Question

In iOS to save an UIImage as JPEG, I use UIImageJPEGRepresentation, however it doesn’t take options other than compression ratio. I wish to save the UIImage into progressive JPEG format, is there a easy way to do so?

Looks like in OS X there is an NSImageProgressive option to save NSImage to progressive format.

Answer 1

I think you can do it using the ImageIO framework, like this:

#import <UIKit/UIKit.h>
#import <ImageIO/ImageIO.h>
#import <MobileCoreServices/MobileCoreServices.h>
#import "AppDelegate.h"

int main(int argc, char *argv[])
{
    @autoreleasepool {
        UIImage *sourceImage = [UIImage imageNamed:@"test.jpg"];

        CFURLRef url = CFURLCreateWithString(NULL, CFSTR("file:///tmp/progressive.jpg"), NULL);
        CGImageDestinationRef destination = CGImageDestinationCreateWithURL(url, kUTTypeJPEG, 1, NULL);
        CFRelease(url);

        NSDictionary *jfifProperties = [NSDictionary dictionaryWithObjectsAndKeys:
            (__bridge id)kCFBooleanTrue, kCGImagePropertyJFIFIsProgressive,
            nil];

        NSDictionary *properties = [NSDictionary dictionaryWithObjectsAndKeys:
            [NSNumber numberWithFloat:.6], kCGImageDestinationLossyCompressionQuality,
            jfifProperties, kCGImagePropertyJFIFDictionary,
            nil];

        CGImageDestinationAddImage(destination, sourceImage.CGImage, (__bridge CFDictionaryRef)properties);
        CGImageDestinationFinalize(destination);
        CFRelease(destination);

        return 0;
    }
}

Preview.app says the output file is progressive, and ImageMagick’s identify command says it has “Interlace: JPEG”.