Hints for Working in Grayscale and RGB Modes

By default, GIMP works in RGB color mode, which supports the representation of approximately 16.7 million colors. This color mode supports all the tools available for manipulating colors or color values in an image.

In addition, GIMP offers the grayscale mode. Grayscale corresponds to a limited color palette of 256 gray levels, including black and white. All tools used to manipulate brightness and contrast levels are supported in grayscale mode. However, tools, filters, and options that directly manipulate colors are not supported in the grayscale mode. This means that certain tasks, such as the subsequent coloring of black-and-white images, must be performed in RGB color mode. So what is the point of working in grayscale mode?

There are occasions when the conversion of color images into grayscale images may be required for the following reasons:

• Technical concerns, such as, creating a selection on a high-contrast original document (although this task can be somewhat achieved by using a copied layer of an image).

• Optimization of an image's file size. Grayscale images have a maximum number of 256 colors, so changing to that mode will reduce the file size because less color information has to be saved.

Nevertheless, you'll normally be editing black-and-white photos in RGB mode. When an image is scanned as a grayscale image, it will initially be available in grayscale mode. Even so, it is recommended that you convert the image into RGB mode prior to editing it.

4.1 CONVERTING COLOR IMAGES PARTLY OR ENTIRELY INTO GRAYSCALE IMAGES

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