imageFromCurrentFramebufferWithOrientation返回nil GPUImagePicture？

Question

我想将图片转换为黑白。我尝试了以下代码，但imageFromCurrentFramebufferWithOrientation总是返回nil。

-(UIImage *)convertImageToBlackAndWhite:(UIImage *)image{
GPUImagePicture *gpuImage = [[GPUImagePicture alloc] initWithImage:image];
GPUImageSobelEdgeDetectionFilter *edgeFilter = [[GPUImageSobelEdgeDetectionFilter alloc] init];

GPUImageColorMatrixFilter *conversionFilter = [[GPUImageColorMatrixFilter alloc] init];
conversionFilter.colorMatrix = (GPUMatrix4x4){
    {0.0, 0.0, 0.0, 1.0},
    {0.0, 0.0, 0.0, 1.0},
    {0.0, 0.0, 0.0, 1.0},
    {1.0,0.0,0.0,0.0},
};

[gpuImage addTarget:edgeFilter];
[edgeFilter addTarget:conversionFilter];
[gpuImage processImage];
NSLog(@"%@",[conversionFilter imageFromCurrentFramebufferWithOrientation:0]);
return [conversionFilter imageFromCurrentFramebufferWithOrientation:0];

}

Answer 1

每the recent changes in the way that GPUImage handles framebuffers，您需要添加一行

[conversionFilter useNextFrameForImageCapture];

之前

[gpuImage processImage];

在上面的代码中。在处理完图像并从中捕获结果之前，您需要让框架知道不要为最后一个过滤器回收帧缓冲区。