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/* See LICENSE file for copyright and license details. */
#include "liblss16.h"
#include <string.h>
#if defined(__clang__)
# pragma clang diagnostic ignored "-Wunsafe-buffer-usage"
#endif
void
liblss16_optimise(struct liblss16_header *header, uint8_t *pixels)
{
uint8_t remap[16], unmap[16], ncolours = 0, colour, preferred, dummy = 0;
unsigned x, y, count, width;
size_t p, n;
int32_t zero[16], nonzero[16];
int32_t zero_penalty, least;
for (x = 0; x < 16U; x++) {
remap[x] = (uint8_t)x;
unmap[x] = 0;
}
memset(zero, 0, sizeof(zero));
memset(nonzero, 0, sizeof(nonzero));
for (x = 0; x < 15U; x++) {
if (unmap[x])
continue;
header->colour_map[ncolours++] = header->colour_map[x];
for (y = x + 1U; y < 16U; y++) {
if (header->colour_map[y].r != header->colour_map[x].r ||
header->colour_map[y].g != header->colour_map[x].g ||
header->colour_map[y].b != header->colour_map[x].b)
continue;
unmap[y] = 1;
remap[y] = ncolours;
}
}
width = (unsigned)header->width;
width = width < 17U ? width : 17U;
for (y = 0, p = 0; y < (unsigned)header->height; y++) {
#ifdef HARDEN
for (x = 0; x < (unsigned)header->width; x++)
pixels[p + x] &= 15U;
#endif
colour = remap[pixels[p]];
count = 1U;
for (x = 1U; x < width; x++, p++) {
if (remap[pixels[p]] != colour)
break;
count += 1U;
}
p += (size_t)header->width - (size_t)x;
zero[colour] += count < 16U ? 2 : 3;
nonzero[colour] += count == 1 ? 1 : count < 17 ? 3 : 4;
}
least = zero[0] - nonzero[0];
preferred = 0U;
if (ncolours < 16U)
dummy = ncolours++;
for (x = 1U; x < (unsigned)ncolours; x++) {
zero_penalty = zero[x] - nonzero[x];
if (zero_penalty < least) {
least = zero_penalty;
preferred = (uint8_t)x;
}
}
if (preferred) {
struct liblss16_colour tc;
uint8_t t8;
tc = header->colour_map[preferred];
header->colour_map[preferred] = header->colour_map[0];
header->colour_map[0] = tc;
t8 = remap[preferred];
remap[preferred] = remap[0];
remap[0] = t8;
if (preferred == dummy) {
header->colour_map[0].r = header->colour_map[1].r;
header->colour_map[0].g = header->colour_map[1].r;
header->colour_map[0].b = header->colour_map[1].r;
}
}
n = p;
for (n = p, p = 0; p < n; p++)
pixels[p] = remap[pixels[p]];
memset(&header->colour_map[ncolours],
header->colour_map[ncolours - 1U].b,
(16U - ncolours) * sizeof(*header->colour_map));
}
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