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GIMP TutorialsIncrease Contrast of an Image using Luminosity Mask in GIMP (Showcase | Slideshow)

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Increase Contrast of an Image using Luminosity Mask in GIMP

Post#1 by trandoductin » 07 Oct 2016, 20:10

I highly recommend you read over this tutorial --> Getting around in GIMP Luminosity Masks by PatDavid.

After following the above tutorial, I wrote a simple script that creates
all 9 luminosity masks which can downloaded from Luminosity Masks script on

0. You just have to download the Luminosity_masks.scm file, and put it in your GIMP's /scripts/ folder (like for example on my windows machine, i put it under C:\Users\Tin Tran\.gimp-2.8\scripts)
We'll be using this script here to play with luminosity mask.
What I usually like to do is apply lots of contrast to the M layer, it makes the image pop. So here's what i do.

1. Open up an image in GIMP (menu "File", then "Open", then browse to your image file and click "Open"). Here we're using an image from Halong bay, Vietnam image as an example.
playing_with_luminosity_mask_01_open_image.png # (806.09 KiB) Viewed 1133 times (Watermarked | Thumbnail)
2. Because we're downloaded the file in Step 0. We have this menu "Script-Fu", then "Create New", then "Luminosity Masks" available. So run that.
playing_with_luminosity_mask_02_Script_Fu_Create_New_Luminosity_Masks.png # (26.01 KiB) Viewed 1133 times (Watermarked | Thumbnail)
3. The script will create 9 new layers on top of your original layer (defaulted to invisible without the eye icon turned on). The layers are named L, LL, LLL, D, DD, DDD, M, MM, MMM. L stands for Light, D stands for Dark, and M stands for Mid. For this tutorial, we're interested in the M (Midtone layer).
playing_with_luminosity_mask_03_9_layers_will_be_created.png # (383.32 KiB) Viewed 1133 times (Watermarked | Thumbnail)
4. Click on the M Layer to make it active (in the Layers window), then click on the left of layer to toggle to eye icon to show which will make that layer visible.
playing_with_luminosity_mask_04_click_on_M_layer_then_click_to_toggle_the_eye_to_show.png # (384.31 KiB) Viewed 1133 times (Watermarked | Thumbnail)
5. Now go to menu "Colors" then "Brightness-Contrast...". An "Adjust Brightness and Contrast" will pop up. Play with contrast by dragging it and dragging left/right. You can toggle the "Preview" to see the difference of before and after. Once you're happy with the increased in contrast (you can go pretty high without damaging the image completely), click "OK" button. Here, as an example, I have increased contrast to 60.
playing_with_luminosity_mask_05_Adjust_Brightness_and_Contrast_window_play_with_contrast_toggle_Preview.png # (60.8 KiB) Viewed 1133 times (Watermarked | Thumbnail)
6. And here's the result.
playing_with_luminosity_mask_06_contrast_at_60_on_M_layer_result.png # (860.18 KiB) Viewed 1133 times (Watermarked | Thumbnail)
7. Now you can go to menu "File", then "Save As..." to save your work as an .xcf file to work with later. Or you can go to menu "File", then "Export As..." (on Windows) to export your result as an image file (a .png file or a .jpg file).

And here's a comparison of before and after applying high contrast to the M Layer.
playing_with_luminosity_mask_07_before_after_comparison.png # (258.52 KiB) Viewed 1133 times (Watermarked | Thumbnail)
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Post#2 by SukieKat » 03 Jul 2017, 22:02

I highly recommend you read over this tutorial --> Getting around in GIMP Luminosity Masks by PatDavid.
Thank you so much for your recommendation. I found the tutorial highly helpful and instructive.

PS: I also completed your tutorial and installed your script. Thanks again.
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