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fix an alpha blend algorithm issue

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This commit is contained in:
Jinhao 2016-04-23 03:15:11 +08:00
parent c512b2dad5
commit 79f484dd2e
1 changed files with 6 additions and 4 deletions
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10
include/nana/paint/detail/image_processor.hpp
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@ -330,19 +330,21 @@ namespace detail
} }
const pixel_argb_t * s_end = s_rgb + rest; const pixel_argb_t * s_end = s_rgb + rest;
auto rest_d_rgb = d_rgb;
for(auto i = s_rgb; i != s_end; ++i) for(auto i = s_rgb; i != s_end; ++i)
{ {
if(i->element.alpha_channel) if(i->element.alpha_channel)
{ {
if(i->element.alpha_channel != 255) if(i->element.alpha_channel != 255)
{ {
d_rgb[3].element.red = unsigned(d_rgb[3].element.red * (255 - i->element.alpha_channel) + i->element.red * i->element.alpha_channel) / 255; rest_d_rgb->element.red = unsigned(rest_d_rgb->element.red * (255 - i->element.alpha_channel) + i->element.red * i->element.alpha_channel) / 255;
d_rgb[3].element.green = unsigned(d_rgb[3].element.green * (255 - i->element.alpha_channel) + i->element.green * i->element.alpha_channel) / 255; rest_d_rgb->element.green = unsigned(rest_d_rgb->element.green * (255 - i->element.alpha_channel) + i->element.green * i->element.alpha_channel) / 255;
d_rgb[3].element.blue = unsigned(d_rgb[3].element.blue * (255 - i->element.alpha_channel) + i->element.blue * i->element.alpha_channel) / 255; rest_d_rgb->element.blue = unsigned(rest_d_rgb->element.blue * (255 - i->element.alpha_channel) + i->element.blue * i->element.alpha_channel) / 255;
} }
else else
d_rgb[3] = *i; *rest_d_rgb = *i;
} }
++rest_d_rgb;
} }
d_rgb = pixel_at(d_rgb, d_step_bytes); d_rgb = pixel_at(d_rgb, d_step_bytes);
s_rgb = pixel_at(s_rgb, s_step_bytes); s_rgb = pixel_at(s_rgb, s_step_bytes);