GPUImageFramebufferCache类负责管理GPUImageFramebuffer对象，是一个GPUImageFramebuffer对象的缓存。

　　方法

　　- (GPUImageFramebuffer *)fetchFramebufferForSize:(CGSize)framebufferSize textureOptions:(GPUTextureOptions)textureOptions onlyTexture:(BOOL)onlyTexture

　　说明：从cache中获取一个GPUImageFramebuffer对象，如果获取失败，那么创建一个新的GPUImageFramebuffer对象。

　　参数：framebufferSize是对象的大小，textureOptions是纹理的配置信息，onlyTexture指示是否只为纹理，是否包含framebuffer对象。

　　返回：一个GPUImageFramebuffer对象

　　实现

 

- (GPUImageFramebuffer *)fetchFramebufferForSize:(CGSize)framebufferSize textureOptions:(GPUTextureOptions)textureOptions onlyTexture:(BOOL)onlyTexture;
{
    __block GPUImageFramebuffer *framebufferFromCache = nil;
//    dispatch_sync(framebufferCacheQueue, ^{
    runSynchronouslyOnVideoProcessingQueue(^{
        NSString *lookupHash = [self hashForSize:framebufferSize textureOptions:textureOptions onlyTexture:onlyTexture];
        NSNumber *numberOfMatchingTexturesInCache = [framebufferTypeCounts objectForKey:lookupHash];
        NSInteger numberOfMatchingTextures = [numberOfMatchingTexturesInCache integerValue];
        
        if ([numberOfMatchingTexturesInCache integerValue] < 1)
        {
            // Nothing in the cache, create a new framebuffer to use
            framebufferFromCache = [[GPUImageFramebuffer alloc] initWithSize:framebufferSize textureOptions:textureOptions onlyTexture:onlyTexture];
        }
        else
        {
            // Something found, pull the old framebuffer and decrement the count
            NSInteger currentTextureID = (numberOfMatchingTextures - 1);
            while ((framebufferFromCache == nil) && (currentTextureID >= 0))
            {
                NSString *textureHash = [NSString stringWithFormat:@"%@-%ld", lookupHash, (long)currentTextureID];
                framebufferFromCache = [framebufferCache objectForKey:textureHash];
                // Test the values in the cache first, to see if they got invalidated behind our back
                if (framebufferFromCache != nil)
                {
                    // Withdraw this from the cache while it's in use
                    [framebufferCache removeObjectForKey:textureHash];
                }
                currentTextureID--;
            }
            
            currentTextureID++;
            
            [framebufferTypeCounts setObject:[NSNumber numberWithInteger:currentTextureID] forKey:lookupHash];
            
            if (framebufferFromCache == nil)
            {
                framebufferFromCache = [[GPUImageFramebuffer alloc] initWithSize:framebufferSize textureOptions:textureOptions onlyTexture:onlyTexture];
            }
        }
    });

    [framebufferFromCache lock];
    return framebufferFromCache;
}

 

 

 

　　- (GPUImageFramebuffer *)fetchFramebufferForSize:(CGSize)framebufferSize onlyTexture:(BOOL)onlyTexture

　　说明：同上

　　实现

 

- (GPUImageFramebuffer *)fetchFramebufferForSize:(CGSize)framebufferSize onlyTexture:(BOOL)onlyTexture;
{
    GPUTextureOptions defaultTextureOptions;
    defaultTextureOptions.minFilter = GL_LINEAR;
    defaultTextureOptions.magFilter = GL_LINEAR;
    defaultTextureOptions.wrapS = GL_CLAMP_TO_EDGE;
    defaultTextureOptions.wrapT = GL_CLAMP_TO_EDGE;
    defaultTextureOptions.internalFormat = GL_RGBA;
    defaultTextureOptions.format = GL_BGRA;
    defaultTextureOptions.type = GL_UNSIGNED_BYTE;
    
    return [self fetchFramebufferForSize:framebufferSize textureOptions:defaultTextureOptions onlyTexture:onlyTexture];
}

 

　　- (void)returnFramebufferToCache:(GPUImageFramebuffer *)framebuffer

　　说明：向GP