72 lines
2.5 KiB
JavaScript
72 lines
2.5 KiB
JavaScript
/**
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* 图片压缩
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* imgSrc 地址
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* scale 压缩质量 0-1
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* type 文件类型
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*/
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export async function H5compressImg(imgSrc, scale) {
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//imgSrc:图片的路径
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//scale:缩放比例 0-1之间
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return new Promise((reslove, reject) => {
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var img = new Image(); //创建Image对象生成一个<img>标签
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img.src = imgSrc; //将图片路径赋给<img>标签的src
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img.onload = () => {
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//onload在图片加载成功后触发，在onload中完成压缩功能
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var h = img.height / 2; // 获取原本图片的宽高
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var w = img.width / 2; //默认按比例压缩,根据需求修改
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var canvas = document.createElement("canvas"); //创建画布
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var ctx = canvas.getContext("2d"); //设置为2d效果
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var width = document.createAttribute("width"); //创建属性节点
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width.nodeValue = w; //设置属性值
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var height = document.createAttribute("height");
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height.nodeValue = h;
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canvas.setAttributeNode(width); //设置画布宽高
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canvas.setAttributeNode(height);
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ctx.drawImage(img, 0, 0, w, h); //将图片贴到画布上
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//img:图片 0,0:粘贴的位置 w,h:粘贴图片的大小
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var base64 = canvas.toDataURL("image/png", scale);
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//'image/png':压缩返回图片的类型 scale:图片质量
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//如果要base64的流，可以直接将结果返回了
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canvas = null; //清除画布
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// var blob = base64ToBlob(base64); //需要二进制流调用该方法拿到
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// let blobUrl = window.URL.createObjectURL(blob); //blob地址
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reslove(base64);
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};
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});
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}
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/**base转Blob */
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export function base64ToBlob(base64) {
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var arr = base64.split(","),
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mime = arr[0].match(/:(.*?);/)[1],
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bstr = atob(arr[1]),
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n = bstr.length,
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u8arr = new Uint8Array(n);
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while (n--) {
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u8arr[n] = bstr.charCodeAt(n);
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}
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return new Blob([u8arr], {
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type: mime,
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});
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}
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/**获取base64的文件大小 */
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export function getBase64Size(base64Str) {
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let size = 0;
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if (base64Str) {
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// 获取base64图片byte大小
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const equalIndex = base64Str.indexOf("="); // 获取=号下标
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if (equalIndex > 0) {
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const str = base64Str.substring(0, equalIndex); // 去除=号
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const strLength = str.length;
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const fileLength = strLength - (strLength / 8) * 2; // 真实的图片byte大小
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size = Math.floor(fileLength); // 向下取整
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} else {
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const strLength = base64Str.length;
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const fileLength = strLength - (strLength / 8) * 2;
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size = Math.floor(fileLength); // 向下取整
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}
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} else {
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size = null;
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}
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return size;
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}
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