39 lines
1.3 KiB
C
39 lines
1.3 KiB
C
/*
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* Copyright (c) 2014, 2015 Jonas 'Sortie' Termansen.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* pixel.c
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* Pixel utilities.
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*/
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#include <stdint.h>
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#include "pixel.h"
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uint32_t blend_pixel(uint32_t bg_value, uint32_t fg_value)
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{
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union color_rgba8 fg; fg.value = fg_value;
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union color_rgba8 bg; bg.value = bg_value;
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if ( fg.a == 255 )
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return fg.value;
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if ( fg.a == 0 )
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return bg.value;
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union color_rgba8 ret;
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ret.a = 255;
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ret.r = ((255-fg.a)*bg.r + fg.a*fg.r) / 256;
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ret.g = ((255-fg.a)*bg.g + fg.a*fg.g) / 256;
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ret.b = ((255-fg.a)*bg.b + fg.a*fg.b) / 256;
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return ret.value;
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}
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