CPanel lets you manage images files. This can be useful for changing
images dimensions.

1.Log on to Cpanel /Advanced/Image Manager

Cpanel image manager

2.The next menu will display. Click on Image Scaler.
Cpanel manage images
3. A new menu will display. Click on public_html
edit images
4. Navigate to the folder you wish to edit the image file. Click on the file icon.

edit images
5.Change the dimension (s)
6. If you want to keep the same aspect ratio, check "Keep Aspect Ratio" box
7. If you want to retain a copy of the present image file, check "Retain a copy"
8. Click on "Scale Image" to complete the process of resizing the image.

Cpanel resize images
Repeat the process for each image file you want to resize.