Whatsapp like image compression

whatsapp-image-compression

- (UIImage *)compressImage:(UIImage *)image{
    float actualHeight = image.size.height;
    float actualWidth = image.size.width;
    float maxHeight = 600.0;
    float maxWidth = 800.0;
    float imgRatio = actualWidth/actualHeight;
    float maxRatio = maxWidth/maxHeight;
    float compressionQuality = 0.5;//50 percent compression
    
    if (actualHeight > maxHeight || actualWidth > maxWidth) {
        if(imgRatio < maxRatio){
            //adjust width according to maxHeight
            imgRatio = maxHeight / actualHeight;
            actualWidth = imgRatio * actualWidth;
            actualHeight = maxHeight;
        }
        else if(imgRatio > maxRatio){
            //adjust height according to maxWidth
            imgRatio = maxWidth / actualWidth;
            actualHeight = imgRatio * actualHeight;
            actualWidth = maxWidth;
        }else{
            actualHeight = maxHeight;
            actualWidth = maxWidth;
        }
    }
    
    CGRect rect = CGRectMake(0.0, 0.0, actualWidth, actualHeight);
    UIGraphicsBeginImageContext(rect.size);
    [image drawInRect:rect];
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    NSData *imageData = UIImageJPEGRepresentation(img, compressionQuality);
    UIGraphicsEndImageContext();

    return [UIImage imageWithData:imageData];
}

swift 5

    func resize() -> Data? {
        
        let maxHeight: CGFloat = 1136
        let maxWidth: CGFloat = 640
        
        var actualHeight = self.size.height
        var actualWidth = self.size.width

        var imgRatio = actualWidth / actualHeight
        let maxRatio = maxWidth / maxHeight
        var compressionQuality : CGFloat = 0.6
        
        if actualHeight > maxHeight || actualWidth > maxWidth {
            if imgRatio < maxRatio {
                //adjust width according to maxHeight
                imgRatio = maxHeight / actualHeight
                actualWidth = imgRatio * actualWidth
                actualHeight = maxHeight
            }
            else if imgRatio > maxRatio {
                //adjust height according to maxWidth
                imgRatio = maxWidth / actualWidth
                actualHeight = imgRatio * actualHeight
                actualWidth = maxWidth
            }
            else {
                actualHeight = maxHeight
                actualWidth = maxWidth
                compressionQuality = 1
            }
        }
        
        let canvas = CGSize(width: actualWidth, height: actualHeight)
        let format = imageRendererFormat
        format.opaque = true
        let result = UIGraphicsImageRenderer(size: canvas, format: format).image {
            _ in draw(in: CGRect(origin: .zero, size: canvas))
        }
        return result.jpegData(compressionQuality: compressionQuality)
    }

Hello,
One question, from where does maxHeight and maxWidth come from? was it also taken from WhatsApp?

Hi Diego,

maybe, a bit difficult to check (the initial version has been created 5 years ago).. in the current WhatsApp version I see 768*1024. here how you can see maxHeight and maxWidth

• open WhatsApp on a computer
• download an image
• check dimensions

Thanks, so I did that and it currently is 1280x960. But I disagree with compressionQuality = 1 in the else statement as that's the scenario where the ratios are the same, but the original image is obviously bigger, not smaller, so I do want it compressed.

Resizing with UIGraphicsImageRenderer is dead simple but consumes a lot of memory. So i suggest to use CGContext instead:

extension UIImage {
    func compressedData() -> Data? {
        let maxHeight: CGFloat = 1136
        let maxWidth: CGFloat = 640

        var actualHeight = size.height
        var actualWidth = size.width

        var imgRatio = actualWidth / actualHeight
        let maxRatio = maxWidth / maxHeight
        var compressionQuality : CGFloat = 0.6

        if actualHeight > maxHeight || actualWidth > maxWidth {
            if imgRatio < maxRatio {
                //adjust width according to maxHeight
                imgRatio = maxHeight / actualHeight
                actualWidth = imgRatio * actualWidth
                actualHeight = maxHeight
            }
            else if imgRatio > maxRatio {
                //adjust height according to maxWidth
                imgRatio = maxWidth / actualWidth
                actualHeight = imgRatio * actualHeight
                actualWidth = maxWidth
            }
            else {
                actualHeight = maxHeight
                actualWidth = maxWidth
                compressionQuality = 1
            }
        }

        guard let cgImage = cgImage else { return nil }

        let mutableData = NSMutableData()
        guard let imageDestinationRef = CGImageDestinationCreateWithData(mutableData as CFMutableData, kUTTypeJPEG, 1, nil) else { return nil }
        let options: NSDictionary = [
            kCGImageDestinationLossyCompressionQuality: compressionQuality
        ]
        CGImageDestinationAddImage(imageDestinationRef, cgImage, options)
        guard CGImageDestinationFinalize(imageDestinationRef) else { return nil }

        return mutableData as Data
    }
}

@knox kUTTypeJPEG deprecated

@YogeshPateliOS We can use UTType. jpeg.identifier