Change Position options from Radio Button to Dropdown selection and Image Size

[slimshadddyyy]

Integrated this plugin with our Angular app but I need to do the following changes

Select option

<select ng-model="data.selectedPosition" ng-options="position.name for position in data.waterMarkImgPosition track by position.id" id="mySelect" name="mySelect" class="form-control ng-pristine ng-valid ng-not-empty ng-touched" style=""><option label="Lower Right" value="1" selected="selected">Lower Right</option><option label="Lower Left" value="2">Lower Left</option><option label="Upper Right" value="3">Upper Right</option><option label="Upper left" value="4">Upper left</option><option label="Center" value="5">Center</option></select>

1. How to set Image size for both Select the image to watermark & watermark image ?
2. How to apply position using select options rather than radio button ?
3. Any other angular plugin for the watermarking ?

Also it gives error in console at upload.js (line 176, col 7)

TypeError: document.getElementById(...) is null
document.getElementById(id).addEventListener('keyup', function () {

Tried changing upload.js from radio button to select option like below but not working

position = document.querySelector('input[type=radio]:checked').value;
position = document.querySelector('option:checked').value;

Please guide and help!
Thanks.