indexed color

(redirected from Named color)

indexed color

A method of compressing an image that enables 8 bits per pixel to look almost as good as 24 bits per pixel. The technique determines the 256 most frequently used colors in the image and creates a color lookup table, also called a "color map" or "color palette," that is stored with the image. Rather than each pixel in the image having all three RGB colors (one 8-bit red, one 8-bit green and one 8-bit blue), each pixel contains one 8-bit number that indexes into the 256-color lookup table, which contains the RGB values (see illustration below).

It Used to Be a Major Problem
When early computer screens were commonly limited to 256 colors, indexed color methods were essential. Even then, two indexed photos on screen at the same time with vastly different color schemes would overload the hardware's color capacity and cause images to display improperly. Today, computer hardware easily renders full 24-bit color, but 8-bit indexed images are still widely used to save bandwidth and storage space. See color depth, color palette and color lookup table.


Color Palette Index
The pixels in the image contain index numbers that point to the RGB value in the color lookup table. The RGB values are the ones used by the display system.







24-Bit Vs. 8-Bit
Indexed color images can look nearly identical to their 24-bit originals, because the 256 most frequently used colors are identified. The 256-color palette (top) was created in Photoshop from the original 24-bit image (left) to generate the image as 8 bits (right).


24-Bit Vs. 8-Bit
Indexed color images can look nearly identical to their 24-bit originals, because the 256 most frequently used colors are identified. The 256-color palette (top) was created in Photoshop from the original 24-bit image (left) to generate the image as 8 bits (right).
References in periodicals archive ?
And, even though Emerald has been named color of the year, keep a sharp eye out for Monaco Blue as spring's go-to color.
Named Color Replacement, offered standard on these MFPs, is designed for the many businesses that require precise color matching when producing branded materials.
You can't help seeing yourself, elbow cocked, a Crayola of some newly named color squeaking a wax corona around the face of a flower, mother next door, father at work, brothers and sisters outside terrorizing the white chickens, the house quiet as a boat on a pond.
The columns, as well as the reception desk, are surfaced in Corian solid surfaces, in the engagingly named color "Hot.
Delighted Mandy Allwood and proud dad Paul Hudson took the baby they've named Color home for the first time yesterday.
The "BERTL's Best" award named Color Access Policy Manager the "Best Manufacturer-Specific Approach to Managing Color Printing Costs.
color system and Lexmark Named Color Replacement true color matching.
Patients with schizophrenia named color patches most sluggishly when they had only a 50-millisecond head start on clashing words.
Equipped standard with Lexmark Named Color Replacement, businesses can store pre-defined colors on the devices to ensure precise and consistent color matching for branded materials.
Also bundled with the Konica Minolta bizhub C450 is Fiery Spot-On(R), which enables accuracy and consistency and helps manage named color and corporate colors.
The FR-S Concept is layered in rich coats of Code Red, the appropriately named color that consists of a custom blend of candy and a developmental additive from BASF called Mearlite SSQ.
Also available is Fiery Spot-On(R), which enables accuracy and consistency and helps manage named color and corporate colors.