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; 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:
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?
The only app at the moment is anim8gif.