Resampling Image with GUIImage

resample_image.m

+ (UIImage *)compressForUpload:(UIImage *)original
{
    // Calculate new size given scale factor.
    CGSize originalSize = original.size;
    CGFloat longerBorder = MAX(originalSize.width, originalSize.height);
    CGFloat scale = longerBorder > MAX_DISTANCE_OF_LONGER_EDGE ? longerBorder / MAX_DISTANCE_OF_LONGER_EDGE : 1;
    CGSize newSize = CGSizeMake(originalSize.width / scale, originalSize.height / scale);

    GPUImageLanczosResamplingFilter *resampleFilter = [[GPUImageLanczosResamplingFilter alloc] init];
    [resampleFilter forceProcessingAtSize:newSize];
    return [resampleFilter imageByFilteringImage:original];
}