小学学校网站建设计划,在线阅读小说网站开发,建设境外网站需要什么手续,电商平台规则各种报名都对照片有大小限制#xff0c;鉴于这种情况#xff0c;网上搜了后拼凑出了如下代码#xff0c;用于解决1寸照片修改为2寸照片#xff0c;同时将DPI修改为300#xff0c;当然也可以根据自己的情况修改代码#xff1a;
HTML
input typefile id鉴于这种情况网上搜了后拼凑出了如下代码用于解决1寸照片修改为2寸照片同时将DPI修改为300当然也可以根据自己的情况修改代码
HTML
input typefile idinput acceptimage/*
div styledisplay: grid;grid-template-columns: 1fr 5px 1fr;divp修改前/pimg idbefore-image src styledisplay: block; max-width:100%; /divdiv/divdivp修改后点击图片下载/pa hrefjavascript:; downloadimg idafter-image src styledisplay: block;/a/div
/divJS
script typetext/javascriptconst after_image document.getElementById(before-image);document.getElementById(input).addEventListener(change, (e) {const reader new FileReader();reader.readAsDataURL(e.target.files[0]);reader.onload (e) {b64 e.target.result;after_image.src b64;//设置目标图片大小var target_width 413;var target_height 626;//计算目标图片宽高比例var target_wh_scale target_width / target_height;//定义一个Image对象var bitmap new Image();bitmap.src b64;bitmap.onload function () {//var cut_width 0;var cut_height 0;//var bitmap_wh_scale bitmap.width / bitmap.height;if (bitmap_wh_scale target_wh_scale) {cut_width bitmap.width - bitmap.width / (bitmap_wh_scale / target_wh_scale);}//裁剪宽度else if (bitmap_wh_scale target_wh_scale) {cut_height bitmap.height - bitmap.height * (bitmap_wh_scale / target_wh_scale);} else {Console.log(比例一致无需裁剪);}console.log(图片裁剪宽度 cut_width px);console.log(图片裁剪高度 cut_height px);const canvas document.createElement(canvas);const ctx canvas.getContext(2d);canvas.width target_width;canvas.height target_height;ctx.drawImage(this, cut_width / 2, cut_height / 2, bitmap.width - cut_width, bitmap.height - cut_height, 0, 0, target_width, target_height);var after_img document.getElementById(after-image);after_img.src canvas.toDataURL(image/jpg);var dataUrl canvas.toDataURL(image/jpeg, 0.9);//修改DPI为300downloadBase64Img(after_img.parentElement, changeDpiDataUrl(dataUrl, 300), t.jpg);}};})function downloadBase64Img(a, base64URL, fileName) {// 将 a 标签的 download 属性设置为要下载的文件名a.download fileName || image;// 创建 Blob 对象并获取 base64 数据的 MIME 类型const mimeType base64URL.match(/:(.*?);/)[1];// 将 base64 数据转换为字节数组const byteCharacters atob(base64URL.split(,)[1]);const byteNumbers new Array(byteCharacters.length);// 将字节数组填充到 Uint8Array 中for (let i 0; i byteCharacters.length; i) {byteNumbers[i] byteCharacters.charCodeAt(i);}const byteArray new Uint8Array(byteNumbers);// 创建 Blob 对象const blob new Blob([byteArray], { type: mimeType });// 将 Blob 对象的 URL 赋值给 a 标签的 href 属性a.href URL.createObjectURL(blob);}function changeDpiDataUrl(base64Image, dpi) {const PNG image/png;const JPEG image/jpeg;const dataSplitted base64Image.split(,);const format dataSplitted[0];const body dataSplitted[1];let type;let headerLength;let overwritepHYs false;if (format.indexOf(PNG) ! -1) {type PNG;const b64Index detectPhysChunkFromDataUrl(body);// 28 bytes in dataUrl are 21bytes, length of phys chunk with everything inside.if (b64Index 0) {headerLength Math.ceil((b64Index 28) / 3) * 4;overwritepHYs true;} else {headerLength 33 / 3 * 4;}}if (format.indexOf(JPEG) ! -1) {type JPEG;headerLength 18 / 3 * 4;}// 33 bytes are ok for pngs and jpegs// to contain the information.const stringHeader body.substring(0, headerLength);const restOfData body.substring(headerLength);const headerBytes atob(stringHeader);const dataArray new Uint8Array(headerBytes.length);for (let i 0; i dataArray.length; i) {dataArray[i] headerBytes.charCodeAt(i);}const finalArray changeDpiOnArray(dataArray, dpi, type, overwritepHYs);const base64Header btoa(String.fromCharCode(...finalArray));return [format, ,, base64Header, restOfData].join();}function changeDpiOnArray(dataArray, dpi, format, overwritepHYs) {const PNG image/png;const JPEG image/jpeg;if (format JPEG) {dataArray[13] 1; // 1 pixel per inch or 2 pixel per cmdataArray[14] dpi 8; // dpiX high bytedataArray[15] dpi 0xff; // dpiX low bytedataArray[16] dpi 8; // dpiY high bytedataArray[17] dpi 0xff; // dpiY low bytereturn dataArray;}if (format PNG) {const physChunk new Uint8Array(13);// chunk header pHYs// 9 bytes of data// 4 bytes of crc// this multiplication is because the standard is dpi per meter.const _P p.charCodeAt(0);const _H H.charCodeAt(0);const _Y Y.charCodeAt(0);const _S s.charCodeAt(0);dpi * 39.3701;physChunk[0] _P;physChunk[1] _H;physChunk[2] _Y;physChunk[3] _S;physChunk[4] dpi 24; // dpiX highest bytephysChunk[5] dpi 16; // dpiX veryhigh bytephysChunk[6] dpi 8; // dpiX high bytephysChunk[7] dpi 0xff; // dpiX low bytephysChunk[8] physChunk[4]; // dpiY highest bytephysChunk[9] physChunk[5]; // dpiY veryhigh bytephysChunk[10] physChunk[6]; // dpiY high bytephysChunk[11] physChunk[7]; // dpiY low bytephysChunk[12] 1; // dot per meter....const crc calcCrc(physChunk);const crcChunk new Uint8Array(4);crcChunk[0] crc 24;crcChunk[1] crc 16;crcChunk[2] crc 8;crcChunk[3] crc 0xff;if (overwritepHYs) {const startingIndex searchStartOfPhys(dataArray);dataArray.set(physChunk, startingIndex);dataArray.set(crcChunk, startingIndex 13);return dataArray;} else {// i need to give back an array of data that is divisible by 3 so that// dataurl encoding gives me integers, for luck this chunk is 17 4 21// if it was we could add a text chunk contaning some info, untill desired// length is met.// chunk structur 4 bytes for length is 9const chunkLength new Uint8Array(4);chunkLength[0] 0;chunkLength[1] 0;chunkLength[2] 0;chunkLength[3] 9;const finalHeader new Uint8Array(54);finalHeader.set(dataArray, 0);finalHeader.set(chunkLength, 33);finalHeader.set(physChunk, 37);finalHeader.set(crcChunk, 50);return finalHeader;}}}
/script以上代码中changeDpiDataUrl()和changeDpiOnArray()两个函数来源于开源项目changeDPI。
