glgif

What is it?

glgif is a comprehensive library for playing back .gif animations on the iPhone using OpenGLES.

Sounds great, how do i use it?

At the core, glgif merely uploads frames from a gif animation to an OpenGLES texture. So all you need to do is the following:

// Load the gif
FILE *fp = fopen("test.gif", "r");
VideoSource *src = VideoSource_init(fp, VIDEOSOURCE_FILE);

// Init video using VideoSource
GifVideo *vid = [[GifVideo alloc] initWithSource:src inContext:[yourGLESContext]];
VideoSource_release(src);

// Set up the disposal texture
[vid setupRenderTexture];

// Setup our OpenGL context (viewFramebuffer is the frame buffer, backingWidth & backingHeight is the framebuffer size)
GLfloat projectionMatrix[16];
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrthof(0, backingWidth, 0, backingHeight, -1, 1);
glGetFloatv(GL_PROJECTION_MATRIX, projectionMatrix);

// Tell the gif renderer where we are rendering to
vid.viewRenderInfo = TargetRenderInfoMake(viewFramebuffer, GIFRectMake(0, 0, backingWidth, backingHeight), projectionMatrix);

// Then every frame...
[vid drawNextFrame:1.0f/60.0f]; // draw in the current opengl context

Whoah, that is so complicated. Is there an easier way?

Why yes, indeed there is! An example project has been included which implements a nice OpenGLES view to display a test .gif. So all you need to do once you make a GifVideo* is:

[playerView startAnimation:vid];

Why is there a modified version of lungif?

Normally lungif will keep around decoded versions of frames. Currently glgif does not use these frames - rather it decodes frames on the fly - so there is a hack which turns off the storage of these images via generateSavedImages.

If you want to use a normal version of lungif simply uncomment the following in GifVideo.m:

if (gifinfo)
    gifinfo->generateSavedImages = false;

Do any cool iPhone applications use this code?