/* resample.c/v0.1 - generic resampler for complexfractals
* ** by Pegasus Epsilon <pegasus@pimpninjas.org>
* ** Distribute Unmodified -- http://pegasus.pimpninjas.org/license
* **
* ** Changelog:
* ** 0.1 -- First version.
*/
#include <inttypes.h> /* uint8_t, uint32_t */
#include <stdio.h> /* printf() */
#include <stdlib.h> /* exit() */
#include <string.h> /* strcmp() */
#define CHANNELS 3
#define RED 0
#define GRN 1
#define BLU 2
typedef struct {
uint8_t c[CHANNELS];
} RGB24;
void usage (char *myself) {
printf("Usage: %s [-v] infile width factor outfile\n", myself);
exit(0);
}
void fail (const char *msg) { /* report function failures */
perror(msg);
exit(1);
}
/* runtime function swapping ftw */
int nothing (const char *f, ...) { return 0; }
int (*debug)(const char *f, ...) = ¬hing;
RGB24 downsample (size_t px_width, RGB24 **samples) {
struct {
uint32_t c[CHANNELS];
} mixer;
RGB24 *row, result;
size_t x, y, d = px_width * px_width;
mixer.c[RED] = mixer.c[GRN] = mixer.c[BLU] = 0;
for (y = 0; y < px_width; y++) {
row = samples[y];
for (x = 0; x < px_width; x++) {
mixer.c[RED] += row[x].c[RED];
mixer.c[GRN] += row[x].c[GRN];
mixer.c[BLU] += row[x].c[BLU];
}
}
result.c[RED] = (uint8_t)(mixer.c[RED] / d);
result.c[GRN] = (uint8_t)(mixer.c[GRN] / d);
result.c[BLU] = (uint8_t)(mixer.c[BLU] / d);
return result;
}
int main (int argc, char **argv) {
size_t ibuf_len, obuf_len;
size_t px_x, px_y, spx_y; /* pixel x, y, subpixel row */
size_t px_width, px_size; /* in subpixel samples */
size_t img_width; /* in pixels */
FILE *ifile, *ofile;
RGB24 *ibuf, *obuf, **samples;
/* enable debug output */
if (argc > 5 && !strcmp(argv[1], "-v"))
{ debug = &printf; argc--; argv++; }
/* make sure we have the right amount of arguments */
if (5 != argc) usage(argv[0]);
/* process args */
if (NULL == (ifile = fopen(argv[1], "r"))) fail(argv[1]);
img_width = (size_t)atoi(argv[2]);
px_width = (size_t)atoi(argv[3]);
if (NULL == (ofile = fopen(argv[4], "w"))) fail(argv[4]);
/* setup runtime constants */
px_size = px_width * px_width;
obuf_len = sizeof(RGB24) * img_width;
ibuf_len = obuf_len * px_size;
/* allocate memory */
ibuf = (RGB24 *)malloc(ibuf_len);
obuf = (RGB24 *)malloc(obuf_len);
samples = (RGB24 **)malloc(sizeof(RGB24 *) * px_size);
/* process infile */
for (px_y = 0; ; px_y++) { /* ever */
/* read a full line of supersampled pixels */
if (1 != fread(ibuf, ibuf_len, (size_t)1, ifile))
{ if (feof(ifile)) break; else fail(argv[1]); }
debug("\rresampling line %d...", px_y + 1);
fflush(stdout);
/* downsample the all the pixels */
for (px_x = 0; px_x < img_width; px_x++) {
/* set up offsets to the supersamples in this pixel */
for (spx_y = 0; spx_y < px_width; spx_y++)
samples[spx_y] = ibuf + (img_width * px_width * spx_y) + (px_width * px_x);
/* downsample it */
obuf[px_x] = downsample(px_width, samples);
}
/* write the downsampled line */
if (1 != fwrite(obuf, obuf_len, (size_t)1, ofile))
fail(argv[4]);
fflush(ofile);
}
debug("Done.\n");
return 0;
}