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JS压缩图片并转换base64

残北 2022-04-21 阅读 92
javascript

JS压缩图片并转换base64

// 调用
photoCompress(pic, 1080, 0, 0.3, function(base64Codes, path) {
		Base64Url = base64Codes;
		appendFile(pic);
});


/*
三个参数
file:一个是文件(类型是图片格式),
w:一个是文件压缩的后宽度,宽度越小,字节越小
objDiv:一个是容器或者回调函数
photoCompress()
 */
// 图片压缩的方法
// file:通过file控件上传的图片文件
// w: 图片宽度,0表示根据高度按比例
// h: 图片高度,0表示根据宽度按比例
// objDiv:回调函数
function photoCompress(file, w, h, qua, callback) {
	var obj = {
		width: w,
		height: h,
		quality: qua
	}
	if (w == 0) {
		obj = {
			height: h,
			quality: qua
		}
	} else if (h == 0) {
		obj = {
			width: w,
			quality: qua
		}
	}
	canvasDataURL(file, obj, callback);
}
// path:需要压缩的Base64图片
function canvasDataURL(path, obj, callback) {
	var img = new Image();
	img.src = path;
	img.crossOrigin = "anonymous"; //关键
	img.onload = function() {
		var that = this;
		// 默认按比例压缩
		var w = that.width,
			h = that.height,
			scale = w / h;
		//alert(h)
		w = obj.width || w;
		h = obj.height || (w / scale);
		//alert(h)
		var quality = 0.7; // 默认图片质量为0.7
		//生成canvas
		var canvas = document.createElement('canvas');
		var ctx = canvas.getContext('2d');
		// 创建属性节点
		var anw = document.createAttribute("width");
		anw.nodeValue = w;
		var anh = document.createAttribute("height");
		anh.nodeValue = h;
		canvas.setAttributeNode(anw);
		canvas.setAttributeNode(anh);
		ctx.drawImage(that, 0, 0, w, h);
		// 图像质量
		if (obj.quality && obj.quality <= 1 && obj.quality > 0) {
			quality = obj.quality;
		}
		var base64 = canvas.toDataURL('image/jpeg', quality);
		// 回调函数返回base64的值
		callback(base64, path);
	}
}
/*** 根据图片生成画布*/
function convertImageToCanvas(image) {
	var canvas = document.createElement("canvas");
	canvas.width = image.width;
	canvas.height = image.height;
	canvas.getContext("2d").drawImage(image, 0, 0);
	return canvas;
}
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