Add borders to a video using GPUImage

Question

I'm trying to add borders of specified colors to a video to get something like this http://d.pr/i/1WXs

Here is what I'm doing

GPUImageNormalBlendFilter *blendFilter = [GPUImageNormalBlendFilter new];

_movie = [[GPUImageMovie alloc] initWithURL:_movieUrl];

_sourcePicture = [[GPUImagePicture alloc] initWithImage:[self imageWithColor:RGBACOLOR(255, 0, 0, 0.5f)]];
[_sourcePicture processImage];

[_sourcePicture addTarget:blendFilter atTextureLocation:0];
[_movie addTarget:blendFilter atTextureLocation:1];

[blendFilter addTarget:_videoView];

[_movie startProcessing];

As I understand, transform filter can't resize video to add a whitespace? How can I achieve this?

Thanks.

Answer 1

Solved using chain of Transform & Crop filter.

[transformFilter setBackgroundColorRed:1 green:0 blue:0 alpha:0]; // For example

// Calculate scale for exact crop size
// For 16x9 scale = 16 * videoSize.height / (9 * videoSize.width);
CGFloat scale = [self scaleForCropSize:self.cropSize];
transformFilter.affineTransform = CGAffineTransformMakeScale(scale, scale);

CGSize videoSize = [self.paramsContainer.videoTrack naturalSize];
CGRect cropRegion;
if (videoSize.width > videoSize.height) {
    cropRegion = CGRectMake((1 - scale) / 2, 0, scale, 1);
} else {
    cropRegion = CGRectMake(0, (1 - scale) / 2, 1, scale);
}

cropFilter.cropRegion = cropRegion;