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gems: reset 'Nitpicker_buffer' to gray, not black

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This improves the output quality of antialiased lines onto a transparent
nitpicker buffer. For antialiased graphics operations, the initial color
leaks through. Leaking 50% gray is better than leaking black, in
particular when drawing white lines.
This commit is contained in:
Norman Feske 2017-08-18 08:23:13 +02:00 committed by Christian Helmuth
parent c3d3815476
commit 29c6d9ee9d
1 changed files with 17 additions and 2 deletions
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19
repos/gems/include/gems/nitpicker_buffer.h
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@ -90,7 +90,9 @@ struct Nitpicker_buffer
ram(ram), rm(rm), nitpicker(nitpicker), ram(ram), rm(rm), nitpicker(nitpicker),
mode(Genode::max(1UL, size.w()), Genode::max(1UL, size.h()), mode(Genode::max(1UL, size.w()), Genode::max(1UL, size.h()),
nitpicker.mode().format()) nitpicker.mode().format())
{ } {
reset_surface();
}
/** /**
* Constructor * Constructor
@ -131,7 +133,20 @@ struct Nitpicker_buffer
{ {
Genode::size_t const num_pixels = pixel_surface().size().count(); Genode::size_t const num_pixels = pixel_surface().size().count();
Genode::memset(alpha_surface().addr(), 0, num_pixels); Genode::memset(alpha_surface().addr(), 0, num_pixels);
Genode::memset(pixel_surface().addr(), 0, num_pixels*sizeof(Pixel_rgb888));
/*
* Initialize color buffer with 50% gray
*
* We do not use black to limit the bleeding of black into antialiased
* drawing operations applied onto an initially transparent background.
*/
Pixel_surface pixels = pixel_surface();
Pixel_rgb888 *dst = pixels.addr();
Pixel_rgb888 const gray(127, 127, 127, 255);
for (unsigned n = pixels.size().count(); n; n--)
*dst++ = gray;
} }
template <typename DST_PT, typename SRC_PT> template <typename DST_PT, typename SRC_PT>