GIMP Edit a digital photo to remove a curved picture
GIMP is suitable for a wide range of digital photo editing applications, from simple to quite advanced digital photo editing. A common problem that often needs to be corrected in digital photos is straightening a crooked or distorted horizon. This can be achieved very easily with the help of GIMP, as shown in this tutorial. This tutorial uses a slightly different technique than the earlier tutorial for straightening Sue ‘s GIMP ; here you will learn to use the corrective option of the GIMP rotation tool . If you are a Paint.NET user , I have already covered this digital photo editing technique in this Straighten the Horizon with the Paint.NET tutorial .
For the purpose of this lesson, I deliberately made the horizon of a digital photo crooked, so don’t worry that I was standing at a level crossing while she was screaming.
01 of 07
Open your digital camera
You will obviously need a digital picture with a meandering horizon for this lesson. To open the photo in GIMP, go to File > Open and go to the photo and click the Open button .
02 of 07
Select the Rotate Tool
You can now set the Rotate Tool in preparation for horizon adjustment.
Click the tool for rotation in the box with tools and you’ll see options to rotate palette in the box with tools . Check that the transformation is set to layer and change the direction of correction (backward) . I would recommend using the Cubic setting for interpolation, as this creates good image quality. I prefer to change the optionClipping to ” Crop” to get a result, as this will result in an image that has vertical and horizontal edges and will make the resulting image as large as possible. Finally, set Preview to Grid , set the next drop-down window to Number of line grid, and move the next slider to 30.
03 of 07
Activate the rotation tool
The previous step can set the tool to spin completely different from the way you normally use, but these settings are ideal for this technique to edit digital photos to get up horizon.
When you click on the image, you will see the Rotate dialog box and a grid superimposed on the image. The Rotate dialog box contains a slider that allows you to rotate the net, but we will rotate the net by clicking directly on it and dragging it with the mouse, as this is more intuitive.
04 of 07
Rotate the grille
Now we want to rotate the grid so that the horizontal lines align with the horizon.
Click on the image and drag the mouse and you will see that the digital photo remains fixed, but the network rotates. The goal is to bring the horizontal lines to the horizon and when you achieve this, click on the ” Rotate ” button .
05 of 07
Check the result
You should now have a digital photo that is smaller than before in a transparent frame.
If you are not satisfied that the horizon is straight, go to Edit > Undo Rotate and then try using the Rotate Tool again. You can click on the ruler at the top of the document window and move the guide if you want to take a closer look at the horizontal lines in your photo, but usually an eye check is sufficient.
06 of 07
Crop the digital photo
The last step in this digital photo editing tip is to remove the transparent area around the photo.
Go to Image > Autocrop Image and the transparent frame is removed automatically. If you added a guide in the previous step, just go to Image > Guides > Remove all Guides to remove it.
07 of 07
Thanks to the option correction tool for rotation of GIMP, this common technique for editing digital photos straightening the horizon is very clear. The same technique can be applied to digital photos that have strong vertical lines that are curved, like buildings.