编辑PDF并在UIWebView中显示图像时，缩放比例不合适 [英] Inappropriate scaling factor when editing PDF and displaying image in UIWebView

问题描述

我正在努力地进行PDF编辑，所以我从朴素的代码开始尝试实现以下目标:

I'm struggling with PDF editing so I'm starting with naive code trying to achieve the following :

• 显示与应用程序捆绑在一起的PDF
• 单击要添加图像的屏幕(例如签名)
• 使用编辑的PDF重新加载Web视图

这是我在github上的代码: https://github.com/HRiffiod/PDFSignature.git

Here is my code on github : https://github.com/HRiffiod/PDFSignature.git

问题是我的图像未显示在编辑的PDF中的正确位置.它不是随机的，但是我离(0,0)坐标越远，偏差越大，这就是为什么我押错了缩放比例的原因.

The problem is that my image does not display at the right position in the edited PDF. It is not random, but the farther I get from the (0,0) coordinates, the bigger the deviation, that's why I'm betting on a wrong scaling factor.

例如，如果我点击第一个单词，然后单击签名！"，这就是我得到的. :

For example, this is what I get if I tap the first word and then click "Sign !" :

所以这很准确.但是，如果我单击此PDF页面上的最后一个单词(即我的意思是页面，而不是本段)，则会发生这种情况:

So this is pretty accurate. however, this is what happens if I click the last word from this PDF page (and I mean page, not this paragraph) :

那根本不行.

有什么建议吗? 预先谢谢你

Any suggestion ? Thank you in advance

编辑

这是一段代码(您可以在github上找到)，上下文渲染将在其中启动，并且可能是我做错了的地方:

Here is a piece of code (that you can find on github) where the context rendering kicks in and might be the place I am doing it wrong :

// loop over PDF pages to render it
for(size_t page = 1; page <= numberOfPages; page++)
{
    //  Get the current page and page frame
    CGPDFPageRef pdfPage = CGPDFDocumentGetPage(pdf, page);
    const CGRect pageFrame = CGPDFPageGetBoxRect(pdfPage, kCGPDFMediaBox);

    UIGraphicsBeginPDFPageWithInfo(pageFrame, nil);

    //  Draw the page (flipped)
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGContextSaveGState(ctx);

    // Get appropriate scale
    //CGFloat scale = [[UIScreen mainScreen] scale];

    // As suggested in SO, the (1, -1) scale might need to be changed but couldn't get it right. Y axis is negative in order to render PDF (mandatory)
    CGContextScaleCTM(ctx, 1, -1);
    CGContextTranslateCTM(ctx, 0, -pageFrame.size.height);        
    CGContextDrawPDFPage(ctx, pdfPage);
    CGContextRestoreGState(ctx);

    if(page == 1)
    {
        [self drawLogo];
    }
}
UIGraphicsEndPDFContext();

推荐答案

您似乎没有为视网膜设备使用适当的比例尺.

It looks like you are not using the appropriate scale for retina devices.

ViewController.m

ViewController.m

CGContextScaleCTM(ctx, 1, -1);

这应该基于设备的规模.

This should be based off the device's scale.

例如(假设y比例值出于某种原因需要为负)

e.g. (Assuming the y scale value needs to be negative for some reason)

CGFloat scale = [[UIScreen mainScreen] scale]; 

CGContextScaleCTM(ctx, scale, -scale); 

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