png.c

#include <stdio.h>
#include <stdlib.h>
#include <png.h>

#include "pes.h"

void output_png(struct pes *pes)
{
	int i;
	int width  = pes->max_x - pes->min_x + 1;
	int height = pes->max_y - pes->min_y + 1;
	int outw = 128, outh = 128;
	png_byte **rows;
	struct pes_block *block;
	png_structp png_ptr;
	png_infop info_ptr;

	rows = calloc(sizeof(*rows), outh);
	for (i = 0; i < outh; i++)
		rows[i] = calloc(sizeof(png_byte)*4, outw);

	block = pes->blocks;
	while (block) {
		struct color *c = block->color;
		struct stitch *stitch = block->stitch;
		int i;

		for (i = 0; i < block->nr_stitches; i++, stitch++) {
			int x = (stitch->x - pes->min_x) * outw / width;
			int y = (stitch->y - pes->min_y) * outh / height;
			png_byte *ptr = rows[y] + x*4;

			ptr[0] = c->r;
			ptr[1] = c->g;
			ptr[2] = c->b;
			ptr[3] = 255;
		}
		block = block->next;
	}

	png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
	info_ptr = png_create_info_struct(png_ptr);
	png_init_io(png_ptr, stdout);
	png_set_IHDR(png_ptr, info_ptr, outw, outh,
		8, PNG_COLOR_TYPE_RGBA, PNG_INTERLACE_NONE,
		PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);

	png_write_info(png_ptr, info_ptr);

	png_write_image(png_ptr, rows);
	png_write_end(png_ptr, NULL);
}