Produce Fake Rain in GIMP

Tutorial to Add Fake Rain to a Photo in GIMP

This tutorial shows you a simple technique for adding a fake rain effect to your photos using the free pixel-based image editor GIMP. Even relative newcomers will find that they are able to produce exciting results following these steps.

The digital photo used in this example is 1000 pixels wide. If you use an image that is significantly different in size, you may need to adjust some of the values you use in some settings to make your fake rain look more suitable. Do remember that real rain can look very different depending on the conditions and that by experimenting you will be able to produce different effects.

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Select a Suitable Digital Photo

You can add a fake rain effect to any digital photo that you have, but to make it more convincing, it is best to choose an image that looks like it could have been raining. I've selected an evening shot across an olive grove when there were very dark and foreboding clouds allowing shafts of sunlight to shine through.

To open your picture, go to File > Open and navigate to your photo and click the Open button.

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Add a New Layer

The first step is to add a new layer that we will build our fake rain effect upon.

Go to Layer > New Layer to add a blank layer. Before filling the layer, go to Tools > Default Colors and now go to Edit > Fill with FG Color to fill the layer with solid black.

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Add the Seeds of Rain

The basis of the rain is produced using a noise Filter.

Go to Filters > Noise > RGB Noise and uncheck Independent RGB so that the three color sliders are linked. You can now click on any one of the Red, Green or Blue sliders and drag it to the right so that the values of all the colors show as about 0.70. The Alpha slider should be positioned fully to the left. When you've selected your setting, click OK.​

Note: You can use different settings for this step – generally moving the sliders further to the right will produce the effect of heavier rain.

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Apply Motion Blur

The next step will convert the speckled black and white layer into something that starts to bear some resemblance to falling fake rain.

Ensuring that the speckled layer is selected, go to Filters > Blur > Motion Blur to open the Motion Blur dialog. Ensure that the Blur Type is set to Linear and then you can adjust the Length and Angle parameters. I set the Length to forty and the Angle to eighty, but you should feel free to experiment with these settings to produce the result that you think best suits your photo. Higher Length values will tend to give the sensation of harder rain and you can adjust the Angle to give the impression of rain being driven by the wind. Click OK when you're happy.

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Resize the Layer

If you look at your image now, you may notice a slight banding effect on some of the edges. If you click the previous thumbnail, you will probably notice that the bottom edge looks a little ragged. To get around this, the layer can be re-sized using the Scale Tool.

Select the Scale Tool from the Toolbox and then click on the image, which opens the Scale dialog and adds eight grab handles around the image. Click on one corner handle and click and drag it a little so that it overlaps the edge of the image. Then do the same to the diagonally opposing corner and click the Scale button when you're done.

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Change the Layer Mode

At this point, you can probably see a hint of rain about the layer, but the next few steps will make the effect of fake rain come alive.

With the rain layer selected, click on the Mode dropdown menu in the Layers palette and change the Mode to Screen. It's possible that this effect may already be pretty much what you were hoping for, though I would at least suggest you look at using the Eraser tool as described in the step before the Conclusion. However, if you want a more irregular effect, continue to the next step.

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Adjust the Levels

Go to Colors > Levels and check that the Linear Histogram button is set and that the Channel dropdown is set to Value.

In the Input Levels section, you will see that there is a black peak in the ​histogram and three triangular drag handles beneath. The first step is to drag the white handle across to the left until it is aligned with the right-hand edge of the black peak. Now drag the black handle to the right and check the effect on the image as you're doing this (ensure that the Preview checkbox is activated).

When you're happy with the effect, you can drag the white handle on the Output Levels slider a little to the left. This reduces the intensity of the fake rain and softens the effect. Click OK when you're happy.

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Blur the Fake Rain

This step is designed to make the effect a little more naturalistic by softening the fake rain.

Firstly go to Filters > Blur > Gaussian Blur and you can experiment with the Horizontal and Vertical values, but I set mine both to two.

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Use the Eraser to Soften the Effect

At this point the fake rain layer appears quite uniform, so we can use the Eraser Tool to make the layer less uniform and soften the effect.

Select the Eraser Tool from the Toolbox and in the Tool Options that appears below the Toolbox, select a large soft brush and reduce the Opacity to 30%-40%. You want quite a large brush and you can use the Scale slider to increase the brush size. With the Eraser Tool set up, you can just brush a few areas of the fake rain layer to lend a more varied and naturalistic intensity to the effect.

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This is quite a simple technique with steps that should allow even a newcomer to GIMP to produce striking results. If you give this a go, don't be afraid to experiment with the different settings at each step to see the different types of fake rain effects that you can produce.​

Note: In this final screen grab, I've added a second layer of rain using slightly different settings throughout (the Angle setting in the Motion Blur step was kept the same) and adjusted the Opacity of the layer in the Layers palette a little to add a little more depth to the final fake rain effect.

Interested in creating fake snow? See this tutorial.