Some fellow SUDSOLers have shared these links with me and I thought you’d love them, especially if you don’t already have an image editing program like Photoshop or Photoshop Elements.
I have not used these personally but here great things about them!
This online resource lets you resize an image, crop an image or do some advanced image editing like sharpening, sketching, or setting the pixels to specific dimensions.
This online resource is a little more advanced. It allows you to make changes to a bunch of images at a time in "batch" mode; supports JPF, GIF, PNG, TIFF and other image file formats; resize, crop, rotate images as well as add text and watermarks and much more!
Hope this helps!