add a readme

README.md

@@ -0,0 +1,9 @@
+# QOI for Allegro
+
+This is a simple liballeg plugin that gives Allegro the ability to decode QOI images, in both 24-bit and 32-bit formats.
+
+Some example images and a test program are provided. All of the code is in allegro_qoi.c. The header file declares only a single function `al_init_qoi()` which takes no parameters (same thing as `al_init_image_addon()`). Call it once when your program starts.
+
+If you want you can also just drop the `allegro_qoi.c` into your project and forward-declare it's init function once where it's used.
+
+This plugin does not handle saving QOI images yet.

allegro_qoi.c

@@ -14,6 +14,7 @@ extern "C" {
 
 ALLEGRO_BITMAP* _al_load_qoi_f(ALLEGRO_FILE* file, int flags) {
 	qoi_desc meta;
+	ALLEGRO_PIXEL_FORMAT fmt;
 	uint8_t* file_bytes = malloc(al_fsize(file));
 	memset(file_bytes, 0, al_fsize(file));
 	void* file_pos = file_bytes;
@@ -27,10 +28,15 @@ ALLEGRO_BITMAP* _al_load_qoi_f(ALLEGRO_FILE* file, int flags) {
 
 	int oldflags = al_get_new_bitmap_flags();
 	al_set_new_bitmap_flags(flags);
+	switch (meta.channels) {
+		case 3: fmt = ALLEGRO_PIXEL_FORMAT_BGR_888; break;
+		case 4: fmt = ALLEGRO_PIXEL_FORMAT_ABGR_8888; break;
+		default: free(data); return NULL; break;
+	}
 	ALLEGRO_BITMAP* bmp = al_create_bitmap(meta.width, meta.height);
 	ALLEGRO_LOCKED_REGION* lock = al_lock_bitmap(
 		bmp,
-		ALLEGRO_PIXEL_FORMAT_ABGR_8888,
+		fmt,
 		ALLEGRO_LOCK_WRITEONLY
 	);
 	al_set_new_bitmap_flags(oldflags);

sample.c

@@ -1,24 +1,30 @@
 // This program simply loads a QOI file into Allegro
 // as a texture and then dumps the texture data as a PNG.
-// Take notice of lines 20 and 21. You only need to initialize
+// Take notice of lines 26 and 27. You only need to initialize
 // the QOI plugin (this registers the function hooks that Allegro
 // will use whenever you want to I/O on a filename ending in .qoi)
 // 
-// Compile the test program with:
-// gcc -o test allegro_qoi.c test.c -lallegro -lallegro_image -I./
+// Compile the sample program with:
+// gcc -o sample allegro_qoi.c sample.c -lallegro -lallegro_image -I./
+// Then run it with a QOI image as the first argument.
 // 
 // qoi.h should be inside of your include path.
 // Either place it here, or in your system's global includes.
 
+#include <stdio.h>
 #include <allegro5/allegro.h>
 #include <allegro5/allegro_image.h>
 #include "allegro_qoi.h"
 
-int main() {
+int main(int argc, char **argv) {
+	if (argc < 2) {
+		printf("Usage: sample <filename>\n");
+		return 0;
+	}
 	al_init();
 	al_init_image_addon();
 	al_init_qoi();
-	ALLEGRO_BITMAP* bmp = al_load_bitmap("sample.qoi");
+	ALLEGRO_BITMAP* bmp = al_load_bitmap(argv[1]);
 	al_save_bitmap("out.png", bmp);
 	return 0;
 }