iOS如何将图像的一部分绘制到特定的矩形？

Question

我想裁剪一张200*200的图片，裁剪的部分是(x=10,y=10,w=50,h=50)。并将这部分绘制到新的 500*500 图像上，新的矩形是 (x=30,y=30,w=50, h=50)，怎么做？

我可以用下面的方法获取图片的一部分

- (UIImage*) getSubImageWithRect: (CGRect) rect {

    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();

    // translated rectangle for drawing sub image
    CGRect drawRect = CGRectMake(-rect.origin.x, -rect.origin.y, self.size.width, self.size.height);

    // clip to the bounds of the image context
    // not strictly necessary as it will get clipped anyway?
    CGContextClipToRect(context, CGRectMake(0, 0, rect.size.width, rect.size.height));

    // draw image
    [self drawInRect:drawRect];
    // grab image
    UIImage* subImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return subImage;
}

Answer 1

让我们尝试使用以下代码块

- (UIImage*) getSubImageFromImage:(UIImage *)image
{
      // translated rectangle for drawing sub image
      CGRect drawRect = CGRectMake(10, 10, 50, 50);
      // Create Image Ref on Image
      CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], rect);
      // Get Cropped Image
      UIImage *img = [UIImage imageWithCGImage:imageRef];
      CGImageRelease(imageRef);
      return img;
}