Creating a Negative Triangle Effect with GIMP - Requested Tutorial

Negative Triangle Effect
by pepper090889

This tutorial was requested by Datahead.

What you will need:
GIMP | Image of Choice | Triangle shape png

Tutorial:
You will begin by opening the image you would like to edit with GIMP. I will be using a pic I edited from a while back title Moon Over Autumn. Feel free to use this pic for the tutorial.

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Next, it's probably best to edit the photo to your liking before starting the negative triangle effect. Be sure to merge all layers.

First, you will need a png image of a triangle shape. It doesn't matter what color the triangle is. I will be using this one. Feel free to use the same one or find your own. This will work with any png shape or silhouette.

Save the triangle png to your computer, somewhere that is easily found.

Now, in GIMP go to File > Open as Layer and browse for and open your triangle png.

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You can resize your triangle to any size you would like by choosing the Scale Tool.

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Just click the Scale Tool button, click the triangle [you must be on the triangle layer] and close the icon next to the width and height boxes by clicking it. It should remain closed unless you want your triangle stretched.

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If you do not want your triangle in the center of your image, skip the next step.

In the Toolbox window, choose your alignment tool. Click the triangle image. In the Toolbox window at the bottom there will be twelve arrows pointing different directions. In the top set of arrows, you will want to click the two middle arrows shown below:

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This will center your triangle.

In the Layers - Brushes window, right click on the triangle layer and choose Alpha to Selection. This will outline your triangle.

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Next, in the Layers - Brushes window, choose the image you are editing. [This should be the bottom layer.]

At the top of the window, go to Colors > Invert. Then press Ctrl + A to get rid of the triangle outline. To check to see if the effect worked, hide the triangle layer. You can hide the layer by clicking the eye icon next to the triangle layer in the Layers - Brushes window.

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