ios中图片的绘画和截图

CGImageCreateWithImageInRect截图和UIGraphicsGetImageFromCurrentImageContext绘画图片

使用CGImageCreateWithImageInRect截图

    UIImage *img1 = [UIImage imageNamed:@"123"];

    //截取图片

        CGImageRef imgSmall = CGImageCreateWithImageInRect(img1.CGImage, CGRectMake(100, 100, 100, 100));

        UIImage *img2 = [UIImage imageWithCGImage:imgSmall];

        UIImageView *imgView = [[UIImageView alloc] initWithImage:img2];

        [imgView setFrame:CGRectMake(0, 100, 100, 100)];

        [self.view addSubview:imgView];

使用UIGraphicsGetImageFromCurrentImageContext绘画图片

UIImage *img1 = [UIImage imageNamed:@"123"];

UIImage *img2 = [UIImage imageNamed:@"123"];

    //开始绘画，设置画布的大小

UIGraphicsBeginImageContext(CGSizeMake(img1.size.width, img1.size.height * 2));

    //将图片画进去

[img1 drawInRect:CGRectMake(0, 0, img1.size.width, img1.size.height)];

[img2 drawInRect:CGRectMake(0,img1.size.height,  img1.size.width,  img1.size.height)];

    //就画布中的内容，放置到图片中

UIImage *img3 = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

    //在视图中显示

UIImageView *imgView = [[UIImageView alloc] initWithImage:img3];

[imgView setFrame:CGRectMake(0, 100, 100, 100)];

[self.view addSubview:imgView];