How to Make Fake Rain in GIMP

This article explains how to add a fake rain effect to your digital photos using the free pixel-based image editor GIMP. Instructions apply to GIMP version 2.10 for Windows, Mac, and Linux.

How to Add Rain to a Photo in GIMP

To produce a rain effect in GIMP, you'll first create the "rain" in a separate layer, and then superimpose it over the image:

1. Go to File > Open and select the photo you want to add rain to.

2. Go to Layer > New Layer to add a new layer to build the fake rain effect upon.

3. Go to Tools > Default Colors.

4. Go to Edit > Fill with FG Color to fill the layer with solid black.

5. Go to Filters > Noise > RGB Noise.

6. Uncheck the box beside Independent RGB to link the three color sliders.

7. Adjust the Value slider to 0.70, move the Alpha slider all the way to the left, and then select OK.

   You can use different settings for this step. Generally, moving the sliders further to the right will produce the effect of heavier rain.

8. Making sure the speckled layer is selected, go to Filters > Blur > Linear Motion Blur to open the Motion Blur dialog.

9. Set the Length to 40 and the Angle to 80, then select OK.

   Higher Length values will give the sensation of harder rain, and you can adjust the Angle to give the impression of rain being driven by the wind.

10. With the rain layer selected, click on the Mode dropdown menu in the Layers palette and select Screen.

    You may notice a slight banding effect on some of the edges. To get around this, the layer can be re-sized using the Scale tool.

11. Go to Colors > Levels.

12. Select the Linear Histogram icon (the second box from the left in the top-right corner) and set the Channel to Value.

13. You will see that there is a black peak in the histogram​ and three triangular drag handles beneath. Drag the white handle across to the left until it is aligned with the right edge of the black peak, then drag the black handle to the right and select OK when you're happy with the effect.

    You can drag the white handle on the Output Levels slider a little to the left to reduce the intensity of the fake rain and soften the effect.

14. Go to Filters > Blur > Gaussian Blur and set the Horizontal and Vertical values to 1.

15. Select the Eraser from the Toolbox, then select a large soft brush and reduce the Opacity to 30-40%.

16. Brush a few areas of the fake rain layer to lend a more varied and naturalistic intensity to the effect. Add a second layer of rain using slightly different settings to add depth to the final effect.