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C script which prints x, y, and y_offset fields of sprite coordinates
#include <stdio.h>
#include <png.h>
#include <stdlib.h>
#define FATAL_ERROR(...) ({fprintf(stderr, __VA_ARGS__);exit(1);})
#define min(a, b) ((a) < (b) ? (a) : (b))
struct Image
{
unsigned width;
unsigned height;
unsigned char * pixels;
unsigned char bitDepth;
unsigned char pixelsPerByte;
unsigned char mask;
};
static int image_get_pixel(struct Image const * image, int x, int y) {
int pixelOffset = y * image->width + x;
int pixel = image->pixels[pixelOffset / image->pixelsPerByte];
pixel >>= image->bitDepth * (pixelOffset % image->pixelsPerByte);
return pixel & image->mask;
}
static int get_left_margin(struct Image const * image) {
int maxw = image->width / 2;
for (int x = 0; x < maxw; x++) {
for (int y = 0; y < image->height; y++) {
if (image_get_pixel(image, x, y)) return x;
}
}
return maxw;
}
static int get_right_margin(struct Image const * image) {
int maxw = image->width / 2;
for (int x = 0; x < maxw; x++) {
for (int y = 0; y < image->height; y++) {
if (image_get_pixel(image, image->width - x - 1, y)) return x;
}
}
return maxw;
}
static int get_top_margin(struct Image const * image) {
int maxh = image->height / 2;
for (int y = 0; y < maxh; y++) {
for (int x = 0; x < image->width; x++) {
if (image_get_pixel(image, x, y)) return y;
}
}
return maxh;
}
static int get_bottom_margin(struct Image const * image) {
int maxh = image->height / 2;
for (int y = 0; y < maxh; y++) {
for (int x = 0; x < image->width; x++) {
if (image_get_pixel(image, x, image->height - y - 1)) return y;
}
}
return maxh;
}
static void read_png(const char * path, struct Image * image) {
png_structp png_ptr;
png_infop info_ptr;
FILE *fp = fopen(path, "rb");
unsigned char sig[8];
if (fp == NULL)
FATAL_ERROR("Failed to open \"%s\" for reading.\n", path);
if (fread(sig, sizeof(unsigned char), 8, fp) != 8)
FATAL_ERROR("Failed to read PNG signature from \"%s\".\n", path);
if (png_sig_cmp(sig, 0, 8))
FATAL_ERROR("\"%s\" does not have a valid PNG signature.\n", path);
png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if (!png_ptr)
FATAL_ERROR("Failed to create PNG read struct.\n");
info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr)
FATAL_ERROR("Failed to create PNG info struct.\n");
if (setjmp(png_jmpbuf(png_ptr)))
FATAL_ERROR("Failed to init I/O for reading \"%s\".\n", path);
png_init_io(png_ptr, fp);
png_set_sig_bytes(png_ptr, 8);
png_read_info(png_ptr, info_ptr);
image->width = png_get_image_width(png_ptr, info_ptr);
image->height = png_get_image_height(png_ptr, info_ptr);
image->bitDepth = png_get_bit_depth(png_ptr, info_ptr);
if (image->bitDepth != 1 && image->bitDepth != 2 && image->bitDepth != 4 && image->bitDepth != 8)
FATAL_ERROR("Bit depth of image must be 1, 2, 4, or 8.");
unsigned rowbytes = png_get_rowbytes(png_ptr, info_ptr);
image->mask = (1 << image->bitDepth) - 1;
image->pixelsPerByte = 8 / image->bitDepth;
image->pixels = malloc(image->height * rowbytes);
if (image->pixels == NULL)
FATAL_ERROR("Failed to allocate pixel buffer.\n");
png_bytepp row_pointers = malloc(image->height * sizeof(png_bytep));
if (row_pointers == NULL)
FATAL_ERROR("Failed to allocate row pointers.\n");
for (int i = 0; i < image->height; i++)
row_pointers[i] = (png_bytep)(image->pixels + (i * rowbytes));
if (setjmp(png_jmpbuf(png_ptr)))
FATAL_ERROR("Error reading from \"%s\".\n", path);
png_read_image(png_ptr, row_pointers);
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
fclose(fp);
free(row_pointers);
}
static void get_sprite_coords(const char * path, int *width, int *height, int *bottom) {
struct Image image = {};
read_png(path, &image);
int left = get_left_margin(&image);
int right = get_right_margin(&image);
int top = get_top_margin(&image);
*bottom = get_bottom_margin(&image);
*width = image.width / 8 - min(left, right) / 4;
*height = image.height / 8 - min(top, *bottom) / 4;
free(image.pixels);
}
int main(int argc, char ** argv) {
for (int i = 1; i < argc; i++) {
int width, height, bottom;
get_sprite_coords(argv[i], &width, &height, &bottom);
printf("%s %d %d %d\n", argv[i], width, height, bottom);
}
return 0;
}
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