在ios中合并重叠图像

Question

我试图通过根据给定字符串选择随机图像来制作单个图像。为此，我正在编写以下代码，它完全正常：

int count=self.txtFld.text.length;
self.imgView3.image=nil;

UIButton *btn=(UIButton*)sender;
  if(btn.tag==1)
   {

    NSLog(@"Blackaddr Btn Clicked..");

    int i=0;
    while (i<count) {
        UIImage *img=self.imgView1.image;
        CGSize size = CGSizeMake(self.imgView3.image.size.width+img.size.width-10, img.size.height);
        UIGraphicsBeginImageContext(size);

        [self.imgView3.image drawInRect:CGRectMake(0, 0, self.imgView3.image.size.width, self.imgView3.image.size.height)];
        [img drawInRect:CGRectMake(self.imgView3.image.size.width-10,0,img.size.width, size.height)];
        UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext();

        UIGraphicsEndImageContext();
        self.imgView3.image = finalImage;
        [self.imgView3 setFrame:CGRectMake(self.imgView3.frame.origin.x, self.imgView3.frame.origin.y, finalImage.size.width, finalImage.size.height)];
        i++;
    }
}

现在我想重叠这些图像，即第二张图像应该在第一张图像后面，并将图像置于中心。