black & white

Maximize Local Contrast

Roy Johnson — Wed, 01 Jul 2009 18:36:27 +0200

FX-Foundry/Photo/Enhancement/Maximize Local Contrast... Like Stretch Contrast, but instead of using the minimum and maximum pixel values from the entire image, uses the minimum and maximum in the vicinity of a pixel to compute its new value. Takes a while to run, but really brings out textures. Result is a Grain Merge layer that adjusts values of the original image.

This filter operates on the visible image, not on a layer or selection.

Radius indicates how wide a pixel's influence is. If you choose too small a value, adjustment will be too localized and the image will look patchy. Larger values take a bit longer to run.

Threshold indicates how many neighboring gray values above and below a value can be treated as the same, in finding minimum and maximum values. Purely a speed trade-off. Using very low values will make it very slow. Too high values will cause visible "steps" in color values. The latest version does not include threshold, but the older version is still available.

"Feather Haloes" helps smooth out haloes around high-contrast areas.

"Keep Min and Max Layers" leaves the intermediate layers in the stack so you can look at them if you're interested.

Update (21 Jul 2009):

New algorithm that works right without any compromises for speed. No scaling, no threshold. It does take a bit of time on large images; 45 seconds for a 1500x2000 pixel image on a modern but not especially powerful PC. The full 8-megapixel image took about 3 minutes. Most of the time is spent on grow-selection, so don't be alarmed when the progress meter seems to hang up for a while. There are just two grows and two feathers to do.
If you want a speed compromise, I've added Scaledown factor, which will reduce the time spent in selection a lot, but will add some time for scaling the image. There's essentially no loss of quality. Recommended for especially large images.

Updates (13 Jul 2009):

SPEED! Mapping of Min and Max is done on scaled-down layers. Now even large images can be done in reasonable time.
Feather haloes feature for more reasonable results on high-contrast images and images with big flat areas
Layer mask keeps narrow-contrast areas under control

Updates (9 Jul 2009):

Fixed the bug that left strange artifacts in the image.
Changed radius to work as a % of image size (maximum dimension)
Increased feathering and added limits to min and max layers to control haloes around small, high-contrast features
Got rid of sample images. Will find better examples.

New Engrave plugin

leware — Thu, 09 Apr 2009 15:04:15 +0200

This plugin is an alternative to the existing Engrave plugin supplied with GIMP. Basically, the plug-in transforms a grayscale image into a series of horizontal lines of varying widths. For example, the following (small) image

can be transformed into:

(stand back 10-20 feet).

Full description at: http://pages.infinit.net/leware/engrave.html .

G'MIC plug-in

dtschump — Tue, 13 Jan 2009 14:16:31 +0100

The G'MIC plug-in for GIMP defines a set of various filters, including artistic filters, image denoising and enhancement, 3D renderers, etc.. It is a quite large plug-in, integrating a lot of different effects to apply.

This plug-in is able to update his list of filter definitions from the Internet (so it improves itself over time), as well as allows any user to add its own custom filters in it.
It has been written by the author of the GREYCstoration algorithm (used for image denoising). It is actually intended to replace it in a near future.

Download G'MIC for Windows 32 bits

Here is one screenshot of the plug-in in action, as well as a result of filter application :

Filtered BW

Luke — Sun, 10 Aug 2008 16:08:12 +0200

This script converts color images to B&W using channel mixer settings,
which simulate the use of color filters in B&W photography. It allows to choose many predefined filters and set their intensity. Previously posted to old registry in July 2006, now updated to work with GIMP 2.4. Avoid setting intensity to 1, besause it totally filters one of RGB channels and increases noise.

BW Labs

baruchel — Sat, 21 Jun 2008 22:28:21 +0200

This is another script for converting a picture to black & white. The decompose plugin must to be available. The way of converting the picture is rather different than what other plugins do. Two different luminance layers are mixed according to a mask made with a saturation layer. Six different combinations are provided. Functions are available under the menu script-fu/Photography/BW Labs.

Digital Negative Calibration Pattern

isindir — Thu, 20 Mar 2008 23:12:00 +0100

Digital Negative Calibration Pattern - creates B&W calibration pattern. Menu Item is placed in Gimp main window Xtn -> Script-fu -> Utils

Black&White

eg — Mon, 07 Jan 2008 14:14:58 +0100

Implement several different black and white conversions including color filters

More information:

http://epaperpress.com/psphoto/
http://www.thelightsrightstudio.com