export function compress(fileObj, callback) {
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try {
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const image = new Image();
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image.src = URL.createObjectURL(fileObj);
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image.onload = function() {
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const that = this;
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// 默认按比例压缩
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let w = that.width;
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let h = that.height;
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const scale = w / h;
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w = fileObj.width || w;
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h = fileObj.height || w / scale;
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let quality = 0.7; // 默认图片质量为0.7
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// 生成canvas
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const canvas = document.createElement("canvas");
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const ctx = canvas.getContext("2d");
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// 创建属性节点
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const anw = document.createAttribute("width");
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anw.nodeValue = w;
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const anh = document.createAttribute("height");
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anh.nodeValue = h;
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canvas.setAttributeNode(anw);
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canvas.setAttributeNode(anh);
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ctx.drawImage(that, 0, 0, w, h);
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// 图像质量
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if (fileObj.quality && fileObj.quality <= 1 && fileObj.quality > 0) {
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quality = fileObj.quality;
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}
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// quality值越小，所绘制出的图像越模糊
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const data = canvas.toDataURL("image/jpeg", quality);
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// 压缩完成执行回调
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const newFile = convertBase64UrlToBlob(data);
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callback(newFile);
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};
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} catch (e) {
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console.log("压缩失败!");
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}
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}
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function convertBase64UrlToBlob(urlData) {
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const bytes = window.atob(urlData.split(",")[1]); // 去掉url的头，并转换为byte
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// 处理异常,将ascii码小于0的转换为大于0
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const ab = new ArrayBuffer(bytes.length);
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const ia = new Uint8Array(ab);
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for (let i = 0; i < bytes.length; i++) {
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ia[i] = bytes.charCodeAt(i);
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}
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return new Blob([ab], { type: "image/png" });
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}
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