缩放和裁剪图像 ios答案

【问题标题】：scale and crop image ios缩放和裁剪图像 ios
【发布时间】：2012-07-21 23:49:15
【问题描述】：

我正在为 iOS 开发一个缩放和裁剪图像的功能（类似于 camara 应用程序），下面的代码可以正常工作，只是生成的图像是上下颠倒的，我想了解原因。

谢谢

- (UIImage*)imageByCropping:(UIImageView *)imageViewToCrop toRect:(CGRect)rect
{
    //create a context to do our clipping in
    CGRect newRect = CGRectApplyAffineTransform(rect, imageViewToCrop.transform);
    UIImage *imageToCrop = imageViewToCrop.image;
    UIGraphicsBeginImageContext(newRect.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);


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

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

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

    return cropped;

}

【问题讨论】：

标签： ios objective-c uiimage scale crop

【解决方案1】：

我也遇到过这个问题，没有解释。但是找到了解决该问题的解决方法。只需将以下两行放入您的代码中，然后再试一次。它对我有用。

CGContextTranslateCTM(context, 0.0, newRect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);//flip context

【讨论】：