/*
 * Copyright 2005, Stephan Aßmus <superstippi@gmx.de>.
 * Copyright 2008, Andrej Spielmann <andrej.spielmann@seh.ox.ac.uk>.
 * All rights reserved. Distributed under the terms of the MIT License.
 *
 * DrawingMode implementing B_OP_SUBTRACT on B_RGBA32.
 *
 */

#ifndef DRAWING_MODE_SUBTRACT_SUBPIX_H
#define DRAWING_MODE_SUBTRACT_SUBPIX_H

#include "DrawingMode.h"
#include "GlobalSubpixelSettings.h"

// BLEND_SUBTRACT_SUBPIX
#define BLEND_SUBTRACT_SUBPIX(d, r, g, b, a1, a2, a3) \
{ \
        pixel32 _p; \
        _p.data32 = *(uint32*)d; \
        uint8 rt = max_c(0, _p.data8[2] - (r)); \
        uint8 gt = max_c(0, _p.data8[1] - (g)); \
        uint8 bt = max_c(0, _p.data8[0] - (b)); \
        BLEND_SUBPIX(d, rt, gt, bt, a1, a2, a3); \
}


// blend_solid_hspan_subtract_subpix
void
blend_solid_hspan_subtract_subpix(int x, int y, unsigned len,
        const color_type& c, const uint8* covers, agg_buffer* buffer,
        const PatternHandler* pattern)
{
        uint8* p = buffer->row_ptr(y) + (x << 2);
        const int subpixelL = gSubpixelOrderingRGB ? 2 : 0;
        const int subpixelM = 1;
        const int subpixelR = gSubpixelOrderingRGB ? 0 : 2;
        do {
                rgb_color color = pattern->ColorAt(x, y);
                BLEND_SUBTRACT_SUBPIX(p, color.red, color.green, color.blue,
                        covers[subpixelL], covers[subpixelM], covers[subpixelR]);
                covers += 3;
                p += 4;
                x++;
                len -= 3;
        } while (len);
}

#endif // DRAWING_MODE_SUBTRACT_SUBPIX_H