Sunday, 31 July 2016

GimpGuru's Tutorial For Smart Sharpen - Streamlined

There is this great tutorial by GimpGuru for sharpening pictures without amplifying the inherent noises. However, the first time when I followed his instructions, I fumbled: I didn't get my sharpened picture; I got confused instead.

But with some perseverance, I succeeded in the end.

I thought of streamlining his tutorial as I know that I will be using it often. But a day later, I found an even better tutorial/technique, '"Smart" Sharpening, Redux', also from GimpGuru. I particularly like the ability in this second technique in adjusting and observing the sharpening level, WYSIWYG-style, by merely sliding the "Opacity" slider left or right in the "Levels" dialog window.

In case if you are wondering, I fumbled on the second tutorial too the first time round - I got confused just like the first.

Tutorial - Made Simple

Below are my simplified instructions for the second method by GimpGuru. Have fun! I am using GIMP version 2.6.9, by the way.

Hint: image1, image2 and image3 are created in sequence. If you lose your bearings half way through, just refer to the Windows task bar to find your picture.

Setting Up

  1. Open your original image. Lets call this image image1.

  2. Duplicate image1 (Image -> Duplicate). Let call this newly created duplicate image image2.

  3. Go back to image1. Select Colour -> Components -> Decompose. In the "Decompose" dialog box, select HSV for "Color model". Then check "Decompose to layers". Click on the "OK" button. A new image will pop-up with imaged decomposed into "Hue", "Saturation" and "Value". Lets call this image3.

  4. Go back to image1 and open the "Layers" dialog window. Duplicate the Background layer and rename the new layer as "Sharpening". Keep the "Sharpening" layer at the very top.

  5. Go to image3. Select All (Select -> All) and Copy (Edit -> Copy)..

  6. Go back to image1. And Paste (Edit -> Paste) - image1 becomes B&W. In the "Layers" dialog window, anchor the pasted image layer into the "Sharpening" layer. Then select "Value" as the (blend) mode - image1 turns back to colour again.

    Constructing the mask

  7. Go to image2. Select Filters -> Edge Detect -> Edge. Adjust the "Amount" slider and click the "OK" button. Then convert image2 into grayscale: Image -> Mode -> Grayscale

  8. Still in image2, bring up the "Levels" dialog window (Colors -> Levels). Adjust Input levels so that areas that need sharpening are white and those that does not need sharpening is black. Click on the "OK" button.

  9. Apply Gaussian blue to image2: Filters -> Blur -> Gaussian Blur

  10. Optional: repeat step 8

  11. Select All (Select -> All), then Copy (Edit -> Copy) in image2.

  12. Go back to image1. In the "Layers" dialog, select the "Sharpening" layer. Right click and "Add Layer Mask". In the "Add Layer Mask" dialog select "White (full opacity)". Click the "OK" button.

  13. In image1, Paste (Edit -> Paste). In the "Layers" dialog window, anchor the pasted layer into the layer mask.

    Sharpening The Image

    "Layers" Dialog Window With The image (instead of the mask) Thumbnail Selected

  14. In image1, in the "Layers" dialog window select the "Sharpening" layer, and then select the thumbnail icon of the "Sharpening" image layer (see picture above circled RED) instead of the layer mask (the darker thumbnail icon on its right).

  15. Apply the "Unsharp Mask" filter to the "Sharpening" layer in image1: Filters -> Enhance -> Unsharp Mask.

  16. In the "Layers" dialog for image1, adjust the "Opacity" slider to decide on how much sharpening to use (As suggested by GimpGuru, you might want to oversharpen the image in step 15).Toggle the visibility of the "Sharpening" layer to compare the image with and without sharpening.

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