ios – 将CIImage转换为CGImage太慢了

Although a CIImage object has image data associated with it,it is not
an image. You can think of a CIImage object as an image “recipe.” A
CIImage object has all the information necessary to produce an image,
but Core Image doesn’t actually render an image until it is told to do
so. This “lazy evaluation” method allows Core Image to operate as
efficiently as possible.

这意味着,在渲染图像之前,您可能已经应用(或者更好地请求应用)到CIImage的任何过滤都不会实际发生,在您创建CGImageRef时会发生这种情况.这可能是你遇到减速的原因.

也就是说,过滤CIImage通常是一个非常快速的过程,所以根据你的图像大小,你应该给我们你的慢速定义.

最后要确保瓶颈确实在你认为的地方,你应该使用仪器profile your application.

编辑

我刚刚尝试构建一个示例项目,通过应用CIColorMap彩色滤镜在iPad3上过滤来自设备相机(960×540)的图像流,我的速度超过60fps(~16ms).

根据您的应用程序,您可以通过重用CIContext,ColorMapFilter,inputGradientImage(如果它不随时间变化)并在每次迭代时仅更新inputImage来获得更好的性能.

例如,您可以调用prepareFrameFiltering一次,然后在您要处理的每个帧上重复调用applyFilterToFrame :.

@property (nonatomic,strong) CIContext *context;
@property (nonatomic,strong) CIFilter *colorMapFilter;

- (void)prepareFrameFiltering {
    self.context = [CIContext contextWithOptions:nil];
    CIImage *colorMap = [CIImage imageWithCGImage:[UIImage imageNamed:@"gradient.jpg"].CGImage];
    self.colorMapFilter = [CIFilter filterWithName:@"CIColorMap"];
    [self.colorMapFilter setValue:colorMap forKey:@"inputGradientImage"];
}

- (void)applyFilterToFrame:(CIImage *)ciFrame {    
    // filter
    [self.colorMapFilter setValue:ciFrame forKey:@"inputImage"];
    CIImage *ciImageResult = [self.colorMapFilter valueForKey: @"outputImage"];

    CGImageRef ref = [self.context createCGImage:ciImageResult fromRect:ciFrame.extent];

    // do whatever you need

    CGImageRelease(ref);
}