Chrome doesn't cache images inside SVG

Question

I just discovered that Chrome doesn't cache images which are placed inside SVGs if their cache-control header is set to no-cache. Firefox & IE10 seem to ignore this setting.

I've created a little test page with a static SVG:

HTML:

<div style="width: 500px; text-align: center;">
    <input id="move-left-btn" type="button" value="&lt;&lt;">
    <input id="move-right-btn" type="button" value="&gt;&gt;">
</div>

<div class="svgwrapper" style="width: 500px; height: 250px; background-color: lightgrey;">
    <svg id="svg" version="1.1" xmlns="http://www.w3.org/2000/svg" width="500" height="250">
        <g id="svggroup" class="transition-on" transform="matrix(0.2,0,0,0.2,80,35)">
            <image width="1672" height="887" opacity="1" xlink:href="https://dl.dropboxusercontent.com/sh/q7htlj5h8qqfhjf/SVDuynM7R3/car.png"></image>
        </g>
    </svg>
</div>

Javascript:

$(document).ready(function() {
    var curXPos = 80;

    // Local test function which represent some server calls in my "real life" scenario
    // Just updates the x-position in the transform matrix in this test case
    function updateSvgText(svgText, posXDelta) {
        curXPos += posXDelta;
        if (curXPos < 0) {
            curXPos = 160;
        } else if (curXPos > 160) {
            curXPos = 0;
        }

        return svgText.replace(/matrix\(.*\)/, 'matrix(0.2,0,0,0.2,' + curXPos + ',35)');
    }

    // Fetch the new SVG (in real life from server) and rerender it
    function moveSvg(posXDelta) {
        var svg = $('#svg'),
            svgText = updateSvgText($('.svgwrapper').html(), posXDelta);

        svg.empty();
        svg.append($(svgText).children());
    }

    $('#move-left-btn').click($.proxy(moveSvg, this, -20));
    $('#move-right-btn').click($.proxy(moveSvg, this, 20));
});

• Working example with cache-control header of source image set to no-cache (flickers in chrome after every press on the "move" buttons):
  http://jsfiddle.net/zF6NF/4/

• Same example with different source image with cache-control header set to max-age=315360000,public (no flickering):
  http://jsfiddle.net/zF6NF/5/

In Chrome you can see the reloading of the images on each button click in the first example ("flickering" of the image & visible in the network tab of the dev tools) whereas Firefox rerenders the SVG in both examples smoothly without any reloading.

Some additional information:

1. This is just an example. In my "real-life-scenario" I receive a new SVG from the server (instead of the updateSvgText method call) which means that I can't just perform partial updates of the SVG by changing the value of the transform matrix attribute but have to rerender the whole SVG every time (at least by now...).

2. I can't control where the images come from which means 2 things:

   • I can't change the cache-control header
   • I can't create Base64 encoded data-uris, save them locally and just replace the images inside the SVG with those data-uris before rendering (can't create Base64 encoded data-uri because of "Same resource origin" policies...)

Is there any way to either...

• Overwrite/overrule the cache-control header locally even if the image is from an uncontrolled remote location?
• Create the Base64 encoded data-uri from an Image that is loaded from a different domain I don't have any control over client sided?
• Somehow tell Chrome to always cache images inside my SVGs?

Needless to say that other solutions are also very welcome!

Thanks

Answer 1

Unfortunately, when it comes to caching, it's 99% the server's job.

In-dept guide : here

Browsers will always look for more recent versions of the file based on certain conditions:

• The cached entry has no expiration date and the content is being accessed for the first time in a browser session
• The cached entry has an expiration date but it has expired
• Cache-Control/Pragma tells the browser not to cache
• Etag in header is a pain.

In terms of solutions you have:

• Be very insistent to your server guys that you need caching (remove etag, Cache-Control: public,max-age=31536000, Pragma: public)
• Create a proxy on your domain that requires the image from the site, (optionally convert to base64) then send to your client (with the proper headers). Here's an example for PHP : here