The HTMLCanvasElement.toDataURL()
method returns a data URI containing a representation of the image in the format specified by the type
parameter (defaults to PNG). The returned image is in a resolution of 96 dpi.
- If the height or width of the canvas is
0
or larger than the maximum canvas size, the string"data:,"
is returned. - If the requested type is not
image/png
, but the returned value starts withdata:image/png
, then the requested type is not supported. - Chrome also supports the
image/webp
type.
Syntax
canvas.toDataURL(type, encoderOptions);
Parameters
type
Optional- A
DOMString
indicating the image format. The default format type isimage/png
. encoderOptions
Optional- A
Number
between0
and1
indicating the image quality to use for image formats that use lossy compression such asimage/jpeg
andimage/webp
.
If this argument is anything else, the default value for image quality is used. The default value is0.92
. Other arguments are ignored.
Return value
A DOMString
containing the requested data URI.
Exceptions
SecurityError
- The canvas's bitmap is not origin clean; at least some of its contents have or may have been loaded from a site other than the one from which the document itself was loaded.
Examples
Given this <canvas>
element:
<canvas id="canvas" width="5" height="5"></canvas>
You can get a data-URL of the canvas with the following lines:
var canvas = document.getElementById('canvas'); var dataURL = canvas.toDataURL(); console.log(dataURL); // "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNby // blAAAADElEQVQImWNgoBMAAABpAAFEI8ARAAAAAElFTkSuQmCC"
Setting image quality with jpegs
var fullQuality = canvas.toDataURL('image/jpeg', 1.0); // data:image/jpeg;base64,/9j/4AAQSkZJRgABAQ...9oADAMBAAIRAxEAPwD/AD/6AP/Z" var mediumQuality = canvas.toDataURL('image/jpeg', 0.5); var lowQuality = canvas.toDataURL('image/jpeg', 0.1);
Example: Dynamically change images
You can use this technique in coordination with mouse events in order to dynamically change images (gray-scale vs. color in this example):
HTML
<img class="grayscale" src="myPicture.png" alt="Description of my picture" />
JavaScript
window.addEventListener('load', removeColors); function showColorImg() { this.style.display = 'none'; this.nextSibling.style.display = 'inline'; } function showGrayImg() { this.previousSibling.style.display = 'inline'; this.style.display = 'none'; } function removeColors() { var aImages = document.getElementsByClassName('grayscale'), nImgsLen = aImages.length, oCanvas = document.createElement('canvas'), oCtx = oCanvas.getContext('2d'); for (var nWidth, nHeight, oImgData, oGrayImg, nPixel, aPix, nPixLen, nImgId = 0; nImgId < nImgsLen; nImgId++) { oColorImg = aImages[nImgId]; nWidth = oColorImg.offsetWidth; nHeight = oColorImg.offsetHeight; oCanvas.width = nWidth; oCanvas.height = nHeight; oCtx.drawImage(oColorImg, 0, 0); oImgData = oCtx.getImageData(0, 0, nWidth, nHeight); aPix = oImgData.data; nPixLen = aPix.length; for (nPixel = 0; nPixel < nPixLen; nPixel += 4) { aPix[nPixel + 2] = aPix[nPixel + 1] = aPix[nPixel] = (aPix[nPixel] + aPix[nPixel + 1] + aPix[nPixel + 2]) / 3; } oCtx.putImageData(oImgData, 0, 0); oGrayImg = new Image(); oGrayImg.src = oCanvas.toDataURL(); oGrayImg.onmouseover = showColorImg; oColorImg.onmouseout = showGrayImg; oCtx.clearRect(0, 0, nWidth, nHeight); oColorImg.style.display = "none"; oColorImg.parentNode.insertBefore(oGrayImg, oColorImg); } }
Specifications
Specification | Status | Comment |
---|---|---|
HTML Living Standard The definition of 'HTMLCanvasElement.toDataURL' in that specification. |
Living Standard | No change since the latest snapshot, HTML5 |
HTML 5.1 The definition of 'HTMLCanvasElement.toDataURL' in that specification. |
Recommendation | |
HTML5 The definition of 'HTMLCanvasElement.toDataURL' in that specification. |
Recommendation | Snapshot of the HTML Living Standard containing the initial definition. |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
toDataURL | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 2 | IE Full support 9 | Opera Full support 9 | Safari Full support 4 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 3.2 | Samsung Internet Android Full support 1.0 |
Legend
- Full support
- Full support
See also
- The interface defining it,
HTMLCanvasElement
. - Data URIs in the HTTP reference.