从UITextView或UILabel中提取UIImage会产生白色图像 [英] pulling an UIImage from a UITextView or UILabel gives white image

问题描述

我需要从UITextView或UILabel中获取UIImage。我有一个方法可以从其他类型的视图（[UIViewController视图]，MKMapView，UIButtons）成功提取图像，但我只是为我的UITextView获取白色矩形。

I need to grab an UIImage from a UITextView or UILabel. I've got a method that will pull an image successfully from other types of views ( [UIViewController view], MKMapView, UIButtons) but I am just getting a white rect for my UITextView.

我一直把头靠在墙上一段时间，并怀疑一些非常非常基本的东西。

I've been banging my head against the wall for a while and suspect something really, really basic.

非常感谢！

@interface TaskAccomplishmentViewController : UIViewController {

    MKMapView *mapView;
    UILabel *timeLeftText;
    UITextView *challengeText;

    UIButton *successButton;

<snip>

- (void) setChallangeImageToImageFromChallenge {

    // works
    // [currChallenge setChallengeImage:[UIImageUtils grabImageFromView:mapView]];
    // [currChallenge setChallengeImage:[UIImageUtils grabImageFromView:[self view]]];
    // [currChallenge setChallengeImage:[UIImageUtils grabImageFromView:successButton]];

    // doesn't work
    // [currChallenge setChallengeImage:[UIImageUtils grabImageFromView:timeLeftText]];
    [currChallenge setChallengeImage:[UIImageUtils grabImageFromView:challengeText]];

}

和UIView代码中的grabImage

and the grabImage from a UIView code

+(UIImage *)grabImageFromView: (UIView *) viewToGrab {

    UIGraphicsBeginImageContext(viewToGrab.bounds.size);

    [[viewToGrab layer] renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return viewImage;
}

推荐答案

技术是正确的。也许是因为文字被翻转了。您可以尝试为坐标系和原点设置变换。就像你在绘制文字时通常所做的那样。

The technique is correct. Maybe it is because text is flipped. You could try to set a transform for the coordinate system and origin. Like you would normally do when drawing text.

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