image compression by 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);

    }