图片转Base64（FileBridge.image2Base64)

//成功回调
var onSuccess = function(message){
    alert(message);
}

//失败回调
var onError = function(message){
    alert(message);
}

//调用方法
function image2Base64(){
    var options = {
    	"filePath":"xxxxxxxx",
    	"quality":50,//取值范围0-100  100时图片不压缩
	}
	var arguments = {
    	className:"FileBridge",
    	function:"image2Base64",
    	params:options,
    	successCallBack:"onSuccess",
    	failCallBack:"onError"
	}
	HandBridge.postMessage(JSON.stringify(arguments));
}