yuv.c revision b6dbce6bfeaabde2a7b581c4c6888d532d32f3ac 
1// Copyright 2010 Google Inc. All Rights Reserved.
2//
3// This code is licensed under the same terms as WebM:
4//  Software License Agreement:  http://www.webmproject.org/license/software/
5//  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
6// -----------------------------------------------------------------------------
7//
8// YUV->RGB conversion function
9//
10// Author: Skal (pascal.massimino@gmail.com)
11
12#include "./yuv.h"
13
14#if defined(__cplusplus) || defined(c_plusplus)
15extern "C" {
16#endif
17
18enum { YUV_HALF = 1 << (YUV_FIX - 1) };
19
20int16_t VP8kVToR[256], VP8kUToB[256];
21int32_t VP8kVToG[256], VP8kUToG[256];
22uint8_t VP8kClip[YUV_RANGE_MAX - YUV_RANGE_MIN];
23uint8_t VP8kClip4Bits[YUV_RANGE_MAX - YUV_RANGE_MIN];
24
25static int done = 0;
26
27static WEBP_INLINE uint8_t clip(int v, int max_value) {
28  return v < 0 ? 0 : v > max_value ? max_value : v;
29}
30
31void VP8YUVInit(void) {
32  int i;
33  if (done) {
34    return;
35  }
36  for (i = 0; i < 256; ++i) {
37    VP8kVToR[i] = (89858 * (i - 128) + YUV_HALF) >> YUV_FIX;
38    VP8kUToG[i] = -22014 * (i - 128) + YUV_HALF;
39    VP8kVToG[i] = -45773 * (i - 128);
40    VP8kUToB[i] = (113618 * (i - 128) + YUV_HALF) >> YUV_FIX;
41  }
42  for (i = YUV_RANGE_MIN; i < YUV_RANGE_MAX; ++i) {
43    const int k = ((i - 16) * 76283 + YUV_HALF) >> YUV_FIX;
44    VP8kClip[i - YUV_RANGE_MIN] = clip(k, 255);
45    VP8kClip4Bits[i - YUV_RANGE_MIN] = clip((k + 8) >> 4, 15);
46  }
47  done = 1;
48}
49
50#if defined(__cplusplus) || defined(c_plusplus)
51}    // extern "C"
52#endif
53