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284 lines
9.7 KiB
284 lines
9.7 KiB
// Copyright 2010 Google Inc. All Rights Reserved. |
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// |
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// Use of this source code is governed by a BSD-style license |
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// that can be found in the COPYING file in the root of the source |
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// tree. An additional intellectual property rights grant can be found |
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// in the file PATENTS. All contributing project authors may |
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// be found in the AUTHORS file in the root of the source tree. |
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// ----------------------------------------------------------------------------- |
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// |
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// inline YUV<->RGB conversion function |
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// |
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// The exact naming is Y'CbCr, following the ITU-R BT.601 standard. |
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// More information at: http://en.wikipedia.org/wiki/YCbCr |
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// Y = 0.2569 * R + 0.5044 * G + 0.0979 * B + 16 |
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// U = -0.1483 * R - 0.2911 * G + 0.4394 * B + 128 |
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// V = 0.4394 * R - 0.3679 * G - 0.0715 * B + 128 |
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// We use 16bit fixed point operations for RGB->YUV conversion. |
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// |
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// For the Y'CbCr to RGB conversion, the BT.601 specification reads: |
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// R = 1.164 * (Y-16) + 1.596 * (V-128) |
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// G = 1.164 * (Y-16) - 0.813 * (V-128) - 0.391 * (U-128) |
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// B = 1.164 * (Y-16) + 2.018 * (U-128) |
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// where Y is in the [16,235] range, and U/V in the [16,240] range. |
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// In the table-lookup version (WEBP_YUV_USE_TABLE), the common factor |
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// "1.164 * (Y-16)" can be handled as an offset in the VP8kClip[] table. |
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// So in this case the formulae should be read as: |
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// R = 1.164 * [Y + 1.371 * (V-128) ] - 18.624 |
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// G = 1.164 * [Y - 0.698 * (V-128) - 0.336 * (U-128)] - 18.624 |
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// B = 1.164 * [Y + 1.733 * (U-128)] - 18.624 |
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// once factorized. Here too, 16bit fixed precision is used. |
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// |
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// Author: Skal (pascal.massimino@gmail.com) |
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#ifndef WEBP_DSP_YUV_H_ |
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#define WEBP_DSP_YUV_H_ |
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#include "../dec/decode_vp8.h" |
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// Define the following to use the LUT-based code: |
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#define WEBP_YUV_USE_TABLE |
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#if defined(WEBP_EXPERIMENTAL_FEATURES) |
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// Do NOT activate this feature for real compression. This is only experimental! |
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// This flag is for comparison purpose against JPEG's "YUVj" natural colorspace. |
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// This colorspace is close to Rec.601's Y'CbCr model with the notable |
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// difference of allowing larger range for luma/chroma. |
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// See http://en.wikipedia.org/wiki/YCbCr#JPEG_conversion paragraph, and its |
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// difference with http://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion |
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// #define USE_YUVj |
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#endif |
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//------------------------------------------------------------------------------ |
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// YUV -> RGB conversion |
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#if defined(__cplusplus) || defined(c_plusplus) |
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extern "C" { |
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#endif |
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enum { YUV_FIX = 16, // fixed-point precision |
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YUV_HALF = 1 << (YUV_FIX - 1), |
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YUV_MASK = (256 << YUV_FIX) - 1, |
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YUV_RANGE_MIN = -227, // min value of r/g/b output |
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YUV_RANGE_MAX = 256 + 226 // max value of r/g/b output |
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}; |
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#ifdef WEBP_YUV_USE_TABLE |
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extern int16_t VP8kVToR[256], VP8kUToB[256]; |
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extern int32_t VP8kVToG[256], VP8kUToG[256]; |
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extern uint8_t VP8kClip[YUV_RANGE_MAX - YUV_RANGE_MIN]; |
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extern uint8_t VP8kClip4Bits[YUV_RANGE_MAX - YUV_RANGE_MIN]; |
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static WEBP_INLINE void VP8YuvToRgb(uint8_t y, uint8_t u, uint8_t v, |
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uint8_t* const rgb) { |
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const int r_off = VP8kVToR[v]; |
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const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX; |
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const int b_off = VP8kUToB[u]; |
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rgb[0] = VP8kClip[y + r_off - YUV_RANGE_MIN]; |
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rgb[1] = VP8kClip[y + g_off - YUV_RANGE_MIN]; |
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rgb[2] = VP8kClip[y + b_off - YUV_RANGE_MIN]; |
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} |
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static WEBP_INLINE void VP8YuvToBgr(uint8_t y, uint8_t u, uint8_t v, |
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uint8_t* const bgr) { |
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const int r_off = VP8kVToR[v]; |
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const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX; |
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const int b_off = VP8kUToB[u]; |
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bgr[0] = VP8kClip[y + b_off - YUV_RANGE_MIN]; |
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bgr[1] = VP8kClip[y + g_off - YUV_RANGE_MIN]; |
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bgr[2] = VP8kClip[y + r_off - YUV_RANGE_MIN]; |
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} |
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static WEBP_INLINE void VP8YuvToRgb565(uint8_t y, uint8_t u, uint8_t v, |
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uint8_t* const rgb) { |
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const int r_off = VP8kVToR[v]; |
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const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX; |
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const int b_off = VP8kUToB[u]; |
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const uint8_t rg = ((VP8kClip[y + r_off - YUV_RANGE_MIN] & 0xf8) | |
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(VP8kClip[y + g_off - YUV_RANGE_MIN] >> 5)); |
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const uint8_t gb = (((VP8kClip[y + g_off - YUV_RANGE_MIN] << 3) & 0xe0) | |
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(VP8kClip[y + b_off - YUV_RANGE_MIN] >> 3)); |
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#ifdef WEBP_SWAP_16BIT_CSP |
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rgb[0] = gb; |
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rgb[1] = rg; |
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#else |
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rgb[0] = rg; |
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rgb[1] = gb; |
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#endif |
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} |
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static WEBP_INLINE void VP8YuvToRgba4444(uint8_t y, uint8_t u, uint8_t v, |
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uint8_t* const argb) { |
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const int r_off = VP8kVToR[v]; |
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const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX; |
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const int b_off = VP8kUToB[u]; |
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const uint8_t rg = ((VP8kClip4Bits[y + r_off - YUV_RANGE_MIN] << 4) | |
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VP8kClip4Bits[y + g_off - YUV_RANGE_MIN]); |
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const uint8_t ba = (VP8kClip4Bits[y + b_off - YUV_RANGE_MIN] << 4) | 0x0f; |
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#ifdef WEBP_SWAP_16BIT_CSP |
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argb[0] = ba; |
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argb[1] = rg; |
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#else |
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argb[0] = rg; |
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argb[1] = ba; |
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#endif |
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} |
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#else // Table-free version (slower on x86) |
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// These constants are 16b fixed-point version of ITU-R BT.601 constants |
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#define kYScale 76309 // 1.164 = 255 / 219 |
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#define kVToR 104597 // 1.596 = 255 / 112 * 0.701 |
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#define kUToG 25674 // 0.391 = 255 / 112 * 0.886 * 0.114 / 0.587 |
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#define kVToG 53278 // 0.813 = 255 / 112 * 0.701 * 0.299 / 0.587 |
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#define kUToB 132201 // 2.018 = 255 / 112 * 0.886 |
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#define kRCst (-kYScale * 16 - kVToR * 128 + YUV_HALF) |
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#define kGCst (-kYScale * 16 + kUToG * 128 + kVToG * 128 + YUV_HALF) |
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#define kBCst (-kYScale * 16 - kUToB * 128 + YUV_HALF) |
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static WEBP_INLINE uint8_t VP8Clip8(int v) { |
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return ((v & ~YUV_MASK) == 0) ? (uint8_t)(v >> YUV_FIX) |
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: (v < 0) ? 0u : 255u; |
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} |
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static WEBP_INLINE uint8_t VP8ClipN(int v, int N) { // clip to N bits |
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return ((v & ~YUV_MASK) == 0) ? (uint8_t)(v >> (YUV_FIX + (8 - N))) |
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: (v < 0) ? 0u : (255u >> (8 - N)); |
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} |
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static WEBP_INLINE int VP8YUVToR(int y, int v) { |
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return kYScale * y + kVToR * v + kRCst; |
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} |
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static WEBP_INLINE int VP8YUVToG(int y, int u, int v) { |
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return kYScale * y - kUToG * u - kVToG * v + kGCst; |
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} |
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static WEBP_INLINE int VP8YUVToB(int y, int u) { |
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return kYScale * y + kUToB * u + kBCst; |
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} |
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static WEBP_INLINE void VP8YuvToRgb(uint8_t y, uint8_t u, uint8_t v, |
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uint8_t* const rgb) { |
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rgb[0] = VP8Clip8(VP8YUVToR(y, v)); |
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rgb[1] = VP8Clip8(VP8YUVToG(y, u, v)); |
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rgb[2] = VP8Clip8(VP8YUVToB(y, u)); |
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} |
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static WEBP_INLINE void VP8YuvToBgr(uint8_t y, uint8_t u, uint8_t v, |
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uint8_t* const bgr) { |
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bgr[0] = VP8Clip8(VP8YUVToB(y, u)); |
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bgr[1] = VP8Clip8(VP8YUVToG(y, u, v)); |
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bgr[2] = VP8Clip8(VP8YUVToR(y, v)); |
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} |
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static WEBP_INLINE void VP8YuvToRgb565(uint8_t y, uint8_t u, uint8_t v, |
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uint8_t* const rgb) { |
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const int r = VP8Clip8(VP8YUVToR(y, u)); |
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const int g = VP8ClipN(VP8YUVToG(y, u, v), 6); |
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const int b = VP8ClipN(VP8YUVToB(y, v), 5); |
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const uint8_t rg = (r & 0xf8) | (g >> 3); |
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const uint8_t gb = (g << 5) | b; |
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#ifdef WEBP_SWAP_16BIT_CSP |
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rgb[0] = gb; |
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rgb[1] = rg; |
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#else |
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rgb[0] = rg; |
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rgb[1] = gb; |
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#endif |
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} |
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static WEBP_INLINE void VP8YuvToRgba4444(uint8_t y, uint8_t u, uint8_t v, |
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uint8_t* const argb) { |
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const int r = VP8Clip8(VP8YUVToR(y, u)); |
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const int g = VP8ClipN(VP8YUVToG(y, u, v), 4); |
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const int b = VP8Clip8(VP8YUVToB(y, v)); |
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const uint8_t rg = (r & 0xf0) | g; |
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const uint8_t ba = b | 0x0f; // overwrite the lower 4 bits |
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#ifdef WEBP_SWAP_16BIT_CSP |
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argb[0] = ba; |
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argb[1] = rg; |
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#else |
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argb[0] = rg; |
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argb[1] = ba; |
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#endif |
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} |
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#endif // WEBP_YUV_USE_TABLE |
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static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v, |
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uint8_t* const argb) { |
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argb[0] = 0xff; |
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VP8YuvToRgb(y, u, v, argb + 1); |
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} |
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static WEBP_INLINE void VP8YuvToBgra(uint8_t y, uint8_t u, uint8_t v, |
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uint8_t* const bgra) { |
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VP8YuvToBgr(y, u, v, bgra); |
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bgra[3] = 0xff; |
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} |
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static WEBP_INLINE void VP8YuvToRgba(uint8_t y, uint8_t u, uint8_t v, |
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uint8_t* const rgba) { |
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VP8YuvToRgb(y, u, v, rgba); |
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rgba[3] = 0xff; |
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} |
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// Must be called before everything, to initialize the tables. |
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void VP8YUVInit(void); |
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//------------------------------------------------------------------------------ |
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// RGB -> YUV conversion |
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static WEBP_INLINE int VP8ClipUV(int v) { |
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v = (v + (257 << (YUV_FIX + 2 - 1))) >> (YUV_FIX + 2); |
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return ((v & ~0xff) == 0) ? v : (v < 0) ? 0 : 255; |
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} |
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#ifndef USE_YUVj |
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static WEBP_INLINE int VP8RGBToY(int r, int g, int b) { |
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const int kRound = (1 << (YUV_FIX - 1)) + (16 << YUV_FIX); |
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const int luma = 16839 * r + 33059 * g + 6420 * b; |
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return (luma + kRound) >> YUV_FIX; // no need to clip |
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} |
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static WEBP_INLINE int VP8RGBToU(int r, int g, int b) { |
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const int u = -9719 * r - 19081 * g + 28800 * b; |
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return VP8ClipUV(u); |
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} |
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static WEBP_INLINE int VP8RGBToV(int r, int g, int b) { |
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const int v = +28800 * r - 24116 * g - 4684 * b; |
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return VP8ClipUV(v); |
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} |
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#else |
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// This JPEG-YUV colorspace, only for comparison! |
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// These are also 16-bit precision coefficients from Rec.601, but with full |
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// [0..255] output range. |
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static WEBP_INLINE int VP8RGBToY(int r, int g, int b) { |
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const int kRound = (1 << (YUV_FIX - 1)); |
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const int luma = 19595 * r + 38470 * g + 7471 * b; |
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return (luma + kRound) >> YUV_FIX; // no need to clip |
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} |
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static WEBP_INLINE int VP8RGBToU(int r, int g, int b) { |
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const int u = -11058 * r - 21710 * g + 32768 * b; |
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return VP8ClipUV(u); |
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} |
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static WEBP_INLINE int VP8RGBToV(int r, int g, int b) { |
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const int v = 32768 * r - 27439 * g - 5329 * b; |
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return VP8ClipUV(v); |
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} |
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#endif // USE_YUVj |
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#if defined(__cplusplus) || defined(c_plusplus) |
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} // extern "C" |
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#endif |
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#endif /* WEBP_DSP_YUV_H_ */
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