The Graphical Library GEGLDeveloping Blackand White Images with GEGL Operations

Figure 4.9

Developing black-and-white images using the GEGL Operation mono-mixer

Figure 4.9

Developing black-and-white images using the GEGL Operation mono-mixer

The Generic Graphics Library (GEGL) has been integrated in GIMP with version 2.6. It is supposed to be expanded to ensure image editing with more than 8 bits per channel with GIMP. Some of the computation functions based on GEGL are already assembled in the GEGL Operation window , which can be found by choosing Tools > GEGL Operation.

In the Operation drop-down menu, there are three operations especially for converting images into black and white.

The mono-mixer is a simple function that automatically converts a color image into a grayscale image. It also offers the possibility of changing the brightness and contrast by modifying the RGB color values. With a little experience, the mono-mixer offers rather sophisticated results.

The results of the contrast-curve operation, on the other hand, are quite puzzling. This function also converts color images to grayscale, but modifying the values using the sliders doesn't change the rendering of the image. The question remains as to what can be adjusted with the sliders. The help function doesn't have any information either.

A far more sophisticated option is the c2g (color-to-gray) operation. It should be noted that this setting is very demanding on your hardware, as are most of the GEGL operations. My computer, mind you, an AMD Dual-Core Athlon 64 X2 3800 with 2 GB RAM, regularly took some time to process a 2 megapixel image. Nevertheless, the application is stable; you do get a result after quite some time. It is, however, difficult to handle, and every little adjustment leads the program to compute without giving you the option to adjust the value. At least you can be quite specific by entering the values on the right side. To some degree, you can edit low-resolution images with few pixels in real time. Still, every little step takes time. Overall, c2g is an interesting tool that in addition to controlling brightness and contrast can simulate film grain. As can be seen in figure 4.10 and figure 4.11, it is an interesting toy for those who like to experiment.

4.1 converting color images partly or entirely into grayscale images

Figure 4.10

The possibilities of black-and-white developing range from the developing of coarse grain and high contrasts, as can be seen here with the settings...

Figure 4.10

The possibilities of black-and-white developing range from the developing of coarse grain and high contrasts, as can be seen here with the settings...

Figure 4.11

.to the graphic relief effect.

CHAPTER 4

WORKING WITH BLACK-AND-WHITE AND COLOR IMAGES

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