Question

我正在使用代码

在CGContext上显示pdf页面

- (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页面被绘制在页面的中心，在所有四个边上留下边界。有没有办法让页面适合屏幕。

Answer 1

扩展Tia的答案;内置方法CGPDFPageGetDrawingTransform将缩小但不会向上缩放。如果你想扩展，那么你需要通过比较CGPDFGetBoxRect与你的内容区域的结果来计算你自己的转换。即席打字：

- (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：弄清楚你需要多大程度地缩放文档，使其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。

Answer 2

如果PDF页面矩形小于CGPDFPageGetDrawingTransform参数，rect将不会返回向上扩展转换。

Answer 3

粗略阅读您的代码建议kCGPDFBleedBox的使用应替换为其他设置，可能是kCGPDFMediaBox。有关详细信息，请参阅here。

Answer 4

其他答案是正确的，CGPDFPageGetDrawingTransform不会向上扩展，但是您可以缩小矩形以仅捕获所选框。使用CGPDFPageGetBoxRect（）并按照Tommy在接受的答案中建议的比例计算比例，然后使用它来缩小传递给CGPDFPageGetDrawingTransform（）的捕获矩形。

- (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);

    CGRect box = CGPDFGetBoxRect(myPageRef, kCGPDFBleedBox);
    CGFloat xScale = layer.bounds.size.width / cropBox.size.width;
    CGFloat yScale = layer.bounds.size.height / cropBox.size.height;
    CGFloat scaleToApply = xScale < yScale ? xScale : yScale;

    CGRect captureRect = CGRectMake(0, 0,
                                    layer.bounds.size.width/scaleToApply,
                                    layer.bounds.size.height/scaleToApply);

    CGAffineTransform drawXfm = CGPDFPageGetDrawingTransform(myPageRef,
                                                             kCGPDFBleedBox,
                                                             captureRect,
                                                             0,
                                                             true);

    CGContextScaleCTM(ctx, scaleToApply, -scaleToApply);
    CGContextConcatCTM(ctx, drawXfm);
    CGContextDrawPDFPage(ctx, myPageRef);
}

然后它也很容易扩展到处理景观：

- (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);

    CGRect box = CGPDFGetBoxRect(myPageRef, kCGPDFBleedBox);
    int rotate;
    CGFloat xScale, yScale;
    if (box.size.width > box.size.height) {
        // landscape
        rotate = 270;
        xScale = layer.bounds.size.height / cropBox.size.width;
        yScale = layer.bounds.size.width / cropBox.size.height;
    } else {
        // portrait
        rotate = 0;
        xScale = layer.bounds.size.width / cropBox.size.width;
        yScale = layer.bounds.size.height / cropBox.size.height;
    }
    CGFloat scaleToApply = xScale < yScale ? xScale : yScale;

    CGRect captureRect = CGRectMake(0, 0,
                                    layer.bounds.size.width/scaleToApply,
                                    layer.bounds.size.height/scaleToApply);

    CGAffineTransform drawXfm = CGPDFPageGetDrawingTransform(myPageRef,
                                               kCGPDFBleedBox,
                                               captureRect,
                                               rotate,
                                               true);

    CGContextScaleCTM(ctx, scaleToApply, -scaleToApply);
    CGContextConcatCTM(ctx, drawXfm);
    CGContextDrawPDFPage(ctx, myPageRef);
}

Answer 5

这是我的解决方案，它也处理旋转。可能有用。

// Create transformation
int rotation = CGPDFPageGetRotationAngle(pdfPage);
CGRect rect = CGPDFPageGetBoxRect(pdfPage, kCGPDFCropBox);
CGRect rotatedRect = rect;
CGRectApplyAffineTransform(rotatedRect, CGAffineTransformMakeRotation(M_PI * rotation / 180.0));

CGFloat scale = MIN(self.bounds.size.width / rotatedRect.size.width, self.bounds.size.height / rotatedRect.size.height);
// Scale
CGContextConcatCTM(context, CGAffineTransformMakeScale(scale, scale));  
// Move left bottom cornet to 0, 0
CGContextConcatCTM(context, CGAffineTransformMakeTranslation(rotatedRect.size.width * 0.5, rotatedRect.size.height * 0.5));    
// Rotate
CGContextConcatCTM(context, CGAffineTransformMakeRotation(-M_PI * rotation / 180.0));    
// Move center into 0, 0
CGContextConcatCTM(context, CGAffineTransformMakeTranslation(-rect.origin.x - rect.size.width * 0.5, -rect.origin.y - rect.size.height * 0.5));

CGContextDrawPDFPage(context, pdfPage);

CGContext pdf页面方面适合

5 个答案: