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This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

The HTMLCanvasElement.mozFetchAsStream() internal method used to create a new input stream that, when ready, would provide the contents of the canvas as image data. However, this non-standard and internal method has been removed.


void canvas.mozFetchAsStream(callback, type);


An nsIInputStreamCallback.
type Optional
A DOMString indicating the image format. The default type is image/png.

Return value



Save to disk with mozFetchAsStream (Chrome context only)

This technique also converts it to ico, however it will not work in Windows XP as WinXP cannot convert from PNG to ICO. It saves to the desktop it uses FileUtils.jsm. Also uses NetUtil.jsm

var canvas = document.getElementById('canvas');
var d = canvas.width;
ctx = canvas.getContext('2d');
ctx.moveTo(d / 2, 0);
ctx.lineTo(d, d);
ctx.lineTo(0, d);
ctx.fillStyle = 'yellow';

var netutilCallback = function() {
    return function(result) {
       if (!Components.isSuccessCode(result)) {               
          alert('FAILED to create icon');
       } else {
           alert('succesfully made');

var mfasCallback = function(iconName) {
    return function(inStream) {
       var file = FileUtils.getFile('Desk', [iconName + '.ico']);
       var outStream = FileUtils.openFileOutputStream(file);
       NetUtil.asyncCopy(inStream, outStream, netutilCallback());

canvas.mozFetchAsStream(mfasCallback('myIcon'), 'image/');


Not part of any specification.

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Chrome No support NoEdge No support NoFirefox No support 13 — 43IE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoEdge Mobile No support NoFirefox Android No support NoOpera Android No support NoSafari iOS No support NoSamsung Internet Android No support No


No support  
No support
Non-standard. Expect poor cross-browser support.
Non-standard. Expect poor cross-browser support.
Deprecated. Not for use in new websites.
Deprecated. Not for use in new websites.

See also

Schlagwörter des Dokuments und Mitwirkende

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