Rewrite tool png_dimensions.c, and start using common.h more

tools/png_dimensions.c

@@ -1,57 +1,25 @@
-#include <stdio.h>
-#include <stdint.h>
-#include <stdlib.h>
+#include "common.h"
 
-void usage(void) {
-	fprintf(stderr, "Usage: png_dimensions infile outfile\n");
-	exit(1);
+void usage() {
+	fprintf(stderr, "Usage: png_dimensions in.png out.dimensions\n");
 }
 
-void output_dimensions(char* png_filename, char* out_filename) {
-	FILE* f;
-	int width, height;
-	int i;
-	uint8_t bytes[4];
-	uint8_t output;
-
-	f = fopen(png_filename, "rb");
-	if (f == NULL) {
-		fprintf(stderr, "failed to open file %s\n", png_filename);
+uint8_t read_dimensions(const char *filename) {
+	uint32_t width_px = read_png_width_verbose(filename);
+	if (width_px != 40 && width_px != 48 && width_px != 56) {
+		fprintf(stderr, "Not a valid width for \"%s\": %" PRIu32 " px\n", filename, width_px);
 		exit(1);
 	}
-
-	// width
-	fseek(f, 16, SEEK_SET);
-	int size = fread(bytes, 1, 4, f);
-	fclose(f);
-	if (size != 4) {
-		fprintf(stderr, "failed to read at offset 0x10 in file %s\n", png_filename);
-		exit(1);
-	}
-
-	width = 0;
-	for (i = 0; i < 4; i++) {
-		width |= bytes[i] << (8 * (3 - i));
-	}
-	width >>= 3;
-	height = width;
-
-	output = width & 0xf;
-	output |= (height & 0xf) << 4;
-
-	f = fopen(out_filename, "wb");
-	if (f == NULL) {
-		fprintf(stderr, "failed to open file %s\n", out_filename);
-		exit(1);
-	}
-	fwrite(&output, 1, 1, f);
-	fclose(f);
+	uint8_t width_tiles = (uint8_t)(width_px / 8);
+	return (width_tiles << 4) | width_tiles;
 }
 
-int main(int argc, char* argv[]) {
+int main(int argc, char *argv[]) {
 	if (argc < 3) {
 		usage();
+		exit(1);
 	}
-	output_dimensions(argv[1], argv[2]);
+	uint8_t output_byte = read_dimensions(argv[1]);
+	write_u8(argv[2], &output_byte, 1);
 	return 0;
 }