// YCbCr is an in-memory image of YCbCr colors. There is one Y sample per pixel, -// but each Cb and Cr sample can span one or more pixels. -// YStride is the Y slice index delta between vertically adjacent pixels. -// CStride is the Cb and Cr slice index delta between vertically adjacent pixels -// that map to separate chroma samples. -// It is not an absolute requirement, but YStride and len(Y) are typically -// multiples of 8, and: -// For 4:4:4, CStride == YStride/1 && len(Cb) == len(Cr) == len(Y)/1. -// For 4:2:2, CStride == YStride/2 && len(Cb) == len(Cr) == len(Y)/2. -// For 4:2:0, CStride == YStride/2 && len(Cb) == len(Cr) == len(Y)/4. -type YCbCr struct { - Y []uint8 - Cb []uint8 - Cr []uint8 - YStride int - CStride int - SubsampleRatio SubsampleRatio - Rect image.Rectangle -} - -func (p *YCbCr) ColorModel() color.Model { - return YCbCrColorModel -} - -func (p *YCbCr) Bounds() image.Rectangle { - return p.Rect -} - -func (p *YCbCr) At(x, y int) color.Color { - if !(image.Point{x, y}.In(p.Rect)) { - return YCbCrColor{} - } - switch p.SubsampleRatio { - case SubsampleRatio422: - i := x / 2 - return YCbCrColor{ - p.Y[y*p.YStride+x], - p.Cb[y*p.CStride+i], - p.Cr[y*p.CStride+i], - } - case SubsampleRatio420: - i, j := x/2, y/2 - return YCbCrColor{ - p.Y[y*p.YStride+x], - p.Cb[j*p.CStride+i], - p.Cr[j*p.CStride+i], - } - } - // Default to 4:4:4 subsampling. - return YCbCrColor{ - p.Y[y*p.YStride+x], - p.Cb[y*p.CStride+x], - p.Cr[y*p.CStride+x], - } -} - -// SubImage returns an image representing the portion of the image p visible -// through r. The returned value shares pixels with the original image. -func (p *YCbCr) SubImage(r image.Rectangle) image.Image { - q := new(YCbCr) - *q = *p - q.Rect = q.Rect.Intersect(r) - return q -} - -func (p *YCbCr) Opaque() bool { - return true -} |