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nr-filter-blend.cpp

/*
 * SVG feBlend renderer
 *
 * "This filter composites two objects together using commonly used
 * imaging software blending modes. It performs a pixel-wise combination
 * of two input images." 
 * http://www.w3.org/TR/SVG11/filters.html#feBlend
 *
 * Authors:
 *   Niko Kiirala <niko@kiirala.com>
 *   Jasper van de Gronde <th.v.d.gronde@hccnet.nl>
 *
 * Copyright (C) 2007-2008 authors
 *
 * Released under GNU GPL, read the file 'COPYING' for more information
 */

#include "display/nr-filter-blend.h"
#include "display/nr-filter-pixops.h"
#include "display/nr-filter-primitive.h"
#include "display/nr-filter-slot.h"
#include "display/nr-filter-types.h"
#include "display/nr-filter-units.h"
#include "libnr/nr-pixblock.h"
#include "libnr/nr-blit.h"
#include "libnr/nr-pixops.h"

namespace Inkscape {
namespace Filters {

/*
 * From http://www.w3.org/TR/SVG11/filters.html#feBlend
 *
 * For all feBlend modes, the result opacity is computed as follows:
 * qr = 1 - (1-qa)*(1-qb)
 *
 * For the compositing formulas below, the following definitions apply:
 * cr = Result color (RGB) - premultiplied
 * qa = Opacity value at a given pixel for image A
 * qb = Opacity value at a given pixel for image B
 * ca = Color (RGB) at a given pixel for image A - premultiplied
 * cb = Color (RGB) at a given pixel for image B - premultiplied
 */

/*
 * These blending equations given in SVG standard are for color values
 * in the range 0..1. As these values are stored as unsigned char values,
 * they need some reworking. An unsigned char value can be thought as
 * 0.8 fixed point representation of color value. This is how I've
 * ended up with these equations here.
 */

// Set alpha / opacity. This line is same for all the blending modes,
// so let's save some copy-pasting.
#define SET_ALPHA r[3] = NR_NORMALIZE_21((255 * 255) - (255 - a[3]) * (255 - b[3]))

// cr = (1 - qa) * cb + ca
inline void
blend_normal(unsigned char *r, unsigned char const *a, unsigned char const *b)
{
    r[0] = NR_COMPOSEPPP_1111(a[0],a[3],b[0]);
    r[1] = NR_COMPOSEPPP_1111(a[1],a[3],b[1]);
    r[2] = NR_COMPOSEPPP_1111(a[2],a[3],b[2]);
    SET_ALPHA;
}

// cr = (1-qa)*cb + (1-qb)*ca + ca*cb
inline void
blend_multiply(unsigned char *r, unsigned char const *a, unsigned char const *b)
{
    r[0] = NR_NORMALIZE_21((255 - a[3]) * b[0] + (255 - b[3]) * a[0]
                           + a[0] * b[0]);
    r[1] = NR_NORMALIZE_21((255 - a[3]) * b[1] + (255 - b[3]) * a[1]
                           + a[1] * b[1]);
    r[2] = NR_NORMALIZE_21((255 - a[3]) * b[2] + (255 - b[3]) * a[2]
                           + a[2] * b[2]);
    SET_ALPHA;
}

// cr = cb + ca - ca * cb
inline void
blend_screen(unsigned char *r, unsigned char const *a, unsigned char const *b)
{
    r[0] = NR_NORMALIZE_21((b[0] + a[0]) * 255 - a[0] * b[0]);
    r[1] = NR_NORMALIZE_21((b[1] + a[1]) * 255 - a[1] * b[1]);
    r[2] = NR_NORMALIZE_21((b[2] + a[2]) * 255 - a[2] * b[2]);
    SET_ALPHA;
}

// cr = Min ((1 - qa) * cb + ca, (1 - qb) * ca + cb)
inline void
blend_darken(unsigned char *r, unsigned char const *a, unsigned char const *b)
{
    r[0] = NR_NORMALIZE_21(std::min(NR_COMPOSEPPP_1112(a[0],a[3],b[0]),
                                    NR_COMPOSEPPP_1112(b[0],b[3],a[0])));
    r[1] = NR_NORMALIZE_21(std::min(NR_COMPOSEPPP_1112(a[1],a[3],b[1]),
                                    NR_COMPOSEPPP_1112(b[1],b[3],a[1])));
    r[2] = NR_NORMALIZE_21(std::min(NR_COMPOSEPPP_1112(a[2],a[3],b[2]),
                                    NR_COMPOSEPPP_1112(b[2],b[3],a[2])));
    SET_ALPHA;
}

// cr = Max ((1 - qa) * cb + ca, (1 - qb) * ca + cb)
inline void
blend_lighten(unsigned char *r, unsigned char const *a, unsigned char const *b)
{
    r[0] = NR_NORMALIZE_21(std::max(NR_COMPOSEPPP_1112(a[0],a[3],b[0]),
                                    NR_COMPOSEPPP_1112(b[0],b[3],a[0])));
    r[1] = NR_NORMALIZE_21(std::max(NR_COMPOSEPPP_1112(a[1],a[3],b[1]),
                                    NR_COMPOSEPPP_1112(b[1],b[3],a[1])));
    r[2] = NR_NORMALIZE_21(std::max(NR_COMPOSEPPP_1112(a[2],a[3],b[2]),
                                    NR_COMPOSEPPP_1112(b[2],b[3],a[2])));
    SET_ALPHA;
}

FilterBlend::FilterBlend() 
    : _blend_mode(BLEND_NORMAL),
      _input2(NR_FILTER_SLOT_NOT_SET)
{}

FilterPrimitive * FilterBlend::create() {
    return new FilterBlend();
}

FilterBlend::~FilterBlend()
{}

int FilterBlend::render(FilterSlot &slot, FilterUnits const & /*units*/) {
    NRPixBlock *in1 = slot.get(_input);
    NRPixBlock *in2 = slot.get(_input2);
    NRPixBlock *original_in1 = in1;
    NRPixBlock *original_in2 = in2;
    NRPixBlock *out;

    // Bail out if either one of source images is missing
    if (!in1 || !in2) {
        g_warning("Missing source image for feBlend (in=%d in2=%d)", _input, _input2);
        return 1;
    }

    out = new NRPixBlock;
    NRRectL out_area;
    nr_rect_l_union(&out_area, &in1->area, &in2->area);
    nr_pixblock_setup_fast(out, NR_PIXBLOCK_MODE_R8G8B8A8P,
                           out_area.x0, out_area.y0, out_area.x1, out_area.y1,
                           true);

    // Blending modes are defined for premultiplied RGBA values,
    // thus convert them to that format before blending
    if (in1->mode != NR_PIXBLOCK_MODE_R8G8B8A8P) {
        in1 = new NRPixBlock;
        nr_pixblock_setup_fast(in1, NR_PIXBLOCK_MODE_R8G8B8A8P,
                               original_in1->area.x0, original_in1->area.y0,
                               original_in1->area.x1, original_in1->area.y1,
                               false);
        nr_blit_pixblock_pixblock(in1, original_in1);
    }
    if (in2->mode != NR_PIXBLOCK_MODE_R8G8B8A8P) {
        in2 = new NRPixBlock;
        nr_pixblock_setup_fast(in2, NR_PIXBLOCK_MODE_R8G8B8A8P,
                               original_in2->area.x0, original_in2->area.y0,
                               original_in2->area.x1, original_in2->area.y1,
                               false);
        nr_blit_pixblock_pixblock(in2, original_in2);
    }

    /* pixops_mix is defined in display/nr-filter-pixops.h
     * It mixes the two input images with the function given as template
     * and places the result in output image.
     */
    switch (_blend_mode) {
        case BLEND_MULTIPLY:
            pixops_mix<blend_multiply>(*out, *in1, *in2);
            break;
        case BLEND_SCREEN:
            pixops_mix<blend_screen>(*out, *in1, *in2);
            break;
        case BLEND_DARKEN:
            pixops_mix<blend_darken>(*out, *in1, *in2);
            break;
        case BLEND_LIGHTEN:
            pixops_mix<blend_lighten>(*out, *in1, *in2);
            break;
        case BLEND_NORMAL:
        default:
            pixops_mix<blend_normal>(*out, *in1, *in2);
            break;
    }

    if (in1 != original_in1) {
        nr_pixblock_release(in1);
        delete in1;
    }
    if (in2 != original_in2) {
        nr_pixblock_release(in2);
        delete in2;
    }

    out->empty = FALSE;
    slot.set(_output, out);

    return 0;
}

void FilterBlend::set_input(int slot) {
    _input = slot;
}

void FilterBlend::set_input(int input, int slot) {
    if (input == 0) _input = slot;
    if (input == 1) _input2 = slot;
}

void FilterBlend::set_mode(FilterBlendMode mode) {
    if (mode == BLEND_NORMAL || mode == BLEND_MULTIPLY ||
        mode == BLEND_SCREEN || mode == BLEND_DARKEN ||
        mode == BLEND_LIGHTEN)
    {
        _blend_mode = mode;
    }
}

} /* namespace Filters */
} /* namespace Inkscape */

/*
  Local Variables:
  mode:c++
  c-file-style:"stroustrup"
  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
  indent-tabs-mode:nil
  fill-column:99
  End:
*/
// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :

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