獲取本地上傳圖片、網絡圖片資源的base64編碼

1、獲取本地上傳圖片的base64編碼

var file = $_('upload_file').files[0];
var reader = new FileReader();
reader.readAsDataURL(file);
reader.onload = function (e) {
	imgBase64 = e.target.result;
};

點擊瞭解FileReader

2、獲取圖片資源的base64編碼

function getBase64Image(img,width,height) {//width、height調用時傳入具體像素值，控制大小 ,不傳則默認圖像大小
	var canvas = document.createElement("canvas");
	canvas.width = width ? width : img.width;
	canvas.height = height ? height : img.height;

	var ctx = canvas.getContext("2d");
	ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
	var dataURL = canvas.toDataURL();
	return dataURL;
}

var img = "https://img.alicdn.com/bao/uploaded/TB1qimQIpXXXXXbXFXXSutbFXXX.jpg"
var image = new Image();
image.crossOrigin = '';
image.src = img;
var deferred=$.Deferred();
if(img){
	image.onload =function (){
		deferred.resolve(getBase64Image(image));//將base64傳給done上傳處理
	}
	return deferred.promise();//問題要讓onload完成後再return sessionStorage['imgTest']
}