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+// Copyright 2010 Google Inc. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the COPYING file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS. All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+// -----------------------------------------------------------------------------
+//
+// inline YUV<->RGB conversion function
+//
+// The exact naming is Y'CbCr, following the ITU-R BT.601 standard.
+// More information at: http://en.wikipedia.org/wiki/YCbCr
+// Y = 0.2569 * R + 0.5044 * G + 0.0979 * B + 16
+// U = -0.1483 * R - 0.2911 * G + 0.4394 * B + 128
+// V = 0.4394 * R - 0.3679 * G - 0.0715 * B + 128
+// We use 16bit fixed point operations for RGB->YUV conversion (YUV_FIX).
+//
+// For the Y'CbCr to RGB conversion, the BT.601 specification reads:
+// R = 1.164 * (Y-16) + 1.596 * (V-128)
+// G = 1.164 * (Y-16) - 0.813 * (V-128) - 0.391 * (U-128)
+// B = 1.164 * (Y-16) + 2.018 * (U-128)
+// where Y is in the [16,235] range, and U/V in the [16,240] range.
+//
+// The fixed-point implementation used here is:
+// R = (19077 . y + 26149 . v - 14234) >> 6
+// G = (19077 . y - 6419 . u - 13320 . v + 8708) >> 6
+// B = (19077 . y + 33050 . u - 17685) >> 6
+// where the '.' operator is the mulhi_epu16 variant:
+// a . b = ((a << 8) * b) >> 16
+// that preserves 8 bits of fractional precision before final descaling.
+
+// Author: Skal (pascal.massimino@gmail.com)
+
+#ifndef WEBP_DSP_YUV_H_
+#define WEBP_DSP_YUV_H_
+
+#include "./dsp.h"
+#include "../dec/vp8_dec.h"
+
+#if defined(WEBP_EXPERIMENTAL_FEATURES)
+// Do NOT activate this feature for real compression. This is only experimental!
+// This flag is for comparison purpose against JPEG's "YUVj" natural colorspace.
+// This colorspace is close to Rec.601's Y'CbCr model with the notable
+// difference of allowing larger range for luma/chroma.
+// See http://en.wikipedia.org/wiki/YCbCr#JPEG_conversion paragraph, and its
+// difference with http://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion
+// #define USE_YUVj
+#endif
+
+//------------------------------------------------------------------------------
+// YUV -> RGB conversion
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+enum {
+ YUV_FIX = 16, // fixed-point precision for RGB->YUV
+ YUV_HALF = 1 << (YUV_FIX - 1),
+ YUV_MASK = (256 << YUV_FIX) - 1,
+ YUV_RANGE_MIN = -227, // min value of r/g/b output
+ YUV_RANGE_MAX = 256 + 226, // max value of r/g/b output
+
+ YUV_FIX2 = 6, // fixed-point precision for YUV->RGB
+ YUV_HALF2 = 1 << YUV_FIX2 >> 1,
+ YUV_MASK2 = (256 << YUV_FIX2) - 1
+};
+
+//------------------------------------------------------------------------------
+// slower on x86 by ~7-8%, but bit-exact with the SSE2/NEON version
+
+static WEBP_INLINE int MultHi(int v, int coeff) { // _mm_mulhi_epu16 emulation
+ return (v * coeff) >> 8;
+}
+
+static WEBP_INLINE int VP8Clip8(int v) {
+ return ((v & ~YUV_MASK2) == 0) ? (v >> YUV_FIX2) : (v < 0) ? 0 : 255;
+}
+
+static WEBP_INLINE int VP8YUVToR(int y, int v) {
+ return VP8Clip8(MultHi(y, 19077) + MultHi(v, 26149) - 14234);
+}
+
+static WEBP_INLINE int VP8YUVToG(int y, int u, int v) {
+ return VP8Clip8(MultHi(y, 19077) - MultHi(u, 6419) - MultHi(v, 13320) + 8708);
+}
+
+static WEBP_INLINE int VP8YUVToB(int y, int u) {
+ return VP8Clip8(MultHi(y, 19077) + MultHi(u, 33050) - 17685);
+}
+
+static WEBP_INLINE void VP8YuvToRgb(int y, int u, int v,
+ uint8_t* const rgb) {
+ rgb[0] = VP8YUVToR(y, v);
+ rgb[1] = VP8YUVToG(y, u, v);
+ rgb[2] = VP8YUVToB(y, u);
+}
+
+static WEBP_INLINE void VP8YuvToBgr(int y, int u, int v,
+ uint8_t* const bgr) {
+ bgr[0] = VP8YUVToB(y, u);
+ bgr[1] = VP8YUVToG(y, u, v);
+ bgr[2] = VP8YUVToR(y, v);
+}
+
+static WEBP_INLINE void VP8YuvToRgb565(int y, int u, int v,
+ uint8_t* const rgb) {
+ const int r = VP8YUVToR(y, v); // 5 usable bits
+ const int g = VP8YUVToG(y, u, v); // 6 usable bits
+ const int b = VP8YUVToB(y, u); // 5 usable bits
+ const int rg = (r & 0xf8) | (g >> 5);
+ const int gb = ((g << 3) & 0xe0) | (b >> 3);
+#ifdef WEBP_SWAP_16BIT_CSP
+ rgb[0] = gb;
+ rgb[1] = rg;
+#else
+ rgb[0] = rg;
+ rgb[1] = gb;
+#endif
+}
+
+static WEBP_INLINE void VP8YuvToRgba4444(int y, int u, int v,
+ uint8_t* const argb) {
+ const int r = VP8YUVToR(y, v); // 4 usable bits
+ const int g = VP8YUVToG(y, u, v); // 4 usable bits
+ const int b = VP8YUVToB(y, u); // 4 usable bits
+ const int rg = (r & 0xf0) | (g >> 4);
+ const int ba = (b & 0xf0) | 0x0f; // overwrite the lower 4 bits
+#ifdef WEBP_SWAP_16BIT_CSP
+ argb[0] = ba;
+ argb[1] = rg;
+#else
+ argb[0] = rg;
+ argb[1] = ba;
+#endif
+}
+
+//-----------------------------------------------------------------------------
+// Alpha handling variants
+
+static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v,
+ uint8_t* const argb) {
+ argb[0] = 0xff;
+ VP8YuvToRgb(y, u, v, argb + 1);
+}
+
+static WEBP_INLINE void VP8YuvToBgra(uint8_t y, uint8_t u, uint8_t v,
+ uint8_t* const bgra) {
+ VP8YuvToBgr(y, u, v, bgra);
+ bgra[3] = 0xff;
+}
+
+static WEBP_INLINE void VP8YuvToRgba(uint8_t y, uint8_t u, uint8_t v,
+ uint8_t* const rgba) {
+ VP8YuvToRgb(y, u, v, rgba);
+ rgba[3] = 0xff;
+}
+
+// Must be called before everything, to initialize the tables.
+void VP8YUVInit(void);
+
+//-----------------------------------------------------------------------------
+// SSE2 extra functions (mostly for upsampling_sse2.c)
+
+#if defined(WEBP_USE_SSE2)
+
+// Process 32 pixels and store the result (16b, 24b or 32b per pixel) in *dst.
+void VP8YuvToRgba32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
+ uint8_t* dst);
+void VP8YuvToRgb32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
+ uint8_t* dst);
+void VP8YuvToBgra32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
+ uint8_t* dst);
+void VP8YuvToBgr32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
+ uint8_t* dst);
+void VP8YuvToArgb32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
+ uint8_t* dst);
+void VP8YuvToRgba444432(const uint8_t* y, const uint8_t* u, const uint8_t* v,
+ uint8_t* dst);
+void VP8YuvToRgb56532(const uint8_t* y, const uint8_t* u, const uint8_t* v,
+ uint8_t* dst);
+
+#endif // WEBP_USE_SSE2
+
+//------------------------------------------------------------------------------
+// RGB -> YUV conversion
+
+// Stub functions that can be called with various rounding values:
+static WEBP_INLINE int VP8ClipUV(int uv, int rounding) {
+ uv = (uv + rounding + (128 << (YUV_FIX + 2))) >> (YUV_FIX + 2);
+ return ((uv & ~0xff) == 0) ? uv : (uv < 0) ? 0 : 255;
+}
+
+#ifndef USE_YUVj
+
+static WEBP_INLINE int VP8RGBToY(int r, int g, int b, int rounding) {
+ const int luma = 16839 * r + 33059 * g + 6420 * b;
+ return (luma + rounding + (16 << YUV_FIX)) >> YUV_FIX; // no need to clip
+}
+
+static WEBP_INLINE int VP8RGBToU(int r, int g, int b, int rounding) {
+ const int u = -9719 * r - 19081 * g + 28800 * b;
+ return VP8ClipUV(u, rounding);
+}
+
+static WEBP_INLINE int VP8RGBToV(int r, int g, int b, int rounding) {
+ const int v = +28800 * r - 24116 * g - 4684 * b;
+ return VP8ClipUV(v, rounding);
+}
+
+#else
+
+// This JPEG-YUV colorspace, only for comparison!
+// These are also 16bit precision coefficients from Rec.601, but with full
+// [0..255] output range.
+static WEBP_INLINE int VP8RGBToY(int r, int g, int b, int rounding) {
+ const int luma = 19595 * r + 38470 * g + 7471 * b;
+ return (luma + rounding) >> YUV_FIX; // no need to clip
+}
+
+static WEBP_INLINE int VP8RGBToU(int r, int g, int b, int rounding) {
+ const int u = -11058 * r - 21710 * g + 32768 * b;
+ return VP8ClipUV(u, rounding);
+}
+
+static WEBP_INLINE int VP8RGBToV(int r, int g, int b, int rounding) {
+ const int v = 32768 * r - 27439 * g - 5329 * b;
+ return VP8ClipUV(v, rounding);
+}
+
+#endif // USE_YUVj
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif /* WEBP_DSP_YUV_H_ */
generated by cgit v1.2.3 (git 2.26.2) at 2024-11-15 14:40:17 +0000