Sharpen Image Edges in GIMP (High Pass Filter)

In this tutorial, I will show you how to sharpen image edges in GIMP 2.10.14 using the High pass filter.

Sharpening works by increasing contrast at edges in the image. Remember to reduce image noise before sharpening so that you don’t intensify the noise. The best way to sharpen an image is by using separate layers. Make separate layers for noise reduction and high pass filter.

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Jump to:

• Step 1: Open Image
• Step 2: Zoom Image up to 100%
• Step 3: Duplicate Layer
• Step 4: Apply Noise Reduction
• Step 5: Create a New Layer Group
• Step 6: Duplicate the "Noise Reduced" layer two times
• Step 7: Move Both Duplicate Layers to the Sharpen Group Layer
• Step 8: Apply The High Pass Filter
• Step 9: Change its Blend Mode to Hardlight or Softlight
• Step 10: Save Document

Step 1: Open Image

Use File>Open or press Ctrl+O.

Navigate through your folders in the Places panel and the Name panel until your images' name appears in the Name panel. Click the image you want to open then click Open.

For this GIMP tutorial, I'll use this image, 1282309, that I downloaded from Pixabay.

Step 2: Zoom Image up to 100%

Zoom Image up to 100% to get an accurate view of the sharpening. Use View> Zoom>1:1 (100%). This option maximizes the image.

Zoom image to get an accurate view.

Step 3: Duplicate Layer

Preserve your original image by duplicating the image layer. Go to Layer>Duplicate Layer or else just press Shift+Ctrl+D.

This creates a new perfect copy of the currently active layer just above. We will apply the Noise Reduction filter to this duplicate layer. You can name this duplicate layer with “Noise Reduction”.

Step 4: Apply Noise Reduction

Activate the duplicate layer by clicking on it then use Filters>Enhance>Noise Reduction.

In the Noise Reduction pop-up window, enter a value for the Strength through the up and down arrows.

If you're not happy with the result, you can quickly undo a step at any time by going to Edit>Undo or else just pressing Ctrl+Z.

Experiment with different values and discover values that work best for your image. Once you are satisfied with the result, click "OK" to apply it to the image.

Step 5: Create a New Layer Group

Use Layer>New Layer Group to create a new group layer. 

You can name it "Sharpen".

Step 6: Duplicate the "Noise Reduced" layer two times

Use Layer>Duplicate Layer. The top duplicate layer is for the high pass filter.

Rename the top duplicate layer with a new name like “High Pass Filter”. The top duplicate layer is for the high pass filter.

Step 7: Move Both Duplicate Layers to the Sharpen Group Layer

Drag to move both duplicate layers to the Sharpen group layer. Make sure the High Pass filter layer is on top position.

Step 8: Apply The High Pass Filter

Make sure the High Pass Filter layer is selected in the Layers dialog. Use Filter>Enhance>High Pass Filter.

Experiment with different Std.Dev and Contrast value. We want to increase contrast only along the edges.

After applying High Pass.

Step 9: Change its Blend Mode to Hardlight or Softlight

Change the high pass filter layer mode to Hardlight or Softlight.

Step 10: Save Document

Use File>Save in the top menu or Ctrl+S. In the “Save Image” dialog, type your document's name in the “Name” box and save it.

You should save it using the extension “.xcf”. XCF is GIMP's native format, and is useful because it stores everything about your image and will allow you to later edit your image in GIMP, in case you notice a problem.

Once you have finished, you will probably also want to export the image in a more widely used format, such as JPEG, PNG, TIFF, etc.

Here is the result:

More on GIMP Tutorials:

• How To Sharpen Image in GIMP (Unsharp Mask)
• How to remove Background in GIMP using Paths Tool
• How to Add graphic watermark to photo in GIMP
• Selective coloring in GIMP

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