The free program GIMP (or The GIMP, as called by many sites) has established itself as a real alternative to Photoshop in the context of programs for retouching photos, showing advanced features that have nothing to envy to Adobe's paid program. If in the professional and work environment perhaps it is better to focus on a paid license of Photoshop, in the home environment we can do most of the basic photo editing operations, within everyone's reach, using exclusively GIMP. In this guide we will show you how to retouch photos using GIMP, free of charge, in the most probable scenarios, so as to learn how to use it immediately. At the end of the guide you will be struck by the potential of this open source program and you will hardly miss Photoshop (which should however be purchased in the case and it is very expensive).
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1) Where to download GIMP
The GIMP program is free and open source, i.e. free source so we can exploit it in any scenario without any licensing problem. GIMP is available for Windows, Mac and Linux from here -> Download GIMP .
From the site, simply click on the Download button to open the dedicated page based on the operating system we are using.
Once downloaded on our PC or Mac just start the downloaded file with a double click and confirm all the installer screens to get the program. On Linux GIMP may already be included in the starting software, otherwise we can download it by looking for it in the Software Center of our distribution or, if we have a Debian-based operating system, run the following command from the terminal:
sudo apt install gimp
When prompted, enter the administrator password and confirm to install the program correctly.
2) How to open and save images
One of the first things we need to learn to use on a new photo retouching program are the keys to open new images and the keys to save new images (after modifying them). To open new images, simply launch the program and click on the top menu on the File -> Open menu.
We select in the file manager that one or more images will open to be opened inside GIMP; if we want to create an empty image (a sort of "sheet" that we can fill in) just click on the File menu -> New and choose the proportions of the new empty image (we recommend clicking at the top on Templates and selecting A4 sheets, choosing then whether to position it horizontally or vertically). All image files will open as tabs inside the program, at the top of the program.
After making all the necessary changes, we can save the modified image by clicking on File -> Export (if we want to overwrite the original file) or File -> Export as (to change the name and extension).
The file manager will open again, where we can choose the location where to save the file and its extension.
3) How to move a selection to another image
We have images to put together in one (for example, the back of the identity card or the tax code) ">
Once this tool is selected, we move the mouse to the corner of the image (or part of the image) and, holding down the left mouse button, we draw a rectangle that also includes the image selection. If we have to move the whole image, we can also directly press CTRL + A on the keyboard, after activating Rectangular selection . As soon as we see the selection appear with flashing dashes, we press CTRL + C on the keyboard, then we go to the empty image or the image in which to paste the selection, then we press CTRL + V to paste.
If we have done everything correctly we will see the copied image appear in the other image; if the dimensions are "unpacked" or the rotation is not correct, we recommend that you read the chapter How to rotate and resize an image or a selection later on. If the contours of the object to be selected are not so "sharp" (a person, a part of the landscape etc.), instead of the Rectangular Selection we recommend using the Fuzzy Selection, Smart Scissors or Paths tools.
4) How to remove red eyes
If we decide to edit photographs taken with an SLR or a digital camera, one of the first features that we will use is the system to remove red eyes. On GIMP removing red eyes is really very simple: we launch the program, then we open the offending photo as seen above.
Once the photo is open, click on the Filters menu and open the item Improvement -> Red-eye removal .
A small filter menu will appear, which for now we can ignore; let's go back to GIMP, adjust the zoom down so as to put the eyes in the foreground to be corrected.
Now that the eyes and red pupils are in the foreground, we use the Elliptical Selection tool present in the toolbar to draw an ellipse around the eye; now all we have to do is open the filter window seen a little while ago and click OK . Automatically the red eye effect will be corrected, with a color gradient similar to the black of the pupil (which without zooming will not be noticed at all). We repeat the step for the other eye and save the corrected image as seen previously.
5) How to adjust the basic parameters (brightness, contrast, saturation)
We want to correct photos with completely unbalanced colors and brightness ">
We recommend starting with adjusting the Color Balance, then moving on to Saturation and Brightness and Contrast .
Each item will open a small configuration window, where we can apply various setting levels and observe, in real time, the effect it has on the photograph.
To better notice the differences between "before" and "after", we can also activate the Split view item present in each adjustment window of the basic parameters.
6) How to rotate and resize an image or selection
We have moved an image or selection to another image but the aspect ratio is completely wrong ">
Selecting these tools after copying the selection, we will see a deformable field appear around it, so that we can rotate or change the aspect ratio of the image. Using the Rotate tool, just rotate the cursor in the center to make the rotation, while using the Scale tool, simply click on one of the squares on the edges of the image to change its size and adapt it.
7) How to correct a blurred or blurred image
When we take photographs, it can happen that we have blurred or blurry photos. Assuming that the best results are obtained only by improving our shooting skills, to try to solve a blurred or blurred image problem just click on Filters -> Improvement and use the Antialias and Unsharp Mask plugins.
By increasing the level of anti-aliasing or by applying a very accentuated artificial contrast, in the vast majority of cases we will be able to soften the effects of a blurred or blurred photo. Obviously we cannot do miracles with each photo, better therefore to make good shots rather than act later.
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