Grayscale Images

In RGB color representation, (255, 255, 255) results in the brightest white, and (0, 0, 0) results in black. Any time the three intensities are equal, no color is emphasized and the result is a shade of gray. For example (128, 128, 128) would be a medium gray, (240, 240, 240) would be a bright gray approaching white, and (16, 16, 16) would be a dark gray not far from black.

A grayscale image is one in which the color palette contains only grays, evenly graduated from black (0, 0, 0) for pixel value 0, to white (255,255,255) for the highest possible pixel value. This means that in an 8-bit gray level image, the blue, green, and red intensities for each palette entry are equal to the pixel value. The color palette for an 8-bit gray level image is illustrated below:

	BLUE	GREEN	RED	Not Used
color 0	0	0	0	0
color 1	1	1	1	0
color 2	2	2	2	0
color 3	3	3	3	0
...	...	...	...	...
color 254	254	254	254	0
color 255	255	255	255	0

Some ImageGear image processing operations cannot be performed on 8i (8-bit color) images, because some colors that occur as a result of the processing may not be present in the image's color palette. For such operations, if the image is 8-bit, it must be 8-bit gray level.