Another interesting and useful technique to use with selections is the selection inverse feature. If you make a selection from an image, and apply the inverse feature, all regions of the image that are not in the selection will become the selection (that is, you have inverted the selection).

 

 

 

 

Here we have an image with a basic rectangular selection. If you right click on the image, and choose Select Inverse from the menu options, you will see another animated dashed border surrounding the outer edges of the image. This second border indicates that the region of the image outside the inner rectangle is now the selection. For an example of this, please examine the following image.

 

 

The second border is now visible after clicking the select inverse option. (Shading has been added to indicate the new inverted selection.) The new selection, or inverse, is the area outside of the original rectangle. You can also press Shift + Ctrl + I as a keyboard shortcut to select the inverse.

 

Yet another interesting effect that you can use with your selections is skewing. Skewing could be described as a uniform transformation of the alignment of your selection, as a means of altering the geometry of the selection based on a given direction. To understand this better, take a look at the following example.

 

 

Here we have a greyscale image of a door, where the door itself has been selected using the rectangular marquee tool.

 

The first step in skewing this selection is to right click on the image to display the pop up menu options. From the list of options, click the Free Transform option (normally we would choose Transform Selection). By using free transform, the image pixels will be skewed along with the selection to better illustrate the effect. If you use transform selection only the dashed selection border will be skewed (not the image). When you click the free transform option, a perimeter box with move handles will be formed around the selection. Now, right click the image again and a menu of transformation options will appear. If you select the Skew option from this menu, and drag the top   move handle on the transform box to the left, you will see your selection as it is skewed in the direction of your mouse pointer.

 

Here is the selection after it has been skewed.

 

As before, you must click the checkmark on the options bar to commit to the transformation.

 

Another way to manipulate your selection is to apply feathering. Feathering is a way of softening and blending the edges of a selection or image. Feathering can be used to build montages and create interesting effects with your images.

 

To feather a selection, first choose a selection tool and make your selection. The next step is to right click on the image, and choose the Feather option from the pop up menu. When you do this, the following dialog box will appear.

 

 

Enter a value in the Feather Radius field to control the how much of the selection edge will be seen after the softening effect. The larger the number, the more gradual the softening (you will see more of the image around the edge). For this example, a feather radius of 25 was used. After you enter a value, click the OK button to feather your selection.

 

To see the feathering effect, right click on the image again, and choose select inverse from the menu. When you see the selection border around the outer edge of the image, indicating that the selection has been inverted, press the delete button on your keyboard to delete the selection (the inverse of your original selection). Performing this action will show the dramatic feathering effect.

 

Here is the original selection, with the results of the feathering action clearly visible.

 

The inverse of the selection was removed as described above so the feathering effect could be easily shown.