Episode 164: High Pass Sharpening

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Sharpening is a part of nearly every image processing. Selective sharpening allows to sharpen the important structures without to “enhance” the noise in the image. Already in Episode 6 I have shown a way to do this. And here is another way, High Pass Sharpening. It is often used in Photoshop tutorials and has no standard entry in the GIMP menus.

One step involves blurring – and this leads to a lot of different possibilities to change the effect. I explore asymmetric sharpening by blurring only into one direction.

Of course there are plugins available at the GIMP plugin registry.

A description of several sharpening methods is in our Wiki, I’ll add the high pass method today.

I got the recipe for this from a (very good) German book by Jürgen Wolf.

The TOC

01:48 Good German book: Jürgen Wolf, GIMP 2.6
02:00 GIMP 2.8 release late in 2011!
02:20 Preparing the image
02:40 Rotate
03:30 Crop
04:10 Contrast, black point and white point adjustment with the curves tool
05:30 The recipe for Highpass Sharpening
05:40 Duplicate the layer twice
05:50 Invert the colours
06:00 Set layer mode to Grain Merge
06:10 Blurring
07:00 Merge the top layer down and set the layer mode to Overlay
07:50 Adjusting the effect with the opacity of the sharpening layer
08:00 Sharpening in only one direction
09:50 What is Grain Merge doing?
11:00 How does this work?
14:50 Scripts at the http://registry.gimp.org

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Meet the GIMP Video Podcast by Rolf Steinort and Philippe Demartin is licensed under a Creative Commons Attribution-Share Alike 3.0 Germany License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.

Episode 129: Octave Sharpening Python Plugin

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This is the second time I try to get into Python scripting for GIMP. My script in the first show about scripting was simple, just saving some clicks. Now it is more complicated, variables, loops and floating points included. But no parrots!

You find a better version of the programs in the companion file. Following a tip in our Forum I included a Undo Group. So the action can be undone, a behaviour that should have been included from the start.

I mentioned some sources. Instant Python, the official Python Tutorial and the GIMP Python reference. Bert has a script page and a much better version of the Octave sharpening script.

Then we have a UnGIMP composition challenge on the Forum.

Have I forgotten some promised links? Please complain below!

Errata:

The loop counter in the companion file is set to 6 instead of 4. You can change it back or leave it.

Perhaps it is better to take the image size from drw instead of img. See the discussion in the forum. drw.height and drw.width should work also when the layer is smaller than the image.

Creative Commons License
Meet the GIMP Video Podcast by Rolf Steinort and Philippe Demartin is licensed under a Creative Commons Attribution-Share Alike 3.0 Germany License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.

Episode 095: Shrinking! (1)

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95

Again I steal an idea from the forum. It’s making fake tilt shift images. They look like images of model railway landscapes but are made from reality. Have a look at the forum for links to images by Bert and others.

I do half of the work in this podcast – planning the image and give the real world a plastic look. Next week I’ll add the focus blur that is so typical for macro shots.

But at the start I show that I have learned something from Philippe: Look carefully at an original. The image on the right is a H0 scale model in the sand on the Weser beach – real plastic.

The companion file contains the original shots – the xcf will follow next week.

The TOC

00:30 Fake tilt shift images
01:50 Analyzing a macro shot of a toy
05:30 The real image
06:30 What shall be in the focus?
13:00 Rotate before crop and resize
16:00 Inside out crop
17:30 Scaling down
18:00 Analyze the plastic look
19:30 Selective sharpening
24:30 Unsharp mask for getting the plastic look
28:50 Specular highlights

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Creative Commons Attribution-Share Alike 2.0 Germany License.

Episode 006: Selective sharpening

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Every digital image needs sharpening. But sharpening increases the noise in the image. In this episode I show a way to sharpen only the areas that need to be sharpened – the edges between different colours or levels of brightness. All the other parts of the image are left alone and so the noise stays down.

Sharpening should always be the very last thing you do with your image.

Picture for episode 006

Chris Marquard explained sharpening in Photoshop Corner No. 4 in his Tips from the Top Floor podcast.

I got the described method from the Gimp tutorial page.

Wikipedia describes the underlying process in this article about the unsharp mask. The links at the bottom of the page are very informative.

Meet the GIMP! is now listed in iTunes and Podcast Alley. If you like the show please let the people there know. ;-)
You can leave your comments on this blog, write me a or go to the Tips from the Top Floor Forum.

The TOC

00:22 Welcome
01:00 The original image
01:25 Why we want to selectively sharpen
02:38 Copy the layer and add a layer mask
04:00 Edge-Detect on the layer mask
06:40 Blur the layer mask
07:12 Increase contrast using curves
08:34 Sharpen the image
10:25 Fine tuning
14:35 How sharpening works
15:49 tips from the top floor
18:26 The End
TOC made by paynekj


Creative Commons License

This work is licensed under a
Creative Commons Attribution-Share Alike 2.0 Germany License.