mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2026-11-06 21:37:26 +00:00
Michael Niedermayer
0293b8a027
Blending took the colour's own alpha as the value written into the alpha plane, weighted by that same alpha once more, so a translucent colour left less alpha behind than it covered: half transparent red over a transparent canvas ended with alpha 64 instead of 128, and drawn over opaque content it even punched a hole into the alpha plane. The colour's transparency is already part of the coverage, so the alpha plane takes full coverage, which is source-over compositing. The drawutils test program checks this and runs under FATE. Assisted-by: Claude
70 lines
2.3 KiB
C
70 lines
2.3 KiB
C
/*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <stdio.h>
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#include "libavutil/pixdesc.h"
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#include "libavfilter/drawutils.h"
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int main(void)
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{
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enum AVPixelFormat f;
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const AVPixFmtDescriptor *desc;
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FFDrawContext draw;
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FFDrawColor color;
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int r, i;
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for (f = 0; av_pix_fmt_desc_get(f); f++) {
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desc = av_pix_fmt_desc_get(f);
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if (!desc->name)
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continue;
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printf("Testing %s...%*s", desc->name,
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(int)(16 - strlen(desc->name)), "");
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r = ff_draw_init(&draw, f, 0);
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if (r < 0) {
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printf("no: %s\n", av_err2str(r));
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continue;
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}
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ff_draw_color(&draw, &color, (uint8_t[]) { 1, 0, 0, 1 });
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for (i = 0; i < sizeof(color); i++)
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if (((uint8_t *)&color)[i] != 128)
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break;
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if (i == sizeof(color)) {
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printf("fallback color\n");
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continue;
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}
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printf("ok\n");
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}
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ff_draw_init(&draw, AV_PIX_FMT_RGBA, FF_DRAW_PROCESS_ALPHA);
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ff_draw_color(&draw, &color, (uint8_t[]) { 255, 0, 0, 128 });
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for (int pass = 0; pass < 2; pass++) {
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uint8_t pixel[4] = { 0 };
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uint8_t *dst[4] = { pixel }, mask = 0xFF;
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int linesize[4] = { 4 };
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if (pass)
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ff_blend_rectangle(&draw, &color, dst, linesize, 1, 1, 0, 0, 1, 1);
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else
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ff_blend_mask(&draw, &color, dst, linesize, 1, 1, &mask, 1, 1, 1, 3, 0, 0, 0);
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printf("half transparent red over transparent rgba by %s: %d %d %d %d\n",
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pass ? "rectangle" : "mask", pixel[0], pixel[1], pixel[2], pixel[3]);
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}
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return 0;
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}
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