This tutorial shows you how to use the Cell Transform tool in GIMP 2.8, which provides a powerful and versatile way to transform photos and areas in photos. This won’t be immediately helpful to all GIMP users, although it can be a useful way for photographers to reduce the effects of perspective distortion. In this tutorial, we’ll use a perspective-distorted image as a base to show you how to use the new tool.
Perspective distortion occurs when the camera lens has to be tilted to capture the entire subject in frame, such as when shooting a tall building. For this tutorial, we deliberately caused perspective distortion by going downstairs and photographing the door to the old barn. If you look at the image, you will see that the top of the door appears narrower than the bottom, and this is the distortion we are going to correct. Although it is a bit of a wobbly shed, rest assured that the door is in fact rectangular.
- Using the Cage Transform Tool in GIMP
- Apply cell to image
- Rotate the cell to transform the image
Using the Cage Transform Tool in GIMP
If you have a photo of a tall building or something that suffers from perspective distortion, you can use that image to walk up the stairs. If not, you can follow the photo shown here.
Apply cell to image
The first step is to open the image and then add a cage around the area you want to transform.
Go to File > Open and navigate to the file you will be working with, click on it to select it and click the button Open †
Click now Cell Transformation Tool on the toolbar and you can use the pointer to place anchor points around the area you want to transform. You just need to left click to place the anchor. You can place as many anchor points as needed and finally close the cage by clicking on the start anchor point. At this point, GIMP does some calculations in preparation for transforming the image.
To change the anchor position, click Create or customize a cage below Toolbar and then use the pointer to drag the anchors to new positions. , you will have to choose distort cell to re-distort the image before transforming the image.
The more accurately you place these anchors, the better the end result will be, but keep in mind that the result will rarely be perfect. The converted image may suffer from alt distortion, where parts of the image overlap other parts of the image in strange ways.
In the next step we will use a cell to apply the transformation.
Rotate the cell to transform the image
Now that the cage has been applied to part of the image, it can now be used to transform the image.
Click on the anchor you want to move and GIMP will do some more calculations. If you want to move more than one anchor at a time, you can hold down the Shift key and click other anchors to select them.
You then simply click and drag the active anchor, or one of the active anchors if you have multiple anchors selected, until they are in place. When you release the anchor, GIMP makes adjustments to the image. In this case, we first adjusted the top left anchor and after we were happy with the effect in the image, we adjusted the top right anchor.
When you are satisfied with the result, just press the button yield on the keyboard to perform the transformation.
Results are rarely perfect, and to get the most out of using the Cage Transform Tool, you’ll also want to familiarize yourself with the Clone Stamp and Healing tools.