November 2011
Intermediate to advanced
348 pages
7h 2m
English
Content preview from HTML5 Canvas CookbookBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Appendix B. Canvas Security
In order to protect pixel data of images, videos, and canvases on your website, the HTML5 canvas specification has safeguards in place to prevent scripts from other domains from accessing these media, manipulating them, and then creating new images, videos, or canvases.
Before anything is drawn on the canvas, the canvas tag has an origin-clean flag that's set to true. This basically means that the canvas is "clean". If you draw an image onto the canvas that's hosted on the same domain as the code running it, the origin-clean flag remains true. If, however, you draw an image onto the canvas that's hosted on another domain, the origin-clean flag is set to false and the canvas is now "dirty".
According to the HTML5 canvas ...
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