CGContext pdf页面方面适合 [英] CGContext pdf page aspect fit

问题描述

我在CGContext上使用代码显示pdf页面

I am displaying a pdf page on the CGContext using the code

- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)context
{
    CGContextSetRGBFillColor(ctx, 1.0, 1.0, 1.0, 1.0);
    CGContextFillRect(ctx, layer.bounds);
    CGContextTranslateCTM(ctx, 0.0, layer.bounds.size.height);
    CGContextScaleCTM(ctx, 1.0, -1.0);
    CGContextConcatCTM(ctx, CGPDFPageGetDrawingTransform(myPageRef, kCGPDFBleedBox, layer.bounds, 0, true));
    CGContextDrawPDFPage(ctx, myPageRef);
}

问题是pdf页面是在页面中心绘制的四面都有边界。有没有办法让页面适合屏幕。

The problem is that the pdf page is getting drawn on the center of the page leaving border on all four sides. Is there any way to make the page fit to screen.

推荐答案

扩展Tia的答案;内置方法CGPDFPageGetDrawingTransform将缩小但不会向上缩放。如果要扩展，则需要通过将CGPDFGetBoxRect的结果与内容区域进行比较来计算出自己的转换。即席打字：

To expand on Tia's answer; the built-in method CGPDFPageGetDrawingTransform will scale down but not up. If you want to scale up then you need to work out your own transform by comparing the results of CGPDFGetBoxRect to your content area. Typing extemporaneously:

- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)context
{
    CGContextSetRGBFillColor(ctx, 1.0, 1.0, 1.0, 1.0);
    CGContextFillRect(ctx, layer.bounds);
    CGContextTranslateCTM(ctx, 0.0, layer.bounds.size.height);
    CGContextScaleCTM(ctx, 1.0, -1.0);

    CGRect cropBox = CGPDFGetBoxRect(myPageRef, kCGPDFCropBox);
    CGRect targetRect = layer.bounds;
    CGFloat xScale = targetRect.size.width / cropBox.size.width;
    CGFloat yScale = targetRect.size.height / cropBox.size.height;
    CGFloat scaleToApply = xScale < yScale ? xScale : yScale;
    CGContextConcatCTM(ctx, CGAffineTransformMakeScale(scaleToApply, scaleToApply)); 

    CGContextDrawPDFPage(ctx, myPageRef);
}

所以：计算你需要多少钱来缩放文档它占据视图的整个宽度，占据整个高度多少，然后实际按这两个值的较小值进行缩放。

So: work out how much you'd have to scale the document by for it to occupy the entire width of the view, how much to occupy the entire height and then actually scale by the lesser of those two values.

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