This GIMP (GNU) tutorial demonstrates how to fill an iris with rainbow colours. To work along, you are welcome to download the Start Image I am working with Here. Unzip the file and open the image onto GIMP’s workspace.
You can quickly Undo a step at any time by pressing Ctrl then Z. Alternatively, click a previous Undo History snapshot - Windows then Dockable Dialogues then click Undo History. In addition, to Zoom in (or Zoom out) of your image; from the top menu choose View then select a Zoom Tool from the subsequent drop-down list.
Free Select Tool
Understand Blend Modes
Launch GIMP & Organise Its Workspace & Palettes
Open your choice of Start Image onto GIMP’s workspace - File then Open - Ctrl then O.
Ensure the Layers and the Undo History Palettes are visible, and then drag them into position over your workspace - (Windows then Dockable Dialogues - then click Layers and Undo History).
Now, create a New Transparent Layer by clicking the Layer Palette’s Create a new layer tab, as illustrated below-left. Then click OK to the subsequent New Layer dialogue box, as illustrated below-right.
You’ll be applying your rainbow blend onto this New Transparent Layer.
For accuracy, Zoom into the eye: - top menu, then View then Zoom. (I zoomed in three times).
Shift+Plus Key And Minus Key Tip
To quickly zoom in or out of an image - tap your Keyboard’s Shift+Plus Key or the Minus Key, respectively.
If necessary, you can navigate your image using the Right-side and Lower Scroll Bars.
Now, from the left-side Toolbox, activate the Free Select Tool.
And enter the following Add to the current selection and Feather 20 Radius settings into the left-side Tool Options Box.
Remember, the Feather setting is perfect for my Start Image. However, the Feather is entirely dependent on your Image’s Resolution - (Size). Therefore, when working with your own start image, it’s important to find the right Feather setting that suits your image requirements.
Tip - Retracing Your Steps
Whilst you are applying the Lasso Line; - and before the Selection Marquee has been
applied, to go back one step - press your Keyboard’s Backspace Key. Press the Backspace Key for however many steps you want to go back - (this is for Window PC users, I am unfamiliar with Mac’s). Tapping the Escape Key completely removes the Lasso Line/Selection Marquee.
Cancel The Selection Marquee Tip
To cancel the Selection Marquee whilst applying it: press your Keyboard’s ESC Key.
Working on the New Layer, you are looking to click-and-stretch a “Lasso Line” around the iris - with the aim of isolating it with a Selection Marquee. Therefore, click and stretch a Lasso Line around the iris in a complete circuit. Then pass your cursor over the exact point where you began, then left-click. This converts the Lasso Line into a Selection Marquee.
Go ahead and isolate the second iris if your start image displays both eyes.
After you have have isolated the iris, or irises, with a Selection Marquee, you are ready for the next step.
From the Layers Palette, change the Transparent Layer’s Blend Mode from Normal to Overlay - as illustrated below. (Layers, Blend Modes).
Now, from the left-side Toolbox, activate the Blend Tool.
And from the Blend Tool’s Tool Options box, set a Gradient Blend of your choice - as illustrated below.
I am selecting a bright rainbow, however, by all means, select a blend you are happier with.
I have selected the Spiral CW Shape, however, for personal results, it’s important to experiment with different Gradient Shapes.
Now, (still working on the New Transparent Layer). Left-click and stretch a “Gradient Line” over the iris - as illustrated below.
As soon as you release the mouse button, a gradient will be applied inside the selected iris, or irises, as illustrated below.
To deepen the effect, repeat the gradient application. However, you may wish to lower the second Gradient’s Opacity if you feel two 100% applications results in an over saturated blend.
From the top menu, choose Select and then choose None.
Prior to Flattening the Layers, (and still working on the New Transparent Layer), from the left-side Toolbox, activate the Eraser Tool, and very carefully remove any colour that may have transcended into the white eyeball (sclera). Eraser Tool Tutorial.
To finish, from the top menu, choose Image and then choose Flatten Image.
Your image will benefit from a Sharpening Filter: Filters then Enhance - (I have applied the Unsharp Mask). Sharpen Images Tutorial.
Congratulations, your Rainbow Eye Blend is complete and it is ready to save.
Now you are more familiar with this technique, you can have lots of fun resurfacing irises.
Wendi E. M. Scarth. Top of Page.