I am try to add cropper.js in semantic modal. i am doing following step.
1) I have button on page called [Choose image]
2) If i am click on choose image one modal is open name is [thumbs]. thumbs modal have 2 button [choose from local pc] and [choose media].
3) If i am click on choose from local pc file dialog is open and image picker is working and cropper.js is assign to selected image perfect
4) If i am click on choose media button they open [media] modal and i have lots of images there and i have one button on each image if i am click on image path is pass to previous modal called thumbs and cropper tool is assigned but size is smaller as given size, if i am open inspect element of chrome cropper size is perfect.
You will better idea using following images.
If see last 2 images you can difference in image.
I am using https://fengyuanchen.github.io/cropperjs/ for cropper function.
Thanks