/*
 * Copyright (c) 2009  M Joonas Pihlaja
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

/* Reference implementation using divisions.  Since the slow path is
 * so very slow this version specialises runs of constant or solid
 * pixels. */
#include <stddef.h>
#include <stdint.h>

/* Pixel format config for a 32 bit pixel with 8 bit components.  Only
 * the location of alpha matters. */
#ifndef ASHIFT
# define ASHIFT 24
#endif
#define RSHIFT ((24 + ASHIFT) % 32)
#define GSHIFT ((16 + ASHIFT) % 32)
#define BSHIFT (( 8 + ASHIFT) % 32)

#define AMASK (255 << ASHIFT)
#define RMASK (255 << RSHIFT)
#define GMASK (255 << GSHIFT)
#define BMASK (255 << BSHIFT)

void
unpremultiply_with_div(
    uint32_t * restrict       dst,
    uint32_t const * restrict src,
    size_t                    n)
{
    size_t i;
    
    for (i=0; i<n; i++) {
	uint32_t rgba = src[i];
	if (rgba & AMASK) {
	    uint32_t a = (rgba >> ASHIFT) & 0xFF;
	    uint32_t r = (rgba >> RSHIFT) & 0xFF;
	    uint32_t g = (rgba >> GSHIFT) & 0xFF;
	    uint32_t b = (rgba >> BSHIFT) & 0xFF;
	    r = r*255 / a;
	    g = g*255 / a;
	    b = b*255 / a;
	    dst[i] = (r<<RSHIFT) | (g<<GSHIFT) | (b<<BSHIFT) | (a << ASHIFT);
	} else {
	    dst[i] = 0;
	}
    }
}