GPUImage output image is missing in screen capture - ios

Question

I am trying to capture screen portion to post image on social media.
I am using following code to capture screen.
- (UIImage *) imageWithView:(UIView *)view
{
UIGraphicsBeginImageContextWithOptions(view.bounds.size, NO, 0.0);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return img;
}
Above code is perfect for capturing screen.
Problem :
My UIView contains GPUImageView with the filtered image. When I tries to capture screen using above code, that particular portion of GPUImageView does not contains the filtered image.
I am using GPUImageSwirlFilter with the static image (no camera). I have also tried
UIImage *outImage = [swirlFilter imageFromCurrentFramebuffer]
but its not giving image.
Note : Following is working code, which gives perfect output of swirl effect, but I want same image in UIImage object.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
GPUImageSwirlFilter *swirlFilter = [GPUImageSwirlFilter alloc] init];
swirlLevel = 4;
[swirlFilter setAngle:(float)swirlLevel/10];
UIImage *inputImage = [UIImage imageNamed:gi.wordImage];
GPUImagePicture *swirlSourcePicture = [[GPUImagePicture alloc] initWithImage:inputImage];
inputImage = nil;
[swirlSourcePicture addTarget:swirlFilter];
dispatch_async(dispatch_get_main_queue(), ^{
[swirlFilter addTarget:imgSwirl];
[swirlSourcePicture processImage];
// This works perfect and I have filtered image in my imgSwirl. But I want
// filtered image in UIImage to use at different place like posting
// on social media
sharingImage = [swirlFilter imageFromCurrentFramebuffer]; // This also
// returns nothing.
});
});
1) Am I doing something wrong with GPUImage's imageFromCurrentFramebuffer ?
2) And why does screen capture code is not including GPUImageView portion in output image ?
3) How do I get filtered image in UIImage ?

Answer 1

First, -renderInContext: won't work with a GPUImageView, because a GPUImageView renders using OpenGL ES. -renderinContext: does not capture from CAEAGLLayers, which are used to back views presenting OpenGL ES content.
Second, you're probably getting a nil image in the latter code because you've forgotten to set -useNextFrameForImageCapture on your filter before triggering -processImage. Without that, your filter won't hang on to its backing framebuffer long enough to capture an image from it. This is due to a recent change in the way that framebuffers are handled in memory (although this change did not seem to get communicated very well).