bgfx/3rdparty/iqa/source/decimate.c

/*
 * Copyright (c) 2011, Tom Distler (http://tdistler.com)
 * All rights reserved.
 *
 * The BSD License
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice, 
 *   this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 * - Neither the name of the tdistler.com nor the names of its contributors may
 *   be used to endorse or promote products derived from this software without
 *   specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "decimate.h"
#include <stdlib.h>

int _iqa_decimate(float *img, int w, int h, int factor, const struct _kernel *k, float *result, int *rw, int *rh)
{
    int x,y;
    int sw = w/factor + (w&1);
    int sh = h/factor + (h&1);
    int dst_offset;
    float *dst=img;

    if (result)
        dst = result;

    /* Downsample */
    for (y=0; y<sh; ++y) {
        dst_offset = y*sw;
        for (x=0; x<sw; ++x,++dst_offset) {
            dst[dst_offset] = _iqa_filter_pixel(img, w, h, x*factor, y*factor, k, 1.0f);
        }
    }
    
    if (rw) *rw = sw;
    if (rh) *rh = sh;
    return 0;
}