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71 lines
2.0 KiB
C
71 lines
2.0 KiB
C
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/*
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* \brief Interpolation functions for polygon painting
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* \date 2015-06-19
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* \author Norman Feske
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*/
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/*
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* Copyright (C) 2015 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__POLYGON_GFX__INTERPOLATE_RGBA_H_
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#define _INCLUDE__POLYGON_GFX__INTERPOLATE_RGBA_H_
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/* Genode includes */
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#include <util/color.h>
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namespace Polygon {
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using Genode::Color;
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template <typename PT>
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static inline void interpolate_rgba(Color, Color, PT *, unsigned char *,
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unsigned, int, int);
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}
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/**
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* Interpolate color values
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*/
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template <typename PT>
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static inline void Polygon::interpolate_rgba(Polygon::Color start,
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Polygon::Color end,
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PT *dst,
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unsigned char *dst_alpha,
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unsigned num_values,
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int x, int y)
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{
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/* sanity check */
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if (num_values == 0) return;
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/* use 16.16 fixpoint values for the calculation */
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int const r_ascent = ((end.r - start.r)<<16) / (int)num_values,
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g_ascent = ((end.g - start.g)<<16) / (int)num_values,
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b_ascent = ((end.b - start.b)<<16) / (int)num_values,
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a_ascent = ((end.a - start.a)<<16) / (int)num_values;
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/* set start values for color components */
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int r = start.r<<16,
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g = start.g<<16,
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b = start.b<<16,
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a = start.a<<16;
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for ( ; num_values--; dst++, dst_alpha++) {
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/* combine current color value with existing pixel via alpha blending */
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*dst = PT::mix(*dst, PT(r>>16, g>>16, b>>16), a>>16);
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*dst_alpha += ((255 - *dst_alpha)*a) >> (16 + 8);
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/* increment color-component values by ascent */
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r += r_ascent;
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g += g_ascent;
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b += b_ascent;
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a += a_ascent;
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}
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}
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#endif /* _INCLUDE__POLYGON_GFX__INTERPOLATE_RGBA_H_ */
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