两张图片合成

是在一个图片上加了两外一张图片合成为一张

UIImage *image =  [UIImage imageNamed:@"big"];

    UIImage *waterMark ＝ [UIImage imageNamed:@"small"];;

    UIGraphicsBeginImageContext(image.size);

    // Draw image2

    [image drawInRect:CGRectMake(0, 0, image.size.width, image.size.height)];

    // Draw image1

    if (image.size.width>image.size.height) {

        [waterMark drawInRect:CGRectMake(0, 0, image.size.height/2, image.size.height/2)];

    }

    else{

         [waterMark drawInRect:CGRectMake(0, 0, image.size.width/2, image.size.width/2)];

    }

    UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();