使用pdf.js显示透明背景的pdf

我有一个4页的pdf,每个页面都有一个透明的背景 . 我使用pdf.js来显示它们,但我想在我的html页面上用透明背景显示它们但我无法弄清楚我是如何做到的,总是有一个白色背景:

example

我认为根据this issue是可能的,但是当我将行 page.render(renderContext); 更改为 page.render({renderContext, viewport, backgroundColor: 'rgba(0,0,0,0)' }); 时(正如它在问题中所述)我有以下错误:

enter image description here

关于如何管理它的任何想法?

我使用pdf.js版本v1.9.426和Firefox 55.0.2(64位) .

EDIT : 使用以下代码我在控制台中没有错误,但我的pdf文件的背景仍为白色 . (但是,如果用例如photoshop打开pdf则没有背景)

链接到我使用的PDF文件:tempPDF.pdf

这是我的javascript文件,显示四个页面:

var pdfFile;
PDFJS.getDocument('/assets/pdf/tempPDF.pdf').then(function (pdf) {
    pdfFile = pdf;

    for(var i = 1; i <= 5; i++) {
        var canvas = document.getElementById('canvas'+i);
        var context = canvas.getContext('2d');
        PDFJS.disableStream = true;
        openPage(pdf, i, context, 50);
    }
});

function openPage(pdfFile, pageNumber, context, ratio) {
    var scale = 10;
    pdfFile.getPage(pageNumber).then(function (page) {
        viewport = page.getViewport(scale);
        // reference canvas via context
        var canvas = context.canvas;
        canvas.width = viewport.width;
        canvas.height = viewport.height;
        canvas.style.width = ratio+"%";
        canvas.style.height = ratio+"%";
        var renderContext = {
            canvasContext: context
            , viewport: viewport
        };
        page.render({canvasContext: context, viewport: viewport, backgroundColor: 'rgba(0,0,0,0)' });
        //page.render(renderContext);
    });
}

我的html页面可能有用:

<!DOCTYPE html>
<html>
<body
        style="background-color:powderblue;">
</body>
<head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">
    <meta name="description" content="PDF Viewer" />
    <title>My page</title>
</head>
<body>
    <form action="pdf_latex_test.php">
        <input type="submit" value="execute" /> </form>
</body>
<body>
    <canvas id="canvas1" width="300" height="300"></canvas>
    <canvas id="canvas2" width="300" height="300"></canvas>
    <canvas id="canvas3" width="300" height="300"></canvas>
    <canvas id="canvas4" width="300" height="300"></canvas>
<script src="/assets/js/pdf.js"></script>
<script src="/assets/js/pdf.worker.js"></script>
<script src="/assets/js/pdf.latex.main.js"></script>
</body>
</html>

回答(1)

2 years ago

changeAPI documentation显示属性名称必须为 background

var url = '//cdn.mozilla.net/pdfjs/helloworld.pdf';

PDFJS.workerSrc = '//mozilla.github.io/pdf.js/build/pdf.worker.js';

var loadingTask = PDFJS.getDocument(url);
loadingTask.promise.then(function(pdf) {
  var pageNumber = 1;
  pdf.getPage(pageNumber).then(function(page) {
    console.log('Page loaded');
    
    var scale = 1.5;
    var viewport = page.getViewport(scale);

    // Prepare canvas using PDF page dimensions
    var canvas = document.getElementById('the-canvas');
    var context = canvas.getContext('2d');
    canvas.height = viewport.height;
    canvas.width = viewport.width;

    // Render PDF page into canvas context
    var renderContext = {
      canvasContext: context,
      // Use transparent background!
      background: 'rgba(0,0,0,0)',
      viewport: viewport
    };
    var renderTask = page.render(renderContext);
    renderTask.then(function () {
      console.log('Page rendered');
    });
  });
}, function (reason) {
  // PDF loading error
  console.error(reason);
});
#the-canvas {
  border:1px solid black;
  background-image: url(http://image.blingee.com/images19/content/output/000/000/000/7c8/805674825_1628628.gif?6);
}
<script src="//mozilla.github.io/pdf.js/build/pdf.js"></script>
<canvas id="the-canvas"></canvas>