285 lines
9.7 KiB
C
285 lines
9.7 KiB
C
// 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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