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Optimise 'simple' frame mixing

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jdgleaver 2020-11-09 12:27:34 +00:00
parent fce2e5a6a9
commit ef82b5b2fb
1 changed files with 5 additions and 26 deletions
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31
libgambatte/libretro/libretro.cpp
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@ -128,34 +128,13 @@ static void blend_frames_mix(void)
/* Store colours for next frame */
*(prev + x) = rgb_curr;
/* Unpack colours */
/* Mix colours
* > "Mixing Packed RGB Pixels Efficiently"
* http://blargg.8bitalley.com/info/rgb_mixing.html */
#ifdef VIDEO_RGB565
gambatte::video_pixel_t r_curr = rgb_curr >> 11 & 0x1F;
gambatte::video_pixel_t g_curr = rgb_curr >> 6 & 0x1F;
gambatte::video_pixel_t b_curr = rgb_curr & 0x1F;
gambatte::video_pixel_t r_prev = rgb_prev >> 11 & 0x1F;
gambatte::video_pixel_t g_prev = rgb_prev >> 6 & 0x1F;
gambatte::video_pixel_t b_prev = rgb_prev & 0x1F;
*(curr + x) = (rgb_curr + rgb_prev + ((rgb_curr ^ rgb_prev) & 0x821)) >> 1;
#else
gambatte::video_pixel_t r_curr = rgb_curr >> 16 & 0x1F;
gambatte::video_pixel_t g_curr = rgb_curr >> 8 & 0x1F;
gambatte::video_pixel_t b_curr = rgb_curr & 0x1F;
gambatte::video_pixel_t r_prev = rgb_prev >> 16 & 0x1F;
gambatte::video_pixel_t g_prev = rgb_prev >> 8 & 0x1F;
gambatte::video_pixel_t b_prev = rgb_prev & 0x1F;
#endif
/* Mix colours */
gambatte::video_pixel_t r_mix = (r_curr >> 1) + (r_prev >> 1) + (((r_curr & 0x1) + (r_prev & 0x1)) >> 1);
gambatte::video_pixel_t g_mix = (g_curr >> 1) + (g_prev >> 1) + (((g_curr & 0x1) + (g_prev & 0x1)) >> 1);
gambatte::video_pixel_t b_mix = (b_curr >> 1) + (b_prev >> 1) + (((b_curr & 0x1) + (b_prev & 0x1)) >> 1);
/* Repack colours for current frame */
#ifdef VIDEO_RGB565
*(curr + x) = r_mix << 11 | g_mix << 6 | b_mix;
#else
*(curr + x) = r_mix << 16 | g_mix << 8 | b_mix;
*(curr + x) = (rgb_curr + rgb_prev + ((rgb_curr ^ rgb_prev) & 0x10101)) >> 1;
#endif
}