O'Reilly

Cross Domain Canvas Images

By on  

You can do some really awesome stuff with images when you push their data into canvas.  And of course, when you're done playing around with the image, you can export the canvas data to an IMG element and data URI.  What we sometimes don't remember, however, is that the cross-origin rules apply to those images, so if you try to convert an image from another host to canvas, you'll get an error.  You can use this snippet from HTML5 Boilerplate within the image host domain's .htaccess file to allow cross-origin data reading of images:

<IfModule mod_setenvif.c>
	<IfModule mod_headers.c>
		<FilesMatch "\.(cur|gif|ico|jpe?g|png|svgz?|webp)$">
			SetEnvIf Origin ":" IS_CORS
			Header set Access-Control-Allow-Origin "*" env=IS_CORS
		</FilesMatch>
	</IfModule>
</IfModule>

Allowing for CORS within .htaccess then allows you to pull image data when the image is on another domain. This is especially useful on CDNs! .htaccess is a life-saver sometimes!

Treehouse Learning

Recent Features

  • Responsive Images: The Ultimate Guide

    Chances are that any Web designers using our Ghostlab browser testing app, which allows seamless testing across all devices simultaneously, will have worked with responsive design in some shape or form. And as today’s websites and devices become ever more varied, a plethora of responsive images...

  • Create a Sheen Logo Effect with CSS

    I was inspired when I first saw Addy Osmani's original ShineTime blog post.  The hover sheen effect is simple but awesome.  When I started my blog redesign, I really wanted to use a sheen effect with my logo.  Using two HTML elements and...

Incredible Demos

  • MooTools HTML Police: dwMarkupMarine

    We've all inherited rubbish websites from webmasters that couldn't master valid HTML. You know the horrid markup: paragraph tags with align attributes and body tags with background attributes. It's almost a sin what they do. That's where dwMarkupMarine comes in....

  • jQuery Random Link Color Animations

    We all know that we can set a link's :hover color, but what if we want to add a bit more dynamism and flair? jQuery allows you to not only animate to a specified color, but also allows you to animate to a random color. The...

Discussion

    Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!