stb.c

#define STB_IMAGE_IMPLEMENTATION
#define STB_IMAGE_WRITE_IMPLEMENTATION
#define STBI_ONLY_PNG
#define STBI_ONLY_JPEG
#define STBI_ONLY_BMP
#define STBI_ONLY_GIF

#include "stb_image.h"
#include "stb_image_write.h"

#ifdef __cplusplus
extern "C" {
#endif

typedef struct gif_result_t {
	int delay;
	unsigned char *data;
	struct gif_result_t *next;
} gif_result;

STBIDEF unsigned char *stbi_xload(char const *filename, int *x, int *y, int *frames)
{
	FILE *f;
	stbi__context s;
	unsigned char *result = 0;

	if (!(f = stbi__fopen(filename, "rb")))
		return stbi__errpuc("can't fopen", "Unable to open file");

	stbi__start_file(&s, f);

	if (stbi__gif_test(&s))
	{
		int c;
		stbi__gif g;
		gif_result head;
		gif_result *prev = 0, *gr = &head;

		memset(&g, 0, sizeof(g));
		memset(&head, 0, sizeof(head));

		*frames = 0;

		while (gr->data = stbi__gif_load_next(&s, &g, &c, 4))
		{
			if (gr->data == (unsigned char*)&s)
			{
				gr->data = 0;
				break;
			}

			if (prev) prev->next = gr;
			gr->delay = g.delay;
			prev = gr;
			gr = (gif_result*) stbi__malloc(sizeof(gif_result));
			memset(gr, 0, sizeof(gif_result));
			++(*frames);
		}

		STBI_FREE(g.out);

		if (gr != &head)
			STBI_FREE(gr);

		if (*frames > 0)
		{
			*x = g.w;
			*y = g.h;
		}

		result = head.data;

		if (*frames > 1)
		{
			unsigned int size = 4 * g.w * g.h;
			unsigned char *p = 0;

			result = (unsigned char*)stbi__malloc(*frames * (size + 2));
			gr = &head;
			p = result;

			while (gr)
			{
				prev = gr;
				memcpy(p, gr->data, size);
				p += size;
				*p++ = gr->delay & 0xFF;
				*p++ = (gr->delay & 0xFF00) >> 8;
				gr = gr->next;

				STBI_FREE(prev->data);
				if (prev != &head) STBI_FREE(prev);
			}
		}
	}
	else
	{
		result = stbi__load_main(&s, x, y, frames, 4);
		*frames = !!result;
	}

	fclose(f);
	return result;
}

#ifdef __cplusplus
}
#endif

Nevermind this was my mistake.

This is how you allow vertical flipping for the gifs :)

Hey @Platforming-Mayhem, looks like you got it working, good to know!

By the way, that last line you're highlighting looks suspicious to me. Isn't stbi_set_flip_vertically_on_load a function? My C/C++ is rusty but I think that might be interpreting it as a pointer and just testing that it's not zero, so stbi__vertical_flip_slices is always called.

@urraka I'm not sure, since I just copied it from one of the stb_load functions

@Platforming-Mayhem nevermind what I said, my bad. The function is stbi_set_flip_vertically_on_load but you have stbi__vertically_flip_on_load so it's all good ;D

Hi @urraka,
I've been using this code for a while now but recently I found out that it takes up a lot of memory. Is this normal and is there anyway to decrease the amount of memory that is used?
Thanks :)

Hi @Platforming-Mayhem. The way this works is the easy way out: load every frame into memory in RGBA format. If you have big images with many frames it will take a lot of memory (width * height * 4 * number of frames bytes). I suppose, in theory, one could load the compressed file into memory and buffer a few frames at a time (sort of like video preloading)... but that would need a lot more work.

Thanks :)
This was a big help :D