How To Use the GIMP Select by Color Tool for Selections
Knowing which selection option to use in GIMP is half the battle when editing your images. The other half is knowing how to use it. When it comes to the Select by Color tool, it does what its name implies; makes a selection based on color!
Today, you’ll discover everything you need to know about the Select by Color tool and how to use it. If you’re ready… let’s do it!
Table of Contents
What is the Select by Color Tool,
The Select by Color tool option allows you to make a selection of your image based on a range of hues. This is useful for several editing scenarios; selecting a sky for replacement, changing a specific color to another, targeting a color to reduce saturation, and much more.
In a way, Select by Color is similar to the Fuzzy Select. Both make a selection based on color. However, there is a distinct difference…
Select by Color Tool Options
Both Fuzzy and Select by Color have almost identical choices for tweaking the settings. It has five main sections for fine-tuning what’s selected. Let’s review each section, so you know how each affects what’s chosen.
First, access the Select by Color tool with the keyboard shortcut Shift + O. If the Options panel is not already visible, go to Windows > Dockable Dialogs > Tool Options.
In this section, you’ll find four icons with the following properties…
These settings will refine the quality of the edges of what’s chosen.
This setting determines how aggressive the color range is when determining which hues to choose. The higher the Threshold, the more pixel values will be added or subtracted from what’s chosen.
Use this setting if you’d like to target a specific hue channel: Composite (RGB), Red, Green, Blue, Alpha, HSV Hue, HSV Saturation, HSV Value, LCh Lightness, LCh Chroma, and LCh Hue.
If you’re having a hard time seeing the marching ants (what’s selected), you can use this setting to include a mask. To see the mask, hold down your left mouse button in the same area where you clicked. This will reveal a magenta mask (overlay) on your photo indicating what’s been selected.
Tips For Using the Select by Color Tool
As with any selection means in GIMP, you’ll need to tweak your settings to get precisely the hues you need to be chosen. In fact, you may need another tool to fine-tune for precise selections. Let’s review a couple of images to see how to use Select by Color.
A Simple Photo
The key to using Select by Color is the Threshold setting. It’s possible to leave the settings at their default and only adjust the Threshold as needed. Although, you’ll need to add or subtract to fine-tune what’s chosen.
For the first image, I started the Threshold at 50, and GIMP did a pretty good job of selecting both orange slices. To see what would happen, I doubled the Threshold to 100, and as you can see, it began selecting the table too.
After lowering the Threshold back to 50, I used the “Add” mode to refine the selection. It took several clicks on each slice to get 95% selected.
The last click resulted in the surface being added too. This required undoing that step and then using the Quick Mask mode to finalize it (third image).
There’s a vast range of “green” pixel values in the mountains for our next image. At first, you might think a higher Threshold will get the job done. Let’s review the following two photos…
This photo shows what’s chosen at a Threshold of 25…
After increasing the amount to 50, more of the “green” is chosen. So too are the mountains in the background. You’ll have to decide what parts of an image should be included and what shouldn’t.
One more thing about this image… after multiple clicks, I realized that the Select by Color wasn’t the best solution for getting what I needed. A quicker and simpler method would have been the Quick Mask mode.
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