iphone - 裁剪图像中的问题

Question

下面是我的代码，我在裁剪图像时遇到问题，谁能解决这个问题。

UIGraphicsBeginImageContext(self.view.bounds.size);

        CGContextRef context = UIGraphicsGetCurrentContext();

        CGContextMoveToPoint(context, newPoint1.x, newPoint1.y);
        CGContextAddLineToPoint(context, newPoint1.x, newPoint2.y);
        CGContextAddLineToPoint(context, newPoint2.x, newPoint2.y);
        CGContextAddLineToPoint(context, newPoint2.x, newPoint1.y);
        CGContextAddLineToPoint(context, newPoint1.x, newPoint1.y);
        CGContextClosePath(context);

        UIColor *blue = [UIColor colorWithRed: (0.0/255.0 ) green: (0.0/255.0) blue: (255.0/255.0) alpha:0.4];
        CGContextSetFillColorWithColor(context, blue.CGColor);

        CGContextDrawPath(context, kCGPathFillStroke);

Answer 1

留下这一切只需使用以下方法裁剪图像

- (UIImage *)captureScreenInRect:(CGRect)captureFrame
{

    CALayer *layer;
    layer = self.view.layer;
    UIGraphicsBeginImageContext(self.view.frame.size); 
    CGContextClipToRect (UIGraphicsGetCurrentContext(),captureFrame);
    [layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *screenImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return screenImage;
}

Answer 2

尝试这个。

- (UIImage*)imageByCropping:(UIImage *)imageToCrop toRect:(CGRect)rect
    {
       //create a context to do our clipping in
       UIGraphicsBeginImageContext(rect.size);
       CGContextRef currentContext = UIGraphicsGetCurrentContext();

       //create a rect with the size we want to crop the image to
       //the X and Y here are zero so we start at the beginning of our
       //newly created context
       CGRect clippedRect = CGRectMake(0, 0, rect.size.width, rect.size.height);
       CGContextClipToRect( currentContext, clippedRect);

       //create a rect equivalent to the full size of the image
       //offset the rect by the X and Y we want to start the crop
       //from in order to cut off anything before them
       CGRect drawRect = CGRectMake(rect.origin.x * -1,
                                    rect.origin.y * -1,
                                    imageToCrop.size.width,
                                    imageToCrop.size.height);

       //draw the image to our clipped context using our offset rect
       CGContextDrawImage(currentContext, drawRect, imageToCrop.CGImage);

       //pull the image from our cropped context
       UIImage *cropped = UIGraphicsGetImageFromCurrentImageContext();

       //pop the context to get back to the default
       UIGraphicsEndImageContext();

       //Note: this is autoreleased
       return cropped;
    }