With Lucidchart, you can crop an image in seconds.
Select a user uploaded image and...
Right-click > Edit Mask
From the Menu bar, Edit > Edit Mask, OR
From Graphic panel on the right dock click Edit Mask.
Four white sqaures will appear around the outside to re-size the image, and four black marks on the inside to crop. Drag the crop marks to adjust the portion and size of the user image you would like visible.
Once the crop marks have been adjusted, press Enter to save the crop, or press Escape to exit crop-editing mode without saving any changes.
Changing the size or orientation of the image does not affect the crop. The crop is also non-destructive, so you can restore or adjust the image cropping at any time.