This script allows you to take "screenshots" of webpages or parts of it, directly on the users browser. The screenshot is based on the DOM and as such may not be 100% accurate to the real representation as it does not make an actual screenshot, but builds the screenshot based on the information available on the page.
###How does it work?### The script renders the current page as a canvas image, by reading the DOM and the different styles applied to the elements.
It does not require any rendering from the server, as the whole image is created on the clients browser. However, as it is heavily dependent on the browser, this library is not suitable to be used on for example on node.js. It doesn't magically circumvent and browser content policy restrictions either, so rendering cross origin content will require a proxy to get the content to the same origin.
The script is still in a very experimental state, so I don't recommend using it in a production environment nor start building applications with it yet, as there will be still major changes made.
###Browser compatibility###
The script should work fine on the following browsers:
- Firefox 3.5+
- Google Chrome
- Opera 12+
- IE9+
As each CSS property needs to be manually built to be supported, there are a number of properties that are not yet supported.
To render an element with html2canvas, simply call:
html2canvas( [ element ], options);
To access the created canvas, provide the onrendered event in the options which returns the canvas element as the first argument, as such:
html2canvas( [ document.body ], {
onrendered: function(canvas) {
/* canvas is the actual canvas element,
to append it to the page call for example
document.body.appendChild( canvas );
*/
}
});
The library uses grunt for building. Alternatively, you can download the latest build from here.
Run the full build process (including lint, qunit and webdriver tests):
$ grunt
Skip lint and tests and simply build from source:
$ grunt build
The library has two sets of tests. The first set is a number of qunit tests that check that different values parsed by browsers are correctly converted in html2canvas. To run these tests with grunt you'll need phantomjs.
The other set of tests run Firefox, Chrome and Internet Explorer with webdriver. The selenium standalone server (runs on Java) is required for these tests and can be downloaded from here. They capture an actual screenshot from the test pages and compare the image to the screenshot created by html2canvas and calculate the percentage differences. These tests generally aren't expected to provide 100% matches, but while commiting changes, these should generally not go decrease from the baseline values.
Start by downloading the dependencies:
$ npm install
Run qunit tests:
$ grunt test
Run webdriver tests:
$ java -jar /path/to/selenium-server-standalone-2.xx.x.jar
$ grunt webdriver
Commiting improvements in baseline values:
$ grunt webdriver:baseline
For more information and examples, please visit the homepage or try the test console.
If you wish to contribute to the project, please send the pull requests to the develop branch. Before making any changes, make sure to run the webdriver tests to create the baseline results. If some CSS property isn't supported or is incomplete, please create appropriate tests for it as well before submitting any code changes.
v0.40 -
- Added rendering tests with webdriver
- Switched to using grunt for building
- Removed support for IE<9, including any FlashCanvas bits
- Support for border-radius
- Support for multiple background images, size, and clipping
- Support for :before and :after pseudo elements
- Support for placeholder rendering
- Reformatted all tests to small units to test specific features
v0.34 - 26.6.2012
- Removed (last?) jQuery dependencies (niklasvh)
- SVG-powered rendering (niklasvh)
- Radial gradients (SunboX)
- Split renderers to their own objects (niklasvh)
- Simplified API, cleaned up code (niklasvh)
v0.33 - 2.3.2012
- SVG taint fix, and additional taint testing options for rendering (niklasvh)
- Added support for CORS images and option to create canvas as tainted (niklasvh)
- Improved minification saved ~1K! (cobexer)
- Added integrated support for Flashcanvas (niklasvh)
- Fixed a variety of legacy IE bugs (niklasvh)
v0.32 - 20.2.2012