Add UIImage Element using GPUImage Framework - ios

Question

I am using Brad Larson's GPUImage Framework to add a UIImage element,i have successfully added the image but the main issue is that the image is getting stretched to the video's aspect ratio.
Here is my code:
GPUImageView *filterView = (GPUImageView *)self.view;
videoCamera = [[GPUImageVideoCamera alloc] initWithSessionPreset:AVCaptureSessionPreset640x480 cameraPosition:AVCaptureDevicePositionBack];
videoCamera.outputImageOrientation = UIInterfaceOrientationPortrait;
transformFilter=[[GPUImageTransformFilter alloc]init];
CGAffineTransform t=CGAffineTransformMakeScale(0.5, 0.5);
[(GPUImageTransformFilter *)filter setAffineTransform:t];
[videoCamera addTarget:transformFilter];
filter = [[GPUImageOverlayBlendFilter alloc] init];
[videoCamera addTarget:filter];
inputImage = [UIImage imageNamed:#"eye.png"];
sourcePicture = [[GPUImagePicture alloc] initWithImage:inputImage smoothlyScaleOutput:YES];
[sourcePicture forceProcessingAtSize:CGSizeMake(50, 50)];
[sourcePicture processImage];
[sourcePicture addTarget:filter];
[sourcePicture addTarget:transformFilter];
[filter addTarget:filterView];
[videoCamera startCameraCapture];
I have tried to use transform filter before blending the image,but it isn't getting scaled.
I want the image to appear at the center.How do i do it?
Thanks

Answer 1

You are on the right track, just have a few things out of place.
The following code will load an overlay image and apply a transformation to keep it at actual size. By default is will be centered over the video.
GPUImageView *filterView = (GPUImageView *)self.view;
videoCamera = [[GPUImageVideoCamera alloc] initWithSessionPreset:AVCaptureSessionPreset640x480 cameraPosition:AVCaptureDevicePositionBack];
videoCamera.outputImageOrientation = UIInterfaceOrientationPortrait;
filter = [[GPUImageOverlayBlendFilter alloc] init];
transformFilter = [[GPUImageTransformFilter alloc]init];
[videoCamera addTarget:filter];
[transformFilter addTarget:filter];
// setup overlay image
inputImage = [UIImage imageNamed:#"eye.png"];
sourcePicture = [[GPUImagePicture alloc] initWithImage:inputImage smoothlyScaleOutput:YES];
// determine the necessary scaling to keep image at actual size
CGFloat tx = inputImage.size.width / 480.0; // 480/640: based on video camera preset
CGFloat ty = inputImage.size.height / 640.0;
// apply transform to filter
CGAffineTransform t = CGAffineTransformMakeScale(tx, ty);
[(GPUImageTransformFilter *)transformFilter setAffineTransform:t];
//
[sourcePicture addTarget:filter];
[sourcePicture addTarget:transformFilter];
[sourcePicture processImage];
[filter addTarget:filterView];
[videoCamera startCameraCapture];