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Experimented and found "smaller" math

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This commit is contained in:
Paul Peavyhouse 2019-10-19 04:04:07 -07:00
parent 04158b39cd
commit 649e438f0d
1 changed files with 7 additions and 14 deletions
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21
src/lv_misc/lv_color.h
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@ -303,26 +303,19 @@ static inline uint32_t lv_color_to32(lv_color_t color)
ret.ch.alpha = 0xFF;
return ret.full;
#elif LV_COLOR_DEPTH == 16
#if LV_COLOR_16_SWAP == 0
lv_color32_t ret;
/**
* Per https://docs.google.com/spreadsheets/d/1PppX8FJpddauAPasHwlNgIPGIuPGPNvRbhilIQ8w-7g/edit#gid=0
* Truly any of the listed multipliers and adders would work.
* The below numbers seem the most precise.
*/
ret.ch.red = ( color.ch.red * 8423 + 7 ) >> 10;
ret.ch.green = ( color.ch.green * 259 + 3 ) >> 6;
ret.ch.blue = ( color.ch.blue * 8423 + 7 ) >> 10;
ret.ch.alpha = 0xFF;
return ret.full;
#else
lv_color32_t ret;
ret.ch.red = color.ch.red * 8; /*(2^8 - 1)/(2^5 - 1) = 255/31 = 8*/
ret.ch.green = ((color.ch.green_h << 3) + color.ch.green_l) * 4; /*(2^8 - 1)/(2^6 - 1) = 255/63 = 4*/
ret.ch.blue = color.ch.blue * 8; /*(2^8 - 1)/(2^5 - 1) = 255/31 = 8*/
ret.ch.red = ( color.ch.red * 263 + 7 ) >> 5;
#if LV_COLOR_16_SWAP == 0
ret.ch.green = ( color.ch.green * 259 + 3 ) >> 6;
#else
ret.ch.green = (((color.ch.green_h << 3) + color.ch.green_l) * 259 + 3 ) >> 6;
#endif
ret.ch.blue = ( color.ch.blue * 263 + 7 ) >> 5;
ret.ch.alpha = 0xFF;
return ret.full;
#endif
#elif LV_COLOR_DEPTH == 32
return color.full;
#endif