Swiftgram/submodules/FastBlur/Sources/ApplyScreenshotEffect.m

#import <FastBlur/ApplyScreenshotEffect.h>

#import <Accelerate/Accelerate.h>
#import <float.h>

UIImage * _Nullable applyBlurWithRadius(UIImage *image, CGFloat blurRadius, UIColor * tintColor, CGFloat saturationDeltaFactor, UIImage * _Nullable maskImage) {
    // Check pre-conditions.
    if (image.size.width < 1 || image.size.height < 1) {
        NSLog (@"*** error: invalid size: (%.2f x %.2f). Both dimensions must be >= 1: %@", image.size.width, image.size.height, image);
        return nil;
    }
    if (!image.CGImage) {
        NSLog (@"*** error: image must be backed by a CGImage: %@", image);
        return nil;
    }
    if (maskImage && !maskImage.CGImage) {
        NSLog (@"*** error: maskImage must be backed by a CGImage: %@", maskImage);
        return nil;
    }
    
    CGRect imageRect = { CGPointZero, image.size };
    UIImage *effectImage = image;
    
    BOOL hasBlur = blurRadius > __FLT_EPSILON__;
    BOOL hasSaturationChange = fabs(saturationDeltaFactor - 1.) > __FLT_EPSILON__;
    if (hasBlur || hasSaturationChange) {
        UIGraphicsBeginImageContextWithOptions(image.size, NO, [[UIScreen mainScreen] scale]);
        CGContextRef effectInContext = UIGraphicsGetCurrentContext();
        CGContextScaleCTM(effectInContext, 1.0, -1.0);
        CGContextTranslateCTM(effectInContext, 0, -image.size.height);
        CGContextDrawImage(effectInContext, imageRect, image.CGImage);
        
        vImage_Buffer effectInBuffer;
        effectInBuffer.data     = CGBitmapContextGetData(effectInContext);
        effectInBuffer.width    = CGBitmapContextGetWidth(effectInContext);
        effectInBuffer.height   = CGBitmapContextGetHeight(effectInContext);
        effectInBuffer.rowBytes = CGBitmapContextGetBytesPerRow(effectInContext);
        
        UIGraphicsBeginImageContextWithOptions(image.size, NO, [[UIScreen mainScreen] scale]);
        CGContextRef effectOutContext = UIGraphicsGetCurrentContext();
        vImage_Buffer effectOutBuffer;
        effectOutBuffer.data     = CGBitmapContextGetData(effectOutContext);
        effectOutBuffer.width    = CGBitmapContextGetWidth(effectOutContext);
        effectOutBuffer.height   = CGBitmapContextGetHeight(effectOutContext);
        effectOutBuffer.rowBytes = CGBitmapContextGetBytesPerRow(effectOutContext);
        
        if (hasBlur) {
            // A description of how to compute the box kernel width from the Gaussian
            // radius (aka standard deviation) appears in the SVG spec:
            // http://www.w3.org/TR/SVG/filters.html#feGaussianBlurElement
            //
            // For larger values of 's' (s >= 2.0), an approximation can be used: Three
            // successive box-blurs build a piece-wise quadratic convolution kernel, which
            // approximates the Gaussian kernel to within roughly 3%.
            //
            // let d = floor(s * 3*sqrt(2*pi)/4 + 0.5)
            //
            // ... if d is odd, use three box-blurs of size 'd', centered on the output pixel.
            //
            CGFloat inputRadius = blurRadius * [[UIScreen mainScreen] scale];
            NSUInteger radius = (NSUInteger)(floor(inputRadius * 3.0f * ((CGFloat)sqrt(2 * M_PI)) / 4 + 0.5f));
            if (radius % 2 != 1) {
                radius += 1; // force radius to be odd so that the three box-blur methodology works.
            }
            vImageBoxConvolve_ARGB8888(&effectInBuffer, &effectOutBuffer, NULL, 0, 0, (uint32_t)radius, (uint32_t)radius, 0, kvImageEdgeExtend);
            vImageBoxConvolve_ARGB8888(&effectOutBuffer, &effectInBuffer, NULL, 0, 0, (uint32_t)radius, (uint32_t)radius, 0, kvImageEdgeExtend);
            vImageBoxConvolve_ARGB8888(&effectInBuffer, &effectOutBuffer, NULL, 0, 0, (uint32_t)radius, (uint32_t)radius, 0, kvImageEdgeExtend);
        }
        BOOL effectImageBuffersAreSwapped = NO;
        if (hasSaturationChange) {
            CGFloat s = saturationDeltaFactor;
            CGFloat floatingPointSaturationMatrix[] = {
                0.0722f + 0.9278f * s,  0.0722f - 0.0722f * s,  0.0722f - 0.0722f * s,  0,
                0.7152f - 0.7152f * s,  0.7152f + 0.2848f * s,  0.7152f - 0.7152f * s,  0,
                0.2126f - 0.2126f * s,  0.2126f - 0.2126f * s,  0.2126f + 0.7873f * s,  0,
                0,                    0,                    0,  1,
            };
            const int32_t divisor = 256;
            NSUInteger matrixSize = sizeof(floatingPointSaturationMatrix)/sizeof(floatingPointSaturationMatrix[0]);
            int16_t saturationMatrix[matrixSize];
            for (NSUInteger i = 0; i < matrixSize; ++i) {
                saturationMatrix[i] = (int16_t)floor(floatingPointSaturationMatrix[i] * divisor);
            }
            if (hasBlur) {
                vImageMatrixMultiply_ARGB8888(&effectOutBuffer, &effectInBuffer, saturationMatrix, divisor, NULL, NULL, kvImageNoFlags);
                effectImageBuffersAreSwapped = YES;
            }
            else {
                vImageMatrixMultiply_ARGB8888(&effectInBuffer, &effectOutBuffer, saturationMatrix, divisor, NULL, NULL, kvImageNoFlags);
            }
        }
        if (!effectImageBuffersAreSwapped)
            effectImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        
        if (effectImageBuffersAreSwapped)
            effectImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }
    
    // Set up output context.
    UIGraphicsBeginImageContextWithOptions(image.size, NO, [[UIScreen mainScreen] scale]);
    CGContextRef outputContext = UIGraphicsGetCurrentContext();
    CGContextScaleCTM(outputContext, 1.0, -1.0);
    CGContextTranslateCTM(outputContext, 0, -image.size.height);
    
    // Draw base image.
    CGContextDrawImage(outputContext, imageRect, image.CGImage);
    
    // Draw effect image.
    if (hasBlur) {
        CGContextSaveGState(outputContext);
        if (maskImage) {
            CGContextClipToMask(outputContext, imageRect, maskImage.CGImage);
        }
        CGContextDrawImage(outputContext, imageRect, effectImage.CGImage);
        CGContextRestoreGState(outputContext);
    }
    
    // Add in color tint.
    if (tintColor) {
        CGContextSaveGState(outputContext);
        CGContextSetFillColorWithColor(outputContext, tintColor.CGColor);
        CGContextFillRect(outputContext, imageRect);
        CGContextRestoreGState(outputContext);
    }
    
    // Output image is ready.
    UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return outputImage;
}

UIImage * _Nullable applyScreenshotEffectToImage(UIImage * _Nonnull image) {
    return applyBlurWithRadius(image, 10.0f, nil, 1.8f, nil);
}