First, you will need some type of image editing software that will let you crop an image. If you don't already have software that was included with your camera or scanner, then you can download shareware image editing software that can do the trick. You don't have to buy an expensive image editing software suite to crop and resize an image.

For this tutorial I will be using adobe photoshop to crop my image. The technical procedure will be different for each software product, so I will focus on concept only. Starting with this painting of an alien girl, I want to create a thumbnail that will be interesting. Simply reducing the size of the image to 80 pixels is not in my best interest here. Although some images are perfectly suited for a simple reduction in size, in my opinion, this one isn’t.

So I select an area to crop that will be an interesting image by itself, and create a curiosity with the browser so that they will click on the thumbnail to see the fullsize image. In adobe photoshop, I hold the shift button down while selecting the crop area so that it remains perfectly square. The size of the crop is not important right now, just the composition.

Once I have my cropped area, in this example it is 110x110 pixels, I resize the image to 80x80 and save it with a new filename such as tn_image.jpg. This distinguishes my thumbnail from my fullsize which is image.jpg. Then I am ready to upload the thumbnail into the thumbnail box, and the fullsize image into the image box on the upload page.