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pixblock-scaler.cpp

#define __NR_PIXBLOCK_SCALER_CPP__

/*
 * Functions for blitting pixblocks using scaling
 *
 * Author:
 *   Niko Kiirala <niko@kiirala.com>
 *
 * Copyright (C) 2006,2009 Niko Kiirala
 *
 * Released under GNU GPL, read the file 'COPYING' for more information
 */

#include <glib.h>
#include <cmath>
#if defined (SOLARIS) && (SOLARIS == 8)
#include "round.h"
using Inkscape::round;
#endif 
using std::floor;

#include "display/nr-filter-utils.h"
#include "libnr/nr-pixblock.h"
#include "libnr/nr-blit.h"
#include <2geom/forward.h>

namespace NR {

struct RGBA {
    double r, g, b, a;
};

/** Calculates cubically interpolated value of the four given pixel values.
 * The pixel values should be from four adjacent pixels in source image or
 * four adjacent interpolated values. len should be the x- or y-coordinate
 * (depending on interpolation direction) of the center of the target pixel
 * in source image coordinates.
 */
__attribute__ ((const))
inline static double sample(double const a, double const b,
                            double const c, double const d,
                            double const len)
{
    double lena = 1.5 + (len - round(len));
    double lenb = 0.5 + (len - round(len));
    double lenc = 0.5 - (len - round(len));
    double lend = 1.5 - (len - round(len));
    double const f = -0.5; // corresponds to cubic Hermite spline
    double sum = 0;
    sum += ((((f * lena) - 5.0 * f) * lena + 8.0 * f) * lena - 4 * f) * a;
    sum += (((f + 2.0) * lenb - (f + 3.0)) * lenb * lenb + 1.0) * b;
    sum += (((f + 2.0) * lenc - (f + 3.0)) * lenc * lenc + 1.0) * c;
    sum += ((((f * lend) - 5.0 * f) * lend + 8.0 * f) * lend - 4 * f) * d;

    return sum;
}

/**
 * Sanity check function for indexing pixblocks.
 * Catches reading and writing outside the pixblock area.
 * When enabled, decreases filter rendering speed massively.
 */
inline static void _check_index(NRPixBlock const * const pb, int const location, int const line)
{
    if(false) {
        int max_loc = pb->rs * (pb->area.y1 - pb->area.y0);
        if (location < 0 || (location + 4) > max_loc)
            g_warning("Location %d out of bounds (0 ... %d) at line %d", location, max_loc, line);
    }
}

static void scale_bicubic_rgba(NRPixBlock *to, NRPixBlock *from,
                               Geom::Matrix const &trans)
{
    if (NR_PIXBLOCK_BPP(from) != 4 || NR_PIXBLOCK_BPP(to) != 4) {
        g_warning("A non-32-bpp image passed to scale_bicubic_rgba: scaling aborted.");
        return;
    }

    bool free_from_on_exit = false;
    if (from->mode != to->mode){
        NRPixBlock *o_from = from;
        from = new NRPixBlock;
        nr_pixblock_setup_fast(from, to->mode, o_from->area.x0, o_from->area.y0, o_from->area.x1, o_from->area.y1, false);
        nr_blit_pixblock_pixblock(from, o_from);
        free_from_on_exit = true;
    }

    // Precalculate sizes of source and destination pixblocks
    int from_width = from->area.x1 - from->area.x0;
    int from_height = from->area.y1 - from->area.y0;
    int to_width = to->area.x1 - to->area.x0;
    int to_height = to->area.y1 - to->area.y0;

    // from_step: when advancing one pixel in destination image,
    // how much we should advance in source image
    double from_stepx = 1.0 / trans[0];
    double from_stepy = 1.0 / trans[3];
    double from_diffx = from_stepx * (-trans[4]);
    double from_diffy = from_stepy * (-trans[5]);
    from_diffx = (to->area.x0 * from_stepx + from_diffx) - from->area.x0;
    from_diffy = (to->area.y0 * from_stepy + from_diffy) - from->area.y0;

    // Loop through every pixel of destination image, a line at a time
    for (int to_y = 0 ; to_y < to_height ; to_y++) {
        double from_y = (to_y + 0.5) * from_stepy + from_diffy;
        // Pre-calculate beginning of the four horizontal lines, from
        // which we should read
        int from_line[4];
        for (int i = 0 ; i < 4 ; i++) {
            int fy_line = (int)round(from_y) + i - 2;
            if (fy_line >= 0) {
                if (fy_line < from_height) {
                    from_line[i] = fy_line * from->rs;
                } else {
                    from_line[i] = (from_height - 1) * from->rs;
                }
            } else {
                from_line[i] = 0;
            }
        }
        // Loop through this horizontal line in destination image
        // For every pixel, calculate the color of pixel with
        // bicubic interpolation and set the pixel value in destination image
        for (int to_x = 0 ; to_x < to_width ; to_x++) {
            double from_x = (to_x + 0.5) * from_stepx + from_diffx;
            RGBA line[4];
            for (int i = 0 ; i < 4 ; i++) {
                int k = (int)round(from_x) + i - 2;
                if (k < 0) k = 0;
                if (k >= from_width) k = from_width - 1;
                k *= 4;
                _check_index(from, from_line[0] + k, __LINE__);
                _check_index(from, from_line[1] + k, __LINE__);
                _check_index(from, from_line[2] + k, __LINE__);
                _check_index(from, from_line[3] + k, __LINE__);
                line[i].r = sample(NR_PIXBLOCK_PX(from)[from_line[0] + k],
                                   NR_PIXBLOCK_PX(from)[from_line[1] + k],
                                   NR_PIXBLOCK_PX(from)[from_line[2] + k],
                                   NR_PIXBLOCK_PX(from)[from_line[3] + k],
                                   from_y);
                line[i].g = sample(NR_PIXBLOCK_PX(from)[from_line[0] + k + 1],
                                   NR_PIXBLOCK_PX(from)[from_line[1] + k + 1],
                                   NR_PIXBLOCK_PX(from)[from_line[2] + k + 1],
                                   NR_PIXBLOCK_PX(from)[from_line[3] + k + 1],
                                   from_y);
                line[i].b = sample(NR_PIXBLOCK_PX(from)[from_line[0] + k + 2],
                                   NR_PIXBLOCK_PX(from)[from_line[1] + k + 2],
                                   NR_PIXBLOCK_PX(from)[from_line[2] + k + 2],
                                   NR_PIXBLOCK_PX(from)[from_line[3] + k + 2],
                                   from_y);
                line[i].a = sample(NR_PIXBLOCK_PX(from)[from_line[0] + k + 3],
                                   NR_PIXBLOCK_PX(from)[from_line[1] + k + 3],
                                   NR_PIXBLOCK_PX(from)[from_line[2] + k + 3],
                                   NR_PIXBLOCK_PX(from)[from_line[3] + k + 3],
                                   from_y);
            }
            RGBA result;
            result.r = round(sample(line[0].r, line[1].r, line[2].r, line[3].r,
                                    from_x));
            result.g = round(sample(line[0].g, line[1].g, line[2].g, line[3].g,
                                    from_x));
            result.b = round(sample(line[0].b, line[1].b, line[2].b, line[3].b,
                                    from_x));
            result.a = round(sample(line[0].a, line[1].a, line[2].a, line[3].a,
                                    from_x));

            _check_index(to, to_y * to->rs + to_x * 4, __LINE__);

            using Inkscape::Filters::clamp;
            using Inkscape::Filters::clamp_alpha;
            if (to->mode == NR_PIXBLOCK_MODE_R8G8B8A8P) {
                /* Clamp the colour channels to range from 0 to result.a to
                 * make sure, we don't exceed 100% per colour channel with
                 * images that have premultiplied alpha */

                int const alpha = clamp((int)result.a);

                NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4]
                    = clamp_alpha((int)result.r, alpha);
                NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 1]
                    = clamp_alpha((int)result.g, alpha);
                NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 2]
                    = clamp_alpha((int)result.b, alpha);
                NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 3] = alpha;
            } else {
                NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4]
                    = clamp((int)result.r);
                NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 1]
                    = clamp((int)result.g);
                NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 2]
                    = clamp((int)result.b);
                NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 3]
                    = clamp((int)result.a);
            }
        }
    }
    if (free_from_on_exit) {
        nr_pixblock_release(from);
        delete from;
    }

}

void scale_bicubic_alpha(NRPixBlock *to, NRPixBlock *from,
                         Geom::Matrix const &trans)
{
    if (NR_PIXBLOCK_BPP(from) != 1 || NR_PIXBLOCK_BPP(to) != 1) {
        g_warning("A non-8-bpp image passed to scale_bicubic_alpha: scaling aborted.");
        return;
    }

    // Precalculate sizes of source and destination pixblocks
    int from_width = from->area.x1 - from->area.x0;
    int from_height = from->area.y1 - from->area.y0;
    int to_width = to->area.x1 - to->area.x0;
    int to_height = to->area.y1 - to->area.y0;

    // from_step: when advancing one pixel in destination image,
    // how much we should advance in source image
    double from_stepx = 1.0 / trans[0];
    double from_stepy = 1.0 / trans[3];
    double from_diffx = from_stepx * (-trans[4]);
    double from_diffy = from_stepy * (-trans[5]);
    from_diffx = (to->area.x0 * from_stepx + from_diffx) - from->area.x0;
    from_diffy = (to->area.y0 * from_stepy + from_diffy) - from->area.y0;

    // Loop through every pixel of destination image, a line at a time
    for (int to_y = 0 ; to_y < to_height ; to_y++) {
        double from_y = (to_y + 0.5) * from_stepy - from_diffy;
        // Pre-calculate beginning of the four horizontal lines, from
        // which we should read
        int from_line[4];
        for (int i = 0 ; i < 4 ; i++) {
            int fy_line = (int)round(from_y) + i - 2;
            if (fy_line >= 0) {
                if (fy_line < from_height) {
                    from_line[i] = fy_line * from->rs;
                } else {
                    from_line[i] = (from_height - 1) * from->rs;
                }
            } else {
                from_line[i] = 0;
            }
        }
        // Loop through this horizontal line in destination image
        // For every pixel, calculate the color of pixel with
        // bicubic interpolation and set the pixel value in destination image
        for (int to_x = 0 ; to_x < to_width ; to_x++) {
            double from_x = (to_x + 0.5) * from_stepx - from_diffx;
            double line[4];
            for (int i = 0 ; i < 4 ; i++) {
                int k = (int)round(from_x) + i - 2;
                if (k < 0) k = 0;
                if (k >= from_width) k = from_width - 1;
                _check_index(from, from_line[0] + k, __LINE__);
                _check_index(from, from_line[1] + k, __LINE__);
                _check_index(from, from_line[2] + k, __LINE__);
                _check_index(from, from_line[3] + k, __LINE__);
                line[i] = sample(NR_PIXBLOCK_PX(from)[from_line[0] + k],
                                 NR_PIXBLOCK_PX(from)[from_line[1] + k],
                                 NR_PIXBLOCK_PX(from)[from_line[2] + k],
                                 NR_PIXBLOCK_PX(from)[from_line[3] + k],
                                 from_y);
            }
            int result;
            result = (int)round(sample(line[0], line[1], line[2], line[3],
                                       from_x));

            _check_index(to, to_y * to->rs + to_x, __LINE__);

            NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x]
                = Inkscape::Filters::clamp(result);
        }
    }
}

void scale_bicubic(NRPixBlock *to, NRPixBlock *from, Geom::Matrix const &trans)
{
    if (NR_PIXBLOCK_BPP(to) == 4 && NR_PIXBLOCK_BPP(from) == 4) {
        scale_bicubic_rgba(to, from, trans);
    } else if (NR_PIXBLOCK_BPP(to) == 1 && NR_PIXBLOCK_BPP(from) == 1) {
        scale_bicubic_alpha(to, from, trans);
    } else {
        g_warning("NR::scale_bicubic: unsupported bitdepths for scaling: to %d, from %d", NR_PIXBLOCK_BPP(to), NR_PIXBLOCK_BPP(from));
    }
}

} /* namespace NR */
/*
  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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