/**
 * 图片压缩
 * imgSrc 地址
 * scale 压缩质量 0-1
 * type 文件类型
 */
export function compressImg  (imgSrc, scale, type, callback)  {
	// uni.$u.toast('压缩中')
	var img = new Image();
	img.src = imgSrc;
	img.onload = function() {
		var that = this;
		var h = (img.height * scale).toFixed(0); // 默认按质量比例压缩
		var w = (img.width * scale).toFixed(0);
		var canvas = document.createElement('canvas');
		var ctx = canvas.getContext('2d');
		var width = document.createAttribute("width");
		width.nodeValue = w;
		var height = document.createAttribute("height");
		height.nodeValue = h;
		canvas.setAttributeNode(width);
		canvas.setAttributeNode(height);
		ctx.drawImage(that, 0, 0, w, h);
		var base64 = canvas.toDataURL('image/jpeg', scale); //压缩比例
		canvas = null;
		if (type == 'base64') {
			let data = {
				size: getBase64Size(base64),
				type: type,
				source: base64
			}
			callback(base64);
		} else {
			let blob = base64ToBlob(base64);
			console.log('压缩后的大小', blob.size);
			const blobUrl = window.URL.createObjectURL(blob); //blob地址					
			blob.source = blobUrl
			callback(blob);
		}
	}
};
/**base转Blob */
export function base64ToBlob  (base64)  {
	var arr = base64.split(','),
		mime = arr[0].match(/:(.*?);/)[1],
		bstr = atob(arr[1]),
		n = bstr.length,
		u8arr = new Uint8Array(n);
	while (n--) {
		u8arr[n] = bstr.charCodeAt(n);
	}
	return new Blob([u8arr], {
		type: mime
	});
};
/**获取base64的文件大小 */
export function getBase64Size  () {
	let size = 0;
	if (base64Str) { // 获取base64图片byte大小
		const equalIndex = base64Str.indexOf('='); // 获取=号下标
		if (equalIndex > 0) {
			const str = base64Str.substring(0, equalIndex); // 去除=号
			const strLength = str.length;
			const fileLength = strLength - (strLength / 8) * 2; // 真实的图片byte大小
			size = Math.floor(fileLength); // 向下取整
		} else {
			const strLength = base64Str.length;
			const fileLength = strLength - (strLength / 8) * 2;
			size = Math.floor(fileLength); // 向下取整
		}
	} else {
		size = null;
	}
	return size
};