Multiple file,image upload


I am facing problem while selecting and uploading multiple images,file from gallery in android platform. I have to convert those selected images in base64 encoding and then pass the converted file to the web api service. While converting the selected images to base64 it shows me error as follows:

Failed to execute ‘readAsDataURL’ on ‘FileReader’: parameter 1 is not of type ‘Blob’.(…).

I am using window.imagePicker plugin for selecting the images.
Please help me out to resolve this issue as soon as possible.