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pngresize.c
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pngresize.c
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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "pngreader.h"
#include "pngutil.h"
#include "pngcmd.h"
#include "pngresize.h"
#define paranoia_ceil(d) (uint32_t)d + ((uint32_t)d < d ? 1 : 0)
#define roundl(d) ((uint32_t)d + ((d - (uint32_t)d) >= 0.5 ? 1 : 0))
void png_resize_init(pngreader *info);
void png_resize_line(unsigned char *scanline, unsigned char *previous_scanline, uint32_t length, pngreader *info);
void png_resize_done(pngreader *info);
void png_resize(FILE* fin, FILE* fout, uint32_t width, uint32_t height, pngcallbacks* callbacks, void* extra2)
{
pngcallbacks null_callbacks = { NULL, NULL, NULL };
pngcallbacks reader_callbacks;
struct pngresize resize_info;
resize_info.width = width;
resize_info.height = height;
resize_info.line_count = 0;
if (width == 0 && height == 0)
png_die("unspecified_dimensions", NULL);
if (callbacks == NULL)
resize_info.callbacks = &null_callbacks;
else
resize_info.callbacks = callbacks;
reader_callbacks.completed_scanline = &png_resize_line;
reader_callbacks.read_header = &png_resize_init;
reader_callbacks.done = &png_resize_done;
if (resize_info.callbacks->completed_scanline == NULL)
resize_info.callbacks->completed_scanline = &png_write_scanline_raw;
png_read(fin, fout, &reader_callbacks, &resize_info, extra2);
}
void png_resize_init(pngreader* info)
{
struct pngresize *rinfo = info->extra1;
unsigned int i;
if (info->header->properties.colortype == COLOR_PALETTE)
png_die("palette_resizing_unsupported", NULL);
if (rinfo->width != 0 && rinfo->height != 0)
{
rinfo->fx = (float)info->header->width / (float)rinfo->width;
rinfo->fy = (float)info->header->height / (float)rinfo->height;
}
else if (rinfo->width != 0)
{
rinfo->fx = rinfo->fy = (float)info->header->width / (float)rinfo->width;
rinfo->height = roundl((float)(info->header->height / rinfo->fy));
}
else if (rinfo->height != 0)
{
rinfo->fx = rinfo->fy = (float)info->header->height / (float)rinfo->height;
rinfo->width = roundl((float)(info->header->width / rinfo->fy));
}
if (rinfo->fx < 1.0 || rinfo->fy < 1.0)
png_die("upscaling_unsupported", NULL);
rinfo->max_line_count = (unsigned int)rinfo->fy;
if (rinfo->fy > rinfo->max_line_count) rinfo->max_line_count++;
rinfo->scanlines = xmalloc(rinfo->max_line_count * sizeof(char*));
for (i = 0; i < rinfo->max_line_count; i++)
rinfo->scanlines[i] = xmalloc(rinfo->width * info->bpp * sizeof(char));
rinfo->line_count = 0;
rinfo->written_lines = 0;
rinfo->last_line = calloc(rinfo->width * info->bpp, sizeof(char));
if (!rinfo->last_line) png_die("insufficient_memory", NULL);
if (rinfo->callbacks->read_header != NULL)
(*rinfo->callbacks->read_header)(info);
}
void png_resize_line(unsigned char *scanline, unsigned char *previous_scanline,
uint32_t length, pngreader *info)
{
struct pngresize *rinfo = info->extra1;
uint32_t i, j, k, start, end;
float divisor;
if (rinfo->line_count >= rinfo->max_line_count)
png_die("line_count_exceeds_max", NULL);
for (i = 0; i < rinfo->width; i++)
{
unsigned char pixel;
// TODO: Check whether ceil() is suitable
start = paranoia_ceil(rinfo->fx * i);
end = paranoia_ceil(rinfo->fx * (i + 1));
divisor = (float)(end - start);
for (j = 0; j < info->bpp; j++)
{
pixel = 0;
for (k = 0; k < end - start; k++)
pixel += (unsigned char)(scanline[(start + k) * info->bpp + j] / divisor);
rinfo->scanlines[rinfo->line_count][i * info->bpp + j] = pixel;
}
}
rinfo->line_count++;
if ((info->line_count / rinfo->fy) > (rinfo->written_lines + 1))
{
unsigned char *scanline = calloc(rinfo->width, info->bpp);
if (!scanline) png_die("insufficient_memory", NULL);
for (i = 0; i < rinfo->width * info->bpp; i++)
{
for (j = 0; j < rinfo->line_count; j++)
scanline[i] += rinfo->scanlines[j][i] / rinfo->line_count;
}
rinfo->line_count = 0;
(*rinfo->callbacks->completed_scanline)(scanline,
rinfo->last_line, rinfo->width * info->bpp, info);
free(rinfo->last_line);
rinfo->last_line = scanline;
rinfo->written_lines++;
}
}
void png_resize_done(pngreader* info)
{
unsigned int i;
struct pngresize* rinfo = info->extra1;
while (rinfo->written_lines < rinfo->height)
{
(*rinfo->callbacks->completed_scanline)(
rinfo->last_line, rinfo->last_line,
rinfo->width * info->bpp, info);
rinfo->written_lines++;
}
if (rinfo->callbacks->done != NULL)
(*rinfo->callbacks->done)(info);
for (i=0; i < rinfo->max_line_count; i++)
free(rinfo->scanlines[i]);
free(rinfo->scanlines);
free(rinfo->last_line);
}
#ifdef PNGRESIZE
int main(int argc, char **argv)
{
FILE *in, *out;
struct pngopts opts;
pngcmd_getopts(&opts, argc, argv);
png_open_streams(&opts, &in, &out);
png_resize(in, out, opts.width, opts.height, NULL, NULL);
fclose(in); fclose(out);
return 0;
}
#endif