圖檔壓縮（基于圖檔寬度）

function dealImage (base64,w) {

//壓縮base64方法

var newImage = new Image();

var quality = 0.6; //壓縮系數0-1之間

newImage.src = base64;

newImage.setAttribute(“crossOrigin”, ‘Anonymous’); //url為外域時需要

var imgWidth, imgHeight;

newImage.onload = function () {

imgWidth = this.width;

imgHeight = this.height;

var canvas = document.createElement(“canvas”);

var ctx = canvas.getContext(“2d”);

if (Math.max(imgWidth, imgHeight) > w) {

if (imgWidth > imgHeight) {

canvas.width = w;

canvas.height = w * imgHeight / imgWidth;

} else {

canvas.height = w;

canvas.width = w * imgWidth / imgHeight;

}

} else {

canvas.width = imgWidth;

canvas.height = imgHeight;

quality = 0.6;

}

ctx.clearRect(0, 0, canvas.width, canvas.height);

ctx.drawImage(this, 0, 0, canvas.width, canvas.height);

var base64 = canvas.toDataURL(“image/jpeg/*”, quality); //壓縮語句

console.log(base64);

return base64;

}

},

使用的時候直接調用該函數：dealImage （”這個傳遞汲取一個圖檔base64“，”這個傳遞圖檔寬度我一般傳1000“）；函數會将壓縮過的base64直接傳回出來