72 lines
2.4 KiB
Markdown
72 lines
2.4 KiB
Markdown
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---
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id: '2019-03-19-15-42'
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date: '2019-03-19-15-42'
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title: '纯html实现svg文件转png/jpg/bmp图片'
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tags: ['html', 'svg转换', 'png', 'jpg', 'bmp']
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categories:
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- '其他'
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---
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**本文原创发布于:**[www.tapme.top/blog/detail/2019-03-19-15-42](www.tapme.top/blog/detail/2019-03-19-15-42)
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**源码存放于：**[github](https://github.com/FleyX/demo-project/blob/master/%E6%9D%82%E9%A1%B9/1.svg%E8%BD%ACpng%E3%80%81jpg.html)
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  svg 文件实际上是一个 xml 文件，用于描述一个矢量图。可直接用浏览器打开，浏览器会自动解析为图片。但是有时候我们可能会需要将 svg 转成 png/jpeg 等图片格式，有什么简单易用的办法呢？
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  最简单的就是通过 html 来进行转换操作。主要流程如下：
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1. 使用`<input type='file'>`获取到文件信息
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```javascript
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let files = document.getElementById('file').files;
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```
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<!-- more -->
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2. 使用 html5 中的`FileReader`将文件内容读取出来
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```javascript
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for (let i = 0; i < files.length; i++) {
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let reader = new FileReader();
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reader.readAsText(files[i]);
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reader.onload = function(e) {
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arr.push({
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name: files[i].name,
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content: this.result
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});
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};
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}
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```
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3. 使用`DOMParser`解析 svg 内容
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```javascript
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let xml = new DOMParser().parseFromString(item.content, 'text/xml');
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let svgContent = xml.getElementsByTagName('svg')[0].outerHTML;
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```
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4. 将 svg 内容放到一个`Image`中,然后再将该 img 写入到 canvas 中,最后将 canvas 画布转为 data 字符串，使用`a`标签下载下来。
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```javascript
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let img = new Image();
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img.src = 'data:image/svg+xml;base64,' + window.btoa(unescape(encodeURIComponent(svgContent)));
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//这里要等img加载完毕再写到canvas中，否则canvas可能为空
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img.onload = function() {
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let canvas = document.getElementById('canvas');
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canvas.width = img.width;
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canvas.height = img.height;
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let ctx = canvas.getContext('2d');
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ctx.drawImage(img, 0, 0, img.width, img.height, 0, 0, img.width, img.height);
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//构建下载
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let a = document.createElement('a');
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a.href = canvas.toDataURL('image/' + postfix);
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a.download = item.name.substr(0, item.name.lastIndexOf('.')) + '.' + postfix;
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//调用点击开始下载
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a.click();
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};
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```
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# 效果如下
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