genode/repos/gems/include/polygon_gfx/interpolate_rgb565.h
2017-02-28 12:59:29 +01:00

77 lines
2.2 KiB
C++

/*
* \brief RGB565-optimized interpolation functions for polygon painting
* \date 2015-06-19
* \author Norman Feske
*/
/*
* Copyright (C) 2015-2017 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
*/
#ifndef _INCLUDE__POLYGON_GFX__INTERPOLATE_RGB565_H_
#define _INCLUDE__POLYGON_GFX__INTERPOLATE_RGB565_H_
/* Genode includes */
#include <util/dither_matrix.h>
#include <os/pixel_rgb565.h>
#include <polygon_gfx/interpolate_rgba.h>
namespace Polygon {
using Genode::Pixel_rgb565;
template <>
inline void interpolate_rgba(Color, Color, Pixel_rgb565 *,
unsigned char *, unsigned, int, int);
}
/**
* Specialization that employs dithering
*/
template <>
inline void Polygon::interpolate_rgba(Color start, Color end, Pixel_rgb565 *dst,
unsigned char *dst_alpha,
unsigned num_values, int x, int y)
{
/* sanity check */
if (num_values <= 0) return;
/* use 16.16 fixpoint values for the calculation */
int r_ascent = ((end.r - start.r)<<16) / (int)num_values,
g_ascent = ((end.g - start.g)<<16) / (int)num_values,
b_ascent = ((end.b - start.b)<<16) / (int)num_values,
a_ascent = ((end.a - start.a)<<16) / (int)num_values;
/* set start values for color components */
int r = start.r<<16,
g = start.g<<16,
b = start.b<<16,
a = start.a<<16;
for ( ; num_values--; dst++, dst_alpha++, x++) {
int const dither_value = Genode::Dither_matrix::value(x, y) << 12;
/* combine current color value with existing pixel via alpha blending */
*dst = Pixel_rgb565::mix(*dst,
Pixel_rgb565((r + dither_value) >> 16,
(g + dither_value) >> 16,
(b + dither_value) >> 16),
(a + dither_value) >> 16);
*dst_alpha += ((255 - *dst_alpha)*(a + dither_value)) >> (16 + 8);
/* increment color-component values by ascent */
r += r_ascent;
g += g_ascent;
b += b_ascent;
a += a_ascent;
}
}
#endif /* _INCLUDE__POLYGON_GFX__INTERPOLATE_RGB565_H_ */