canvas绘制网络地址图片

canvas在绘制网络地址图片时，需要先下载成临时路径

export function downLoadBgImg (url) {
	return new Promise((r,j) => {
		uni.downloadFile({
			url,
			success : res => {
				if (res.statusCode === 200) {
					r(res.tempFilePath);
					return;
				};
				j('依赖文件下载失败');
			},
			fail : err => {
				j(err)
			}
		})
	})
}

需要用到的地方

import { downLoadBgImg } from '@/js/share.js';
shareInit(){
	const ctx = uni.createCanvasContext('share-canvas', this);
	return new Promise(async(r,j)=>{
		try{
			let bgImgUrl = await downLoadBgImg(...);
			ctx.drawImage(bgImgUrl,0,0,uni.upx2px(600),uni.upx2px(480))
		}catch(e){
			j(e);
		}
	})
}