GIMP - the best free image editor
GIMP (the GNU Image Manipulation Program) is a free image-editing tool that's powerful enough to rival paid-for software like Photoshop - and it's surprisingly easy to use. Its array of picture-perfecting tools make it easy to boost colors, correct tones and erase blemishes before sharing them on Facebook.
supports all the most popular image formats, including TIFF, JPG, GIF, PNG and PSD, so you should be able to open up your photos and start editing them immediately. If your snaps are in a format not supported by default, GIMP's users have created a set of free plugins to help. UFRaw is particularly useful if your camera shoots in RAW format.
Make flat photos shine
It only takes a few small changes to turn ordinary holiday snaps into something special. One of the most useful tools for this is Curves, (select 'Colors > Color Curves'), which is a great way to boost flat-looking images.
The left-hand side of the Curves window controls the shadow tones in your images and the right-hand side controls the highlights. Tweaking the diagonal line into a gentle 'S' shape will increase the contrast in your image - as subtly or dramatically as you like.
Remove color casts
Another extremely handy tool for quick photo-editing is White Balance. Most modern compact cameras do a good job of adjusting for different lighting conditions, but the same can't be said for phone cameras. Warm indoor lighting in restaurants and bars often results in pictures with an odd-looking yellow cast. There are a couple of ways to correct this.
Select 'Colours > Auto > White Balance' and GIMP will attempt to gauge the temperature of the colours and compensate accordingly. This usually works well, but if you'd rather correct tones manually select 'Colours > Levels' and adjust the levels of red, green and blue yourself.
Clone out flaws
If something small is spoiling an otherwise brilliant shot - a lamp post in the background for example, or a speck of dirt on your camera lens - the Stamp (or Clone) tool is a convenient way to paint it out. Move the tool over a part of the image, hold [Ctrl] and click to take a sample from an area, then click and drag the brush over the unwanted object to cover it up. This also works for small blemishes.
GIMP's automatic options also make it easy to correct red-eye, crop your pictures to improve composition, resize them if they're too large to upload to your preferred social media platform, and export them in a more convenient format.
Once your holiday pictures look perfect, select 'File > Export' and choose a name, format and location for the edited image. Your original photo won't be altered or overwritten unless you explicitly tell GIMP to do so.
Then just upload your polished snaps to Facebook and become the envy of your friends and family. Easy!