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What is the best way to generate image data from the contents of an HTML canvas element?
I'd like to create the image data such that it can be transmitted to a server (it's not necessary for the user to be able to directly save to a file). The image data should be in a common format such as PNG or JPEG.
Solutions that work correctly in multiple browsers are preferred, but if every solution depends on the browser, recent versions of Firefox should be targeted.
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The getImageData() method returns an ImageData object that copies the pixel data for the specified rectangle on a canvas. Note: The ImageData object is not a picture, it specifies a part (rectangle) on the canvas, and holds information of every pixel inside that rectangle.
function convertCanvasToImage() { let canvas = document. getElementById("canvas"); let image = new Image(); image. src = canvas. toDataURL(); return image; } let pnGImage = convertCanvasToImage(); document.
toDataURL() method returns a data URL containing a representation of the image in the format specified by the type parameter. The desired file format and image quality may be specified. If the file format is not specified, or if the given format is not supported, then the data will be exported as image/png .
The canvas in HTML5 has a method called toDataURL() that you can call to turn a HTML5 canvas into a PNG image and to get the image data of that canvas. By default it will give you a base64 representation of the image in PNG format. In simpler terms, you will get a PNG image but it has been encoded in base64.
Firefox and Opera have a toDataURL() method that returns a data-URL formatted PNG. You can assign the result to a form field to submit it to the server.
The data URL is base-64 encoded, so you will have to decode it on the server side. You would also need to strip off the "data:image/png;" part of course.
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I think a lib you can use is Canvas2Image, it uses native features from Canvas, but it won't work on any browser. I have an optimized version of this lib, if you want to, I'll share it with you.
Then you could get the generated Data URI and send it using Ajax to the server.
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