exam/exam-06173-uni/common/utils.js

/**
 * 图片压缩方法，压缩base64格式图片
 * @param {Object} base64
 * @param {Object} w
 */
function compressImage(base64, w) {

	return new Promise((resolve, reject) => {

		var img = new Image();
		var quality = 0.6; //压缩系数0-1之间
		img.src = base64;
		img.setAttribute("crossOrigin", 'Anonymous'); //url为外域时需要

		img.onload = function() {

			// 等比缩放
			let width = img.width;
			let height = img.height;
			console.log('++++orginal w：' + width + ',h:' + height)
			if (width > w) {
				const rate = height / width
				height = parseInt(w * rate)
				width = w
			}

			var canvas = document.createElement("canvas");
			var ctx = canvas.getContext("2d");
			canvas.width = width;
			canvas.height = height;
			quality = 0.8;

			console.log('++++compress w：' + width + ',h:' + height)

			ctx.clearRect(0, 0, canvas.width, canvas.height);
			ctx.drawImage(this, 0, 0, canvas.width, canvas.height);
			const base64 = canvas.toDataURL("image/jpeg", quality); //压缩语句
			resolve(base64);
		}

	})
}

module.exports = {
	compressImage: compressImage
}