--- title: HTMLCanvasElement.toDataURL() slug: Web/API/HTMLCanvasElement/toDataURL translation_of: Web/API/HTMLCanvasElement/toDataURL --- <div> <div> <div>{{APIRef("Canvas API")}}</div> </div> </div> <p><strong><code>HTMLCanvasElement.toDataURL()</code></strong> 方法返回一个包含图片展示的 <a href="/en-US/docs/Web/HTTP/data_URIs">data URI</a> 。可以使用 <code>type</code> 参数其类型,默认为 <a href="https://en.wikipedia.org/wiki/Portable_Network_Graphics">PNG</a> 格式。图片的分辨率为96dpi。</p> <ul> <li>如果画布的高度或宽度是0,那么会返回字符串“<code>data:,”。</code></li> <li>如果传入的类型非“<code>image/png</code>”,但是返回的值以“<code>data:image/png</code>”开头,那么该传入的类型是不支持的。</li> <li>Chrome支持“<code>image/webp</code>”类型。</li> </ul> <h2 id="Syntax" name="Syntax">语法</h2> <pre class="syntaxbox notranslate"><var><em>canvas</em>.toDataURL(<em>type</em>, <em>encoderOptions</em>);</var> </pre> <h3 id="参数">参数</h3> <dl> <dt><code>type</code> {{optional_inline}}</dt> <dd>图片格式,默认为 <code>image/png</code></dd> <dt><code>encoderOptions</code> {{optional_inline}}</dt> <dd>在指定图片格式为 <code>image/jpeg 或</code> <code>image/webp的情况下,可以从 0 到 1 的区间内选择图片的质量</code>。如果超出取值范围,将会使用默认值 <code>0.92</code>。其他参数会被忽略。</dd> </dl> <h3 id="返回值">返回值</h3> <p>包含 <a href="/en-US/docs/Web/HTTP/data_URIs">data URI</a> 的{{domxref("DOMString")}}。</p> <h2 id="示例">示例</h2> <p>有如下{{HTMLElement("canvas")}}元素</p> <pre class="brush: html notranslate"><canvas id="canvas" width="5" height="5"></canvas> </pre> <p>可以用这样的方式获取一个 data-URL</p> <pre class="brush: js notranslate">var canvas = document.getElementById("canvas"); var dataURL = canvas.toDataURL(); console.log(dataURL); // "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNby // blAAAADElEQVQImWNgoBMAAABpAAFEI8ARAAAAAElFTkSuQmCC" </pre> <h3 id="设置jpegs图片的质量">设置jpegs图片的质量</h3> <pre class="brush: js notranslate">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); </pre> <h3 id="Example_Dynamically_change_images" name="Example:_Dynamically_change_images">示例:动态更改图片</h3> <p>可以使用鼠标事件来动态改变图片(这个例子中改变图片灰度)。</p> <h4 id="HTML">HTML</h4> <pre class="brush: html notranslate"><img class="grayscale" src="myPicture.png" alt="Description of my picture" /></pre> <h4 id="JavaScript">JavaScript</h4> <pre class="brush: js;highlight:[33] notranslate">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); } }</pre> <h2 id="规范">规范</h2> <table class="standard-table"> <tbody> <tr> <th scope="col">规范</th> <th scope="col">状态</th> <th scope="col">备注</th> </tr> <tr> <td>{{SpecName('HTML WHATWG', "scripting.html#dom-canvas-todataurl", "HTMLCanvasElement.toDataURL")}}</td> <td>{{Spec2('HTML WHATWG')}}</td> <td>No change since the latest snapshot, {{SpecName('HTML5 W3C')}}</td> </tr> <tr> <td>{{SpecName('HTML5.1', "scripting-1.html#dom-canvas-todataurl", "HTMLCanvasElement.toDataURL")}}</td> <td>{{Spec2('HTML5.1')}}</td> <td></td> </tr> <tr> <td>{{SpecName('HTML5 W3C', "scripting-1.html#dom-canvas-todataurl", "HTMLCanvasElement.toDataURL")}}</td> <td>{{Spec2('HTML5 W3C')}}</td> <td>Snapshot of the {{SpecName('HTML WHATWG')}} containing the initial definition.</td> </tr> </tbody> </table> <h2 id="浏览器兼容性">浏览器兼容性</h2> <p>{{Compat("api.HTMLCanvasElement.toDataURL")}}</p> <div id="compat-desktop"></div> <h2 id="See_Also" name="See_Also">参考</h2> <ul> <li>定义接口,{{domxref("HTMLCanvasElement")}}</li> <li><a href="/en-US/docs/Web/HTTP">HTTP</a>引用中的<a href="/en-US/docs/Web/HTTP/data_URIs">Data URIs</a></li> </ul>