lossless.h revision 1e7bf8805bd030c19924a5306837ecd72c295751 
1// Copyright 2012 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// Image transforms and color space conversion methods for lossless decoder.
9//
10// Authors: Vikas Arora (vikaas.arora@gmail.com)
11//          Jyrki Alakuijala (jyrki@google.com)
12
13#ifndef WEBP_DSP_LOSSLESS_H_
14#define WEBP_DSP_LOSSLESS_H_
15
16#include "webp/types.h"
17#include "webp/decode.h"
18
19#if defined(__cplusplus) || defined(c_plusplus)
20extern "C" {
21#endif
22
23//------------------------------------------------------------------------------
24// Image transforms.
25
26struct VP8LTransform;  // Defined in dec/vp8li.h.
27
28// Performs inverse transform of data given transform information, start and end
29// rows. Transform will be applied to rows [row_start, row_end[.
30// The *in and *out pointers refer to source and destination data respectively
31// corresponding to the intermediate row (row_start).
32void VP8LInverseTransform(const struct VP8LTransform* const transform,
33                          int row_start, int row_end,
34                          const uint32_t* const in, uint32_t* const out);
35
36// Subtracts green from blue and red channels.
37void VP8LSubtractGreenFromBlueAndRed(uint32_t* argb_data, int num_pixs);
38
39void VP8LResidualImage(int width, int height, int bits,
40                       uint32_t* const argb, uint32_t* const argb_scratch,
41                       uint32_t* const image);
42
43void VP8LColorSpaceTransform(int width, int height, int bits, int step,
44                             uint32_t* const argb, uint32_t* image);
45
46//------------------------------------------------------------------------------
47// Color space conversion.
48
49// Converts from BGRA to other color spaces.
50void VP8LConvertFromBGRA(const uint32_t* const in_data, int num_pixels,
51                         WEBP_CSP_MODE out_colorspace, uint8_t* const rgba);
52
53//------------------------------------------------------------------------------
54// Misc methods.
55
56// Computes sampled size of 'size' when sampling using 'sampling bits'.
57static WEBP_INLINE uint32_t VP8LSubSampleSize(uint32_t size,
58                                              uint32_t sampling_bits) {
59  return (size + (1 << sampling_bits) - 1) >> sampling_bits;
60}
61
62// Faster logarithm for integers. Small values use a look-up table.
63#define LOG_LOOKUP_IDX_MAX 256
64extern const float kLog2Table[LOG_LOOKUP_IDX_MAX];
65extern const float kSLog2Table[LOG_LOOKUP_IDX_MAX];
66extern float VP8LFastLog2Slow(int v);
67extern float VP8LFastSLog2Slow(int v);
68static WEBP_INLINE float VP8LFastLog2(int v) {
69  return (v < LOG_LOOKUP_IDX_MAX) ? kLog2Table[v] : VP8LFastLog2Slow(v);
70}
71// Fast calculation of v * log2(v) for integer input.
72static WEBP_INLINE float VP8LFastSLog2(int v) {
73  return (v < LOG_LOOKUP_IDX_MAX) ? kSLog2Table[v] : VP8LFastSLog2Slow(v);
74}
75
76
77// In-place difference of each component with mod 256.
78static WEBP_INLINE uint32_t VP8LSubPixels(uint32_t a, uint32_t b) {
79  const uint32_t alpha_and_green =
80      0x00ff00ffu + (a & 0xff00ff00u) - (b & 0xff00ff00u);
81  const uint32_t red_and_blue =
82      0xff00ff00u + (a & 0x00ff00ffu) - (b & 0x00ff00ffu);
83  return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);
84}
85
86//------------------------------------------------------------------------------
87
88#if defined(__cplusplus) || defined(c_plusplus)
89}    // extern "C"
90#endif
91
92#endif  // WEBP_DSP_LOSSLESS_H_
93