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vf_alphaextract.c
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1 /*
2  * Copyright (c) 2012 Steven Robertson
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 /**
22  * @file
23  * simple channel-swapping filter to get at the alpha component
24  */
25 
26 #include <string.h>
27 
28 #include "libavutil/pixfmt.h"
29 #include "avfilter.h"
30 #include "drawutils.h"
31 #include "internal.h"
32 #include "formats.h"
33 #include "video.h"
34 
35 enum { Y, U, V, A };
36 
37 typedef struct {
39  uint8_t rgba_map[4];
41 
43 {
44  static const enum AVPixelFormat in_fmts[] = {
48  };
49  static const enum AVPixelFormat out_fmts[] = { AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };
52  return 0;
53 }
54 
55 static int config_input(AVFilterLink *inlink)
56 {
57  AlphaExtractContext *extract = inlink->dst->priv;
58  extract->is_packed_rgb =
59  ff_fill_rgba_map(extract->rgba_map, inlink->format) >= 0;
60  return 0;
61 }
62 
63 static int filter_frame(AVFilterLink *inlink, AVFilterBufferRef *cur_buf)
64 {
65  AlphaExtractContext *extract = inlink->dst->priv;
66  AVFilterLink *outlink = inlink->dst->outputs[0];
67  AVFilterBufferRef *out_buf =
68  ff_get_video_buffer(outlink, AV_PERM_WRITE, outlink->w, outlink->h);
69  int ret;
70 
71  if (!out_buf) {
72  ret = AVERROR(ENOMEM);
73  goto end;
74  }
75  avfilter_copy_buffer_ref_props(out_buf, cur_buf);
76 
77  if (extract->is_packed_rgb) {
78  int x, y;
79  uint8_t *pcur, *pout;
80  for (y = 0; y < outlink->h; y++) {
81  pcur = cur_buf->data[0] + y * cur_buf->linesize[0] + extract->rgba_map[A];
82  pout = out_buf->data[0] + y * out_buf->linesize[0];
83  for (x = 0; x < outlink->w; x++) {
84  *pout = *pcur;
85  pout += 1;
86  pcur += 4;
87  }
88  }
89  } else {
90  const int linesize = abs(FFMIN(out_buf->linesize[Y], cur_buf->linesize[A]));
91  int y;
92  for (y = 0; y < outlink->h; y++) {
93  memcpy(out_buf->data[Y] + y * out_buf->linesize[Y],
94  cur_buf->data[A] + y * cur_buf->linesize[A],
95  linesize);
96  }
97  }
98 
99  ret = ff_filter_frame(outlink, out_buf);
100 
101 end:
102  avfilter_unref_buffer(cur_buf);
103  return ret;
104 }
105 
107  {
108  .name = "default",
109  .type = AVMEDIA_TYPE_VIDEO,
110  .config_props = config_input,
111  .filter_frame = filter_frame,
112  .min_perms = AV_PERM_READ,
113  },
114  { NULL }
115 };
116 
118  {
119  .name = "default",
120  .type = AVMEDIA_TYPE_VIDEO,
121  },
122  { NULL }
123 };
124 
126  .name = "alphaextract",
127  .description = NULL_IF_CONFIG_SMALL("Extract an alpha channel as a "
128  "grayscale image component."),
129  .priv_size = sizeof(AlphaExtractContext),
131  .inputs = alphaextract_inputs,
132  .outputs = alphaextract_outputs,
133 };