bannerpng.c - Extracts the icon from a DS(i) ROM to a PNG, see bannergif.py for a better extractor capable of extracting animated icons but in Python

bannerpng.c

/* This is free and unencumbered software released into the public domain.
 *
 * Anyone is free to copy, modify, publish, use, compile, sell, or
 * distribute this software, either in source code form or as a compiled
 * binary, for any purpose, commercial or non-commercial, and by any
 * means.
 *
 * In jurisdictions that recognize copyright laws, the author or authors
 * of this software dedicate any and all copyright interest in the
 * software to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and
 * successors. We intend this dedication to be an overt act of
 * relinquishment in perpetuity of all present and future rights to this
 * software under copyright law.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * For more information, please refer to <http://unlicense.org/>
 */

/* To build:
 * gcc bannerpng.c lodepng.c -o bannerpng
 * https://lodev.org/lodepng/
 */

#include "lodepng.h"

#include <math.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>

/**
 * @param input path to the DS ROM
 * @param output path to write to
 * @return true if successful
 */
bool bannergif(const char *input, const char *output) {
	FILE *rom = fopen(input, "rb");
	if(!rom)
		return false;
	
	// Seek to banner
	fseek(rom, 0x68, SEEK_SET);
	uint32_t bannerOfs;
	fread(&bannerOfs, sizeof(uint32_t), 1, rom);
	fseek(rom, bannerOfs, SEEK_SET);

	// Load banner data
	uint8_t palette[0x10][4]; // 16 colors RGBA
	uint8_t bitmap[32 * 32 * 4]; // 32×32 RGBA

	// Read palette
	fseek(rom, bannerOfs + 0x220, SEEK_SET);
	for(int i = 0; i < 0x10; i++) {
		uint16_t color;
		fread(&color, sizeof(uint16_t), 1, rom);
		palette[i][0] = lroundf((color & 0x1F) * 255.0f / 31.0f);
		palette[i][1] = lroundf(((color >> 5) & 0x1F) * 255.0f / 31.0f);
		palette[i][2] = lroundf(((color >> 10) & 0x1F) * 255.0f / 31.0f);
		palette[i][3] = i == 0 ? 0x00 : 0xFF;
	}

	// Read bitmap
	fseek(rom, bannerOfs + 0x20, SEEK_SET);
	for(int ty = 0; ty < 4; ty++) {
		for(int tx = 0; tx < 4; tx++) {
			for(int y = 0; y < 8; y++) {
				for(int x = 0; x < 4; x++) {
					uint8_t byte = fgetc(rom);
					memcpy(bitmap + ((ty * 8 + y) * 32 * 4) + (tx * 8 + x * 2) * 4, palette[byte & 0xF], 4);
					memcpy(bitmap + ((ty * 8 + y) * 32 * 4) + (tx * 8 + x * 2) * 4 + 4, palette[byte >> 4], 4);
				}
			}
		}
	}

	fclose(rom);

	lodepng_encode32_file(output, bitmap, 32, 32);

	return true;
}

int main(int argc, char **argv) {
	if(argc < 3) {
		printf("Usage: %s input.nds output.png\n", argv[0]);
		return 1;
	}

	bool success = bannergif(argv[1], argv[2]);

	return success ? 0 : 1;
}