FFmpeg
alphablend.c
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1 /*
2  * Copyright (C) 2015 Michael Niedermayer <michaelni@gmx.at>
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #include "swscale_internal.h"
22 
24  int srcStride[], int srcSliceY, int srcSliceH,
25  uint8_t *dst[], int dstStride[])
26 {
28  int nb_components = desc->nb_components;
29  int plane, x, y;
30  int plane_count = isGray(c->srcFormat) ? 1 : 3;
31  int sixteen_bits = desc->comp[0].depth >= 9;
32  unsigned off = 1<<(desc->comp[0].depth - 1);
33  unsigned shift = desc->comp[0].depth;
34  unsigned max = (1<<shift) - 1;
35  int target_table[2][3];
36 
37  for (plane = 0; plane < plane_count; plane++) {
38  int a = 0, b = 0;
40  a = (1<<(desc->comp[0].depth - 1))/2;
41  b = 3*(1<<(desc->comp[0].depth-1))/2;
42  }
43  target_table[0][plane] = plane && !(desc->flags & AV_PIX_FMT_FLAG_RGB) ? 1<<(desc->comp[0].depth - 1) : a;
44  target_table[1][plane] = plane && !(desc->flags & AV_PIX_FMT_FLAG_RGB) ? 1<<(desc->comp[0].depth - 1) : b;
45  }
46 
47  av_assert0(plane_count == nb_components - 1);
48  if (desc->flags & AV_PIX_FMT_FLAG_PLANAR) {
49  for (plane = 0; plane < plane_count; plane++) {
50  int w = plane ? c->chrSrcW : c->srcW;
51  int x_subsample = plane ? desc->log2_chroma_w: 0;
52  int y_subsample = plane ? desc->log2_chroma_h: 0;
53  for (y = srcSliceY >> y_subsample; y < AV_CEIL_RSHIFT(srcSliceH, y_subsample); y++) {
54  if (x_subsample || y_subsample) {
55  int alpha;
56  unsigned u;
57  if (sixteen_bits) {
58  ptrdiff_t alpha_step = srcStride[plane_count] >> 1;
59  const uint16_t *s = (const uint16_t *)(src[plane ] + srcStride[plane ] * y);
60  const uint16_t *a = (const uint16_t *)(src[plane_count] + (srcStride[plane_count] * y << y_subsample));
61  uint16_t *d = ( uint16_t *)(dst[plane ] + dstStride[plane ] * y);
62  if ((!isBE(c->srcFormat)) == !HAVE_BIGENDIAN) {
63  for (x = 0; x < w; x++) {
64  if (y_subsample) {
65  alpha = (a[2*x] + a[2*x + 1] + 2 +
66  a[2*x + alpha_step] + a[2*x + alpha_step + 1]) >> 2;
67  } else
68  alpha = (a[2*x] + a[2*x + 1]) >> 1;
69  u = s[x]*alpha + target_table[((x^y)>>5)&1][plane]*(max-alpha) + off;
70  d[x] = av_clip((u + (u >> shift)) >> shift, 0, max);
71  }
72  } else {
73  for (x = 0; x < w; x++) {
74  if (y_subsample) {
75  alpha = (av_bswap16(a[2*x]) + av_bswap16(a[2*x + 1]) + 2 +
76  av_bswap16(a[2*x + alpha_step]) + av_bswap16(a[2*x + alpha_step + 1])) >> 2;
77  } else
78  alpha = (av_bswap16(a[2*x]) + av_bswap16(a[2*x + 1])) >> 1;
79  u = av_bswap16(s[x])*alpha + target_table[((x^y)>>5)&1][plane]*(max-alpha) + off;
80  d[x] = av_clip((u + (u >> shift)) >> shift, 0, max);
81  }
82  }
83  } else {
84  ptrdiff_t alpha_step = srcStride[plane_count];
85  const uint8_t *s = src[plane ] + srcStride[plane] * y;
86  const uint8_t *a = src[plane_count] + (srcStride[plane_count] * y << y_subsample);
87  uint8_t *d = dst[plane ] + dstStride[plane] * y;
88  for (x = 0; x < w; x++) {
89  if (y_subsample) {
90  alpha = (a[2*x] + a[2*x + 1] + 2 +
91  a[2*x + alpha_step] + a[2*x + alpha_step + 1]) >> 2;
92  } else
93  alpha = (a[2*x] + a[2*x + 1]) >> 1;
94  u = s[x]*alpha + target_table[((x^y)>>5)&1][plane]*(255-alpha) + 128;
95  d[x] = (257*u) >> 16;
96  }
97  }
98  } else {
99  if (sixteen_bits) {
100  const uint16_t *s = (const uint16_t *)(src[plane ] + srcStride[plane ] * y);
101  const uint16_t *a = (const uint16_t *)(src[plane_count] + srcStride[plane_count] * y);
102  uint16_t *d = ( uint16_t *)(dst[plane ] + dstStride[plane ] * y);
103  if ((!isBE(c->srcFormat)) == !HAVE_BIGENDIAN) {
104  for (x = 0; x < w; x++) {
105  unsigned u = s[x]*a[x] + target_table[((x^y)>>5)&1][plane]*(max-a[x]) + off;
106  d[x] = av_clip((u + (u >> shift)) >> shift, 0, max);
107  }
108  } else {
109  for (x = 0; x < w; x++) {
110  unsigned aswap =av_bswap16(a[x]);
111  unsigned u = av_bswap16(s[x])*aswap + target_table[((x^y)>>5)&1][plane]*(max-aswap) + off;
112  d[x] = av_clip((u + (u >> shift)) >> shift, 0, max);
113  }
114  }
115  } else {
116  const uint8_t *s = src[plane ] + srcStride[plane] * y;
117  const uint8_t *a = src[plane_count] + srcStride[plane_count] * y;
118  uint8_t *d = dst[plane ] + dstStride[plane] * y;
119  for (x = 0; x < w; x++) {
120  unsigned u = s[x]*a[x] + target_table[((x^y)>>5)&1][plane]*(255-a[x]) + 128;
121  d[x] = (257*u) >> 16;
122  }
123  }
124  }
125  }
126  }
127  } else {
128  int alpha_pos = desc->comp[plane_count].offset;
129  int w = c->srcW;
130  for (y = srcSliceY; y < srcSliceH; y++) {
131  if (sixteen_bits) {
132  const uint16_t *s = (const uint16_t *)(src[0] + srcStride[0] * y + 2*!alpha_pos);
133  const uint16_t *a = (const uint16_t *)(src[0] + srcStride[0] * y + alpha_pos);
134  uint16_t *d = ( uint16_t *)(dst[0] + dstStride[0] * y);
135  if ((!isBE(c->srcFormat)) == !HAVE_BIGENDIAN) {
136  for (x = 0; x < w; x++) {
137  for (plane = 0; plane < plane_count; plane++) {
138  int x_index = (plane_count + 1) * x;
139  unsigned u = s[x_index + plane]*a[x_index] + target_table[((x^y)>>5)&1][plane]*(max-a[x_index]) + off;
140  d[plane_count*x + plane] = av_clip((u + (u >> shift)) >> shift, 0, max);
141  }
142  }
143  } else {
144  for (x = 0; x < w; x++) {
145  for (plane = 0; plane < plane_count; plane++) {
146  int x_index = (plane_count + 1) * x;
147  unsigned aswap =av_bswap16(a[x_index]);
148  unsigned u = av_bswap16(s[x_index + plane])*aswap + target_table[((x^y)>>5)&1][plane]*(max-aswap) + off;
149  d[plane_count*x + plane] = av_clip((u + (u >> shift)) >> shift, 0, max);
150  }
151  }
152  }
153  } else {
154  const uint8_t *s = src[0] + srcStride[0] * y + !alpha_pos;
155  const uint8_t *a = src[0] + srcStride[0] * y + alpha_pos;
156  uint8_t *d = dst[0] + dstStride[0] * y;
157  for (x = 0; x < w; x++) {
158  for (plane = 0; plane < plane_count; plane++) {
159  int x_index = (plane_count + 1) * x;
160  unsigned u = s[x_index + plane]*a[x_index] + target_table[((x^y)>>5)&1][plane]*(255-a[x_index]) + 128;
161  d[plane_count*x + plane] = (257*u) >> 16;
162  }
163  }
164  }
165  }
166  }
167 
168  return 0;
169 }
int plane
Definition: avisynth_c.h:384
static int shift(int a, int b)
Definition: sonic.c:82
const AVPixFmtDescriptor * av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
Definition: pixdesc.c:2522
const char * desc
Definition: nvenc.c:68
SwsAlphaBlend alphablend
#define av_bswap16
Definition: bswap.h:31
The reader does not expect b to be semantically here and if the code is changed by maybe adding a a division or other the signedness will almost certainly be mistaken To avoid this confusion a new type was SUINT is the C unsigned type but it holds a signed int to use the same example SUINT a
Definition: undefined.txt:36
#define src
Definition: vp8dsp.c:254
uint8_t log2_chroma_w
Amount to shift the luma width right to find the chroma width.
Definition: pixdesc.h:92
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
AVComponentDescriptor comp[4]
Parameters that describe how pixels are packed.
Definition: pixdesc.h:117
uint8_t
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
#define u(width, name, range_min, range_max)
Definition: cbs_h2645.c:252
#define max(a, b)
Definition: cuda_runtime.h:33
int ff_sws_alphablendaway(SwsContext *c, const uint8_t *src[], int srcStride[], int srcSliceY, int srcSliceH, uint8_t *dst[], int dstStride[])
Definition: alphablend.c:23
uint8_t log2_chroma_h
Amount to shift the luma height right to find the chroma height.
Definition: pixdesc.h:101
#define AV_PIX_FMT_FLAG_RGB
The pixel format contains RGB-like data (as opposed to YUV/grayscale).
Definition: pixdesc.h:148
uint64_t flags
Combination of AV_PIX_FMT_FLAG_...
Definition: pixdesc.h:106
uint8_t nb_components
The number of components each pixel has, (1-4)
Definition: pixdesc.h:83
#define b
Definition: input.c:41
uint8_t w
Definition: llviddspenc.c:38
#define s(width, name)
Definition: cbs_vp9.c:257
#define isGray(x)
Definition: swscale.c:40
static av_always_inline int isBE(enum AVPixelFormat pix_fmt)
Descriptor that unambiguously describes how the bits of a pixel are stored in the up to 4 data planes...
Definition: pixdesc.h:81
static const int16_t alpha[]
Definition: ilbcdata.h:55
int offset
Number of elements before the component of the first pixel.
Definition: pixdesc.h:47
enum AVPixelFormat srcFormat
Source pixel format.
int chrSrcW
Width of source chroma planes.
int depth
Number of bits in the component.
Definition: pixdesc.h:58
int srcW
Width of source luma/alpha planes.
#define AV_PIX_FMT_FLAG_PLANAR
At least one pixel component is not in the first data plane.
Definition: pixdesc.h:144
#define AV_CEIL_RSHIFT(a, b)
Definition: common.h:58