html2canvas missing background

问题

I am using html2canvas to generate image from my html page.

When I enter my url http://prompter.rareapps.org/prompt/prompt-save2.php?p=123

in webpage renderer of html2canvas website (http://html2canvas.hertzen.com/screenshots.html) my page is rendered corectly with background.

But when I generate my own canvas, I do not have the background. Here is my code

<script type="text/javascript">
$( document ).ready(function() {
    html2canvas(document.body, {
        allowTaint: true,
        taintTest: false,
        onrendered: function(canvas) {
        window.location.href = canvas.toDataURL('image/jpeg');
      }
    });
});

What did I miss?

Thanks

回答1:

This problem is fixed in 0.5.0 version (But version 0.5.0 is not yet ready for use).

But have a lot of problems that are being corrected and basic functions that have not yet been implemented.

Note: html2canvas has no date forecast for 0.5.0 release Note: version 0.4.1 no longer receives updates

The problem is that version 0.5.0 is not ready for use, I reworked your html, see:

<!DOCTYPE html><!--// Never put a space/break-line before the DOCTYPE -->
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <meta charset="UTF-8">

    <script type="text/javascript" src="html2canvas.js"></script>
    <script type="text/javascript" src="https://code.jquery.com/jquery-1.11.0.min.js"></script>

    <style type="text/css">
        html, body {
            margin: 0;
            padding: 0;
            height: 100%;
        }
        body {
            font-family: Georgia, serif;
            font-size: 4em;
        }
        p {
            padding: 5px 0;
            margin: 0;
        }

        #main {
            margin: 0 auto;
            width: 100%;
            min-height: 100%;
            font-weight: bold;
            background: white url('prompt-save-bg.jpg') center top repeat-y;
            max-width: 1263px; /* background-limit*/
            text-align: center;
        }
        #article {
            padding: 5em 2em 0 2em;
            font-weight: bold;
        }
        #article p.info {
            font-size: 0.2em; padding: 40em 0;
        }
    </style>

    <script type="text/javascript">
    //<!CDATA[
    function save(canvas) {/*html2canvas-0.5.0 work with Promise.js*/
        window.open(canvas.toDataURL());
    }
    $(document).ready(function(){
        $('#save-image').click(function () {
            html2canvas(document.body, {
                allowTaint: true,
                logging: true,
                taintTest: false,
                onrendered: save /*0.4.1*/
            }).then(save);/*0.5.0-rc*/
        });
    });
    //]]>
    </script>
</head>
<body>
    <div id="main">
        <input value="Generate Image" id="save-image" download="YourFileName.jpg" type="button">

        <div id="article">
            <h2>AUBREY</h2>

            <p>And Aubrey was her name</p>
            <p>A not so very ordinary girl or name</p>
            <p>But who's to blame?</p>
            <p>For a love that wouldn't bloom</p>
            <p>For the hearts that never played in tune</p>
            <p>Like a lovely melody that everyone can sing</p>
            <p>Take away the words that rhyme, it doesn't mean a thing</p>
            <p>&nbsp;</p>
            <p>And Aubrey was her name</p>
            <p>We tripped the light and danced together to the moon</p>
            <p>But where was June?</p>
            <p>No, it never came around</p>
            <p>If it did it never made a sound</p>
            <p>Maybe I was absent or was listening too fast</p>
            <p>Catching all the words but then the meaning going past</p>
            <p>&nbsp;</p>
            <p>But God I miss the girl</p>
            <p>And I'd go a thousand times around the world just to be</p>
            <p>Closer to her than to me</p>
            <p>&nbsp;</p>
            <p>And Aubrey was her name</p>
            <p>I never knew her but I loved her just the same</p>
            <p>I loved her name</p>
            <p>Wish that I had found the way</p>
            <p>And the reasons that would make her stay</p>
            <p>I have learned to lead a life apart from all the rest</p>
            <p>If I can't have the one I want, I'll do without the best</p>
            <p>&nbsp;</p>
            <p>But how I miss the girl</p>
            <p>And I'd go a million times around the world just to say</p>
            <p>She had been mine for a day</p>

            <p class="info">
                Prompter generated by RAREAPPS: http://prompter.rareapps.org
            </p>
        </div>
    </div>
</body>
</html>

Worked in 0.4.1 and 0.5.0-rc.
Worked in Chrome and Firefox.

Note that I created a function called save(), so you can switch between onrendered (version 0.4.1) or then (version 0.5.0-rc).

I put your background and a <DIV> not changed the <html> and not the <body> because the "html2canvas" is not smart enough to understand the manipulations of overflow: in the window.

Note that the margin:; in your last paragraph (<p>) caused problems both in "html2canvas" as in "Webkit" browser so I used padding:

Remember there is more than one way to do the same thing.

回答2:

explicitly set a background style Eg. if

...
 html2canvas(document.body,
        {
            onrendered: function(canvas){
                 var imgData = canvas.toDataURL("image/jpeg");
                var doc = new jsPDF('p','mm');
                doc.addImage(imgData, 'JPEG', 15, 40, 180, 160);
                doc.save($.now()+'.pdf');
        }

the pdf has blank (black) background,

now if you add CSS style

 body {
         background-color: white;
     }

the blank (black) background is corrected

回答3:

There is a problem with background images whose background-size attributes are set as cover in 0.4.1 version which is the latest version currently available.

The solution provided from 'fperich' in this page solved my problem: https://github.com/niklasvh/html2canvas/issues/265

According to his solution, just update line 350 in the version 0.4.1 with the following statement:

topPos = isNaN(parseInt(bgposition[1], 10)) ? topPos : parseInt(bgposition[1], 10);

来源：https://stackoverflow.com/questions/22569210/html2canvas-missing-background

标签

html

background-image

html2canvas