GPUImageFilterGroup is returning black image

Question

I have been working on this all day and am unable to find where my error is. This is my first experience using GPUImage. I am following the comments on the issues in GitHub as well as questions I have found here with no luck.

My GPUImageFilterGroup is returning a black image, but the filters in the group that I am using individually work on their own. I am simply trying to edit saturation and levels on a still image.

GPUImageFilterGroup* blackAndWhiteGroup = [[GPUImageFilterGroup alloc] init];

GPUImageSaturationFilter *satuaration = [[GPUImageSaturationFilter alloc] init];
[satuaration setSaturation:0.0];

GPUImageLevelsFilter *levels = [[GPUImageLevelsFilter alloc] init];
[levels setMin:56.0/255.0 gamma:1.15 max:255.0/255.0];

[blackAndWhiteGroup addFilter:satuaration];
[blackAndWhiteGroup addFilter:levels];

[satuaration addTarget:levels];

[blackAndWhiteGroup setInitialFilters:[NSArray arrayWithObject:satuaration]];
[blackAndWhiteGroup setTerminalFilter:levels];

I have tried two different ways for applying the filter to the image, neither are working for me but I think this is where my problem lies.

First attempt:

GPUImagePicture *stillImage= [[GPUImagePicture alloc] initWithImage:takenPhoto];
[stillImage addTarget:blackAndWhiteGroup];
[stillImage processImage];

UIImage *blackAndWhiteFilteredImage = [blackAndWhiteGroup imageFromCurrentFramebuffer];
self.imageView.image = blackAndWhiteFilteredImage;

Second attempt:

UIImage *blackAndWhiteFilteredImage = [blackAndWhiteGroup imageByFilteringImage:takenPhoto];
self.imageView.image = blackAndWhiteFilteredImage;

Thanks in advance.

Answer 1

As I stated in the comment, you need to call:

[blackAndWhiteGroup useNextFrameForImageCapture];

before calling:

[stillImage processImage];

This is for the updated version of the GPUImage library. Hope this helps out future questions!