image compression by size - iPhone SDK

Here, JPEGRepresentation is quite memory consuming and if we use in Loop so it is extremely high memory consuming. So use below code & ImageSize won't be more then 200KB.

UIImage* newImage = [self captureView:yourUIView];


- (UIImage*)captureView:(UIView *)view {  
CGRect rect = view.bounds;
UIGraphicsBeginImageContext(rect.size);  
CGContextRef context = UIGraphicsGetCurrentContext();  

[view.layer renderInContext:context];  
UIImage* img = [UIImage alloc]init];
img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();  
NSLog(@"img=%@",img);
return img;
}

One way to do it, is to re-compress the file in a loop, until you find the desired size. You could first find height and width, and guess the compression factor (larger image more compression) then after you compress it, check the size, and split the difference again.

I know this is not super efficient, but I do not believe there is a single call to achieve a image of a specific size.

I took the answer of @kgutteridge and made a similar solution for Swift 3.0 using recursive:

extension UIImage {
    static func compress(image: UIImage, maxFileSize: Int, compression: CGFloat = 1.0, maxCompression: CGFloat = 0.4) -> Data? {

        if let data = UIImageJPEGRepresentation(image, compression) {

            let bcf = ByteCountFormatter()
            bcf.allowedUnits = [.useMB] // optional: restricts the units to MB only
            bcf.countStyle = .file
            let string = bcf.string(fromByteCount: Int64(data.count))
            print("Data size is: \(string)")

            if data.count > (maxFileSize * 1024 * 1024) && (compression > maxCompression) {
                let newCompression = compression - 0.1
                let compressedData = self.compress(image: image, maxFileSize: maxFileSize, compression: newCompression, maxCompression: maxCompression)
                return compressedData
            }

            return data
        }

        return nil
    }
}

Heres some example code that will attempt to compress an image for you so that it doesn't exceed either a max compression or maximum file size

CGFloat compression = 0.9f;
CGFloat maxCompression = 0.1f;
int maxFileSize = 250*1024;

NSData *imageData = UIImageJPEGRepresentation(yourImage, compression);

while ([imageData length] > maxFileSize && compression > maxCompression)
{
    compression -= 0.1;
    imageData = UIImageJPEGRepresentation(yourImage, compression);
}