Converting Images into Blackand White Graphics

Figure 4.12

Using the Threshold function to achieve graphic effects in black-and-white

Figure 4.12

Using the Threshold function to achieve graphic effects in black-and-white

It is possible to convert images into pure black-and-white graphics with GIMP. Threshold is the quick-and-dirty function used to convert images and can be found in the Colors menu. It doesn't matter if the image is a color or grayscale image, it converts the image into a pure black-and-white graphical image. The only option for adjustment is the triangular slide control under the histogram, marking the point the contrast is inverted. The GEGL operation threshold (Tools > GEGL Operation) works in a similar fashion.

Threshold achieves this effect of black-and-white inversion by means of a value from which the inversion from black-and-white occurs but without considering gradients and shades of brightness. You obtain a pure black-and-white graphic image by inverting the image with the Indexed Colors mode (Image > Mode > Indexed), using Color dithering. The result is a simulation of brightness gradients through dithering (in this case, diffusion of black pixels to achieve grayscale simulation). In the Convert Image to Indexed Colors window, first select the option Use black-and-white (1-bit) palette. Then select Dithering, thereby selecting the method of diffusion. Experiment a little. The results depend on how much contrast the image had beforehand and which dithering you choose. If you want to dye your image afterward, you must adjust the RGB mode (Image > Mode) again. Otherwise, further editing isn't possible.

4.1 CONVERTING COLOR IMAGES PARTLY OR ENTIRELY INTO GRAYSCALE IMAGES

Figure 4.13

Using dithering in the Indexed Colors function to achieve a grayscale simulation

Figure 4.13

Using dithering in the Indexed Colors function to achieve a grayscale simulation

0 0

Post a comment