Sizing and Cropping Images in Gimp
If you do not have photoshop to re-size your images, try using Gimp.
Gimp is a free open-source image editor.
To re-size an image:
Download Gimp and install it.
File >> Open
Navigate to the image you want to re-size
and click Open button.
Image >> Scale image
set both x and y resolution to 72
and then set longest side of the image to the desired size longest measurements
click scale button
Now to crop the image so it is the correct proportion :
From the rulers, drag down a guide to the precise measurement of the second shorter side. Note: there is an exact location coordinate at the bottom of the window.
Select the crop icon in your tool box
Click and drag box to the correct proportion and
let go.
and click on the image to crop.
Check back at
Image >> Scale image window
to make sure you have the correct proportions and resolution.
Save as a new document.