HTMLCanvasElement.toDataURL()
方法返回
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.
0
or larger than the
maximum canvas size
，字符串
"data:,"
被返回。
image/png
, but the returned value starts with
data:image/png
, then the requested type is not supported.
image/webp
类型。
canvas.toDataURL(type, encoderOptions);
type
可选
DOMString
indicating the image format. The default format type is
image/png
.
encoderOptions
可选
Number
between
0
and
1
indicating the image quality to use for image formats that use lossy compression such as
image/jpeg
and
image/webp
.
0.92
. Other arguments are ignored.
A
DOMString
containing the requested
data URI
.
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.
Given this
<canvas>
元素：
<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"
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);
You can use this technique in coordination with mouse events in order to dynamically change images (gray-scale vs. color in this example):
<img class="grayscale" src="myPicture.png" alt="Description of my picture" />
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);
}
}
| 规范 | 状态 | 注释 |
|---|---|---|
|
HTML 实时标准
The definition of 'HTMLCanvasElement.toDataURL' in that specification. |
实时标准 | 无变化从最新快照起， HTML5 |
|
HTML 5.1
The definition of 'HTMLCanvasElement.toDataURL' in that specification. |
推荐 | |
|
HTML5
The definition of 'HTMLCanvasElement.toDataURL' in that specification. |
推荐 | Snapshot of the HTML 实时标准 containing the initial definition. |
| 桌面 | 移动 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
toDataURL
|
Chrome 1 | Edge 12 | Firefox 2 | IE 9 | Opera 9 | Safari 4 | WebView Android 1 | Chrome Android 18 | Firefox Android 4 | Opera Android 10.1 | Safari iOS 3.2 | Samsung Internet Android 1.0 |
完整支持
HTMLCanvasElement
.