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我正在尝试绘制一些文本，它在非视网膜显示器上很好，但在视网膜显示器上它不是高分辨率的。

这是我的 iPad Air 的截图：

在此处输入图像描述

请参阅下面的代码，它实际上将文本绘制成半透明的，周围有一个几乎不透明的蒙版，因此您可以通过文本看到图像。

-(void) maskImage:(UIImageView *)imageView withText:(NSString *)text font:(UIFont *)font attributes:(NSDictionary *)attributes yOffset:(CGFloat)yOffset 
{ 
  NSStringDrawingContext *paraContext = [[NSStringDrawingContext alloc] init];
  NSStringDrawingOptions stringDrawingOptions = NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingTruncatesLastVisibleLine;

  // find out how much space we need for the text
  CGSize textSize = CGSizeIntegral([text boundingRectWithSize:CGSizeMake(kNowPlayingTrackDetailsMaxWidth, kNowPlayingTrackDetailsMaxHeight) options:stringDrawingOptions attributes:attributes context:paraContext].size);

  // set up the frame for drawing the text, including some padding

  CGSize drawingSize = {textSize.width + 80, textSize.height + 60};
  CGRect drawingFrame = { 0, 0, drawingSize.width, drawingSize.height};
  CGRect textFrame = { 40, 30, textSize.width, textSize.height };

  UIGraphicsBeginImageContextWithOptions(drawingSize, YES, 0);

  UIColor *bgColor = [UIColor colorWithWhite:1 alpha:.98];
  [bgColor setFill];
  [bgColor setStroke];

  UIBezierPath *path = [UIBezierPath bezierPathWithRect:drawingFrame];
  [path fill];

  // draw the text

  [text drawWithRect:textFrame options:stringDrawingOptions attributes:attributes context:paraContext];
  UIImage *textImage = UIGraphicsGetImageFromCurrentImageContext();

  UIGraphicsEndImageContext();

  // now create an image mask from the text image

  CIImage *inputImage = [CIImage imageWithCGImage:textImage.CGImage];
  CIFilter *filter = [CIFilter filterWithName:@"CIMaskToAlpha" keysAndValues:kCIInputImageKey, inputImage, nil];
  CIImage *outputImage = [filter outputImage];

  imageView.image = [UIImage imageWithCIImage:outputImage];

  // final set the UIImageView size to match the drawing size
  CGRect imageViewFrame = imageView.frame;
  imageViewFrame.size = drawingSize;
  imageView.frame = imageViewFrame;
}
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1 回答 1

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Oliver Jones 帮我解决了这个问题。谢谢@orj！

答案是创建 UIImage

    [UIImage imageWithCIImage:outputImage scale:textImage.scale orientation:UIImageOrientationUp];

代替

    imageView.image = [UIImage imageWithCIImage:outputImage];

这正确设置了输出图像的比例。

于 2014-07-18T05:28:56.933 回答