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List of monochrome and RGB color formats

From Wikipedia, the free encyclopedia

This list of monochrome and RGB palettes includes generic repertoires of colors (color palettes) to produce black-and-white and RGB color pictures by a computer's display hardware. RGB is the most common method to produce colors for displays; so these complete RGB color repertoires have every possible combination of R-G-B triplets within any given maximum number of levels per component.

Each palette is represented by a series of color patches. When the number of colors is low, a 1-pixel-size version of the palette appears below it, for easily comparing relative palette sizes. Huge palettes are given directly in one-color-per-pixel color patches.

For each unique palette, an image color test chart and sample image (truecolor original follows) rendered with that palette (without dithering) are given. The test chart shows the full 256 levels of the red, green, and blue (RGB) primary colors and cyan, magenta, and yellow complementary colors, along with a full 256-level grayscale. Gradients of RGB intermediate colors (orange, lime green, sea green, sky blue, violet, and fuchsia), and a full hue spectrum are also present. Color charts are not gamma corrected.

RGB 24bits palette sample image.jpg
RGB 24bits palette color test chart.png

These elements illustrate the color depth and distribution of the colors of any given palette, and the sample image indicates how the color selection of such palettes could represent real-life images. These images are not necessarily representative of how the image would be displayed on the original graphics hardware, as the hardware may have additional limitations regarding the maximum display resolution, pixel aspect ratio and color placement.

Implementation of these formats is specific to each machine. Therefore, the number of colors that can be simultaneously displayed in a given text or graphic mode might be different. Also, the actual displayed colors are subject to the output format used - PAL or NTSC, composite or component video, etc. - and might be slightly different. For simulated images and specific hardware and alternate methods to produce colors other than RGB (ex: composite), see the List of 8-bit computer hardware palettes, the List of 16-bit computer hardware palettes and the List of video game console palettes. For various software arrangements and sorts of colors, including other possible full RGB arrangements within 8-bit color depth displays, see the List of software palettes.


Monochrome palettes

These palettes only have some shades of gray, from black to white, both considered the most possible darker and lighter "grays", respectively. The general rule is that those palettes have 2n different shades of gray, where n is the number of bits needed to represent a single pixel.

Monochrome (1-bit grayscale)

Monochrome graphics displays typically have a black background with a white or light gray image, though green and amber monochrome monitors were also common. Such a palette requires only one bit per pixel.

Bilevel 1bit palette sample image.png
Bilevel 1bit palette color test chart.png
1-bit grayscale.gif

Where photo-realism was desired, these early computer systems had a heavy reliance on dithering to make up for the limits of the technology.

Bilevel 1bit palette sample image - gimp dithered.png
RGB 24bits palette color test chart - 1-bit dithered.png
Bilevel 1bit palette.png

In some systems, as Hercules and CGA graphic cards for the IBM PC, a bit value of 1 represents white pixels (light on) and a value of 0 the black ones (light off); others, like the Atari ST and Apple Macintosh with monochrome monitors, a bit value of 0 means a white pixel (no ink) and a value of 1 means a black pixel (dot of ink), which it approximates to the printing logic.

2-bit Grayscale

In a 2-bit color palette each pixel's value is represented by 2 bits resulting in a 4-value palette (22 = 4).

Grayscale 2bit palette sample image.png
Grayscale 2bit palette color test chart.png
2-bit grayscale.gif

2-bit dithering:

Grayscale 2bit palette sample image - gimp dithered.png
RGB 24bits palette color test chart - 2-bit dithered.png

It has black, white and two intermediate levels of gray as follows:

Grayscale 2bit palette.png

A monochrome 2-bit palette is used on:

4-bit Grayscale

In a 4-bit color palette each pixel's value is represented by 4 bits resulting in a 16-value palette (24 = 16):

Grayscale 4bit palette sample image.png
Grayscale 4bit palette color test chart.png
4-bit grayscale.gif

4-bit grayscale dithering does a fairly good job of reducing visible banding of the level changes:

Grayscale 4bit palette sample image - gimp dithered.png
RGB 24bits palette color test chart - 4-bit gray dithered.png
Grayscale 4bit palette.png

A monochrome 4-bit palette is used on:

8-bit Grayscale

Grayscale 8bits palette sample image.png
Grayscale 8bits palette color test chart.png
8-bit grayscale.gif

In an 8-bit color palette each pixel's value is represented by 8 bits resulting in a 256-value palette (28 = 256). This is usually the maximum number of grays in ordinary monochrome systems; each image pixel occupies a single memory byte.

Grayscale 8bits palette.png

Most scanners can capture images in 8-bit grayscale, and image file formats like TIFF and JPEG natively support this monochrome palette size.

Alpha channels employed for video overlay also use (conceptually) this palette. The gray level indicates the opacity of the blended image pixel over the background image pixel.

Dichrome palettes

16-bit RG palette

RG 16bits palette sample image.png
RG 16bits palette color test chart.png
Redgreen.png
Additive RG Additive RG color palette

16-bit RB palette

RB 16bits palette sample image.png
RB 16bits palette color test chart.png
Redblue.png
Additive RB Additive RB color palette

16-bit GB palette

GB 16bits palette sample image.png
GB 16bits palette color test chart.png
Greenblue.png
Additive GB Additive GB color palette

Regular RGB palettes

Here are grouped those full RGB hardware palettes that have the same number of binary levels (i.e., the same number of bits) for every red, green and blue components using the full RGB color model. Thus, the total number of colors are always the number of possible levels by component, n, raised to a power of 3: n×n×n = n3.

3-bit RGB

RGB 3bits palette sample image.png
RGB 3bits palette color test chart.png
3-bit RGB Cube.gif

3-bit RGB dithering:

RGB 24bits palette sample image - 3-bit RGB.png
RGB 24bits palette color test chart - 3-bit RGB dithered.png

Systems with a 3-bit RGB palette use 1 bit for each of the red, green and blue color components. That is, each component is either "on" or "off" with no intermediate states. This results in an 8-color palette ((21)3 = 23 = 8) that have black, white, the three RGB primary colors red, green and blue and their correspondent complementary colors cyan, magenta and yellow as follows:

RGB 3bits palette.png

The color indices vary between implementations; therefore, index numbers are not given.

The 3-bit RGB palette is used by:

6-bit RGB

RGB 6bits palette sample image.png
Ega palette color test chart.png
6-bit RGB Cube.gif

Systems with a 6-bit RGB palette use 2 bits for each of the red, green, and blue color components. This results in a (22)3 = 43 = 64-color palette as follows:

RGB 6bits palette.png

6-bit RGB systems include the following:

9-bit RGB

RGB 9bits palette sample image.png
RGB 9bits palette color test chart.png
9-bit RGB Cube.gif

Systems with a 9-bit RGB palette use 3 bits for each of the red, green, and blue color components. This results in a (23)3 = 83 = 512-color palette as follows:

RGB 9bits palette.png

9-bit RGB systems include the following:

12-bit RGB

RGB 12bits palette sample image.png
RGB 12bits palette color test chart.png
12-bit RGB Cube.gif

Systems with a 12-bit RGB palette use 4 bits for each of the red, green, and blue color components. This results in a (24)3 = 163 = 4096-color palette. 12-bit color can be represented with three hexadecimal digits, also known as shorthand hexadecimal form, which is commonly used in web design. The palette is as follows:

RGB 12bits palette.png

12-bit RGB systems include the following:

The Allegro library supported in the (legacy) version 4, an emulated 12-bit color mode example code ("ex12bit.c"), using 8-bit indexed color in VGA/SVGA. It used two pixels for each emulated pixel, paired horizontally, and a specifically adapted 256-color palette. One range of the palette was many brightnesses of one primary color (say green), and another range of the other two primaries mixed together at different amounts and brightnesses (red and blue). It effectively reduced the horizontal resolution by half, but allowed a 12-bit "true color" in DOS and other 8-bit VGA/SVGA modes. The effect also somewhat reduced the total brightness of the screen.[3]

Allegro 4 - ex12bit.c.png

15-bit RGB

RGB 15bits palette sample image.png
RGB 15bits palette color test chart.png
15-bit RGB Cube.gif

Systems with a 15-bit RGB palette use 5 bits for each of the red, green, and blue color components. This results in a (25)3 = 323 = 32,768-color palette (commonly known as Highcolor) as follows:

RGB 15bits palette.png

15-bit systems include:

18-bit RGB

RGB 18bits palette sample image.png
RGB 18bits palette color test chart.png
18-bit RGB Cube.gif

Systems with an 18-bit RGB palette use 6 bits for each of the red, green, and blue color components. This results in a (26)3 = 643 = 262,144-color palette as follows:

RGB 18bits palette.png

18-bit RGB systems include the following:

24-bit RGB

RGB 24bits palette sample image.jpg
RGB 24bits palette color test chart.png

Often known as truecolor and millions of colors, 24-bit color is the highest color depth normally used, and is available on most modern display systems and software. Its color palette contains (28)3 = 2563 = 16,777,216 colors. 24-bit color can be represented with six hexadecimal digits.

All 16,777,216 colors (downscaled, click image for full resolution).
All 16,777,216 colors (downscaled, click image for full resolution).

The complete palette (shown above) needs a squared image of 4,096 pixels wide (50.33 MB uncompressed), and there is not enough room in this page to show it at full.

This can be imagined as 256 stacked squares like the following, every one of them having the same given value for the red component, from 0 to 255.

The color transitions in these patches must be seen as continuous. If color stepping (banding) inside is visible, then probably the display is set to a Highcolor (15- or 16- bits RGB, 32,768 or 65,536 colors) mode or lesser.

RGB 24bits palette R0.png

Red = 0
RGB 24bits palette R85.png

Red = 85 (1/3 of 255)
RGB 24bits palette R170.png

Red = 170 (2/3 of 255)
RGB 24bits palette R255.png

Red = 255
All 16,777,216 colors in the same pattern as the other RGB palettes above (downscaled, click image for full resolution).
All 16,777,216 colors in the same pattern as the other RGB palettes above (downscaled, click image for full resolution).

This is also the number of colors used in true color image files, like Truevision TGA, TIFF, JPEG (the last internally encoded as YCbCr) and Windows Bitmap, captured with scanners and digital cameras, as well as those created with 3D computer graphics software.

24-bit RGB systems include:

30-bit RGB

Some newer graphics cards support 30-bit RGB and higher. Its color palette contains (210)3 = 10243 = 1,073,741,824 colors. However, there are few operating systems or applications that support this mode yet. For some people, it may be hard to distinguish between higher color palettes than 24-bit color offers. However, the range of luminance, or gray scale, offered in a 30-bit color system would have 1,024 levels of luminance rather than the 256 of the common standard 24-bit, to which the human eye is more sensitive than to hue. This reduces the banding effect for gradients across large areas.[4]

Non-regular RGB palettes

These also are full RGB palette repertories, but either they do not have the same number of levels for every red, green and blue components, or they are bit levels based. Nevertheless, all of them are used in very popular personal computers.

For further details on color palettes for these systems, see the article List of 8-bit computer hardware palettes.

4-bit RGBI

RGBI 4bits palette sample image.png
RGBI 4bits palette color test chart.png

The 4-bit RGBI palette is similar to the 3-bit RGB palette but adds one bit for intensity. This allows each of the colors of the 3-bit palette to have a dark and bright variant, potentially giving a total of 23×2 = 16 colors. However, some implementations had only 15 effective colors due to the "dark" and "bright" variations of black being displayed identically.

This 4-bit RGBI schema is used in several platforms with variations, so the table given below is a simple reference for the palette richness, and not an actual implemented palette. For this reason, no numbers are assigned to each color, and color order is arbitrary.

RGBI 4bits palette.png

Note that "dark white" is a lighter gray than "bright black" in this example.

IBM PC graphics

Cga palette color test chart.png

A common use of 4-bit RGBI was on IBM PCs and compatible computers that used a 9-pin DE-9 connector for color output. These computers used a modified "dark yellow" color that appeared to be brown. On displays designed for the IBM PC, setting a color "bright" added ⅓ of the maximum to all three channels' brightness, so the "bright" colors were whiter shades of their 3-bit counterparts. Each of the other bits increased a channel by ⅔, except that dark yellow had only ⅓ green and was therefore brown instead of ochre.[5]

PC graphics standards using this RGBI mode include:

The CGA palette is also used by default by IBM's later EGA, MCGA, and VGA graphics standards for backward compatibility, but these standards allow the palette to be changed, since they either provide extra video signal lines or use analog RGB output.

The MOS Technology 8563 and 8568 Video Display Controller chips used on the Commodore 128 series for its 80-column mode (and the unreleased Commodore 900 workstation) also used the same palette used on the IBM PC, since these chips were designed to work with existing CGA PC monitors.

Other uses

Other systems using a variation of the 4-bit RGBI mode include:

  • The ZX Spectrum series of computers, which lack distinct "dark" and "light" black colors, resulting in an effective 15-color palette.[6]
  • The Sharp MZ-800 series computers.[7]
  • The Thomson MO5 and TO7 where the intensity bit created a variation of both brightness and saturation.
  • The Mattel Aquarius and AlphaTantel where the intensity bit created a variations of brightness and saturation.

3-level RGB

AmstradCPC palette sample image.png
AmstradCPC palette color test chart.png

3-level RGB dithering:

3 Level RGB Dither example.png
3-Level RGB Palette Color Test Chart Dither.png

The 3-level, or 1-trit (NOT 3 bits) RGB uses three levels for every red, green and blue color component, resulting in a 33 = 27 colors palette as follows:

3-Level-RGB-Colors.svg

This palette is used by:

  • The Amstrad CPC 464 series of personal computers excluding the Plus models (up to 16 colors simultaneously)
  • The Toshiba Pasopia 7 (uses hardware dithering to simulate intermediate color intensities, based on a mix of the full intensity RGB primaries.[8])

8-bit RGB (also known as 3-3-2 bit RGB and 8-8-4 bit RGB)

MSX2 Screen8 palette sample image.png
MSX2 Screen8 palette color test chart.png

The 3-3-2 bit RGB use 3 bits for each of the red and green color components, and 2 bits for the blue component, due to the eyes having lesser sensitivity to blue. This results in an 8×8×4 = 256-color palette as follows:

MSX2 Screen8 palette.png

This palette is used by

  • The MSX2 series of personal computers.
  • Palette 4 of the IBM PGC (palette 2 gives 2-3-3 bit RGB and palette 3 gives 3-2-3 bit RGB).
  • Enterprise Computer
  • VGA built-in output of the Digilent Inc. NEXYS 2, NEXYS 3 and BASYS2 FPGA boards.
  • The Uzebox gaming console
  • SGI Indy 8-bit XL graphics
  • The Tiki 100 personal computer (only 16 colors can be displayed simultaneously)
  • Wear OS smartwatches with ambient displays (only 16 colors can be displayed simultaneously)

16-bit RGB

RGB 16bits palette sample image.png
RGB 16bits palette color test chart.png

Most modern systems support 16-bit color. It is sometimes referred to as Highcolor (along with the 15-bit RGB), medium color or thousands of colors. It utilizes a color palette of 32×64×32 = 65,536 colors. Usually, there are 5 bits allocated for the red and blue color components (32 levels each) and 6 bits for the green component (64 levels), due to the greater sensitivity of the common human eye to this color. This doubles the 15-bit RGB palette.

The 16-bit RGB palette using 6 bits for the green component:

RGB 16bits palette.png

The Atari Falcon and the Extended Graphics Array (XGA) for IBM PS/2 use the 16-bit RGB palette.

It must be noticed that not all systems using 16-bit color depth employ the 16-bit, 32-64-32 level RGB palette. Platforms like the Sharp X68000 home computer or the Neo Geo video game console employs the 15-bit RGB palette (5 bits are used for red, green, and blue), but the last bit specifies a less significant intensity or luminance. The 16-bit mode of the Truevision TARGA/AT-Vista/NU-Vista graphic cards and its associated TGA file format also uses 15-bit RGB, but it devotes its remaining bit as a simple alpha channel for video overlay. The Atari Falcon can also be switched into a matching mode by setting of an "overlay" bit in the graphics processor mode register when in 16-bit mode, meaning it can actually display in either 15- or 16-bit color depth depending on application.

Color palette comparison side-by-side

Basic color palettes

4-bit grayscale

0x0 0x1 0x2 0x3 0x4 0x5 0x6 0x7 0x8 0x9 0xA 0xB 0xC 0xD 0xE 0xF

3-bit RGB

0x0 0x1 0x2 0x3 0x4 0x5 0x6 0x7

4-bit RGBI

3 level RGB

Notes

  • Color values in bold exist in 2-bit (four color) grayscale palette. Color values in very bold exist in 1-bit, monochrome palette.
  • In 4-bit RGBI, dark colors have 23rds intensity of the bright colors, not 12.

Advanced color palettes

8-bit RGB (VGA)

[9]

0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F
0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F
0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x29 0x2A 0x2B 0x2C 0x2D 0x2E 0x2F
0x30 0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 0x3C 0x3D 0x3E 0x3F
0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F
0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 0x5A 0x5B 0x5C 0x5D 0x5E 0x5F
0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0x6D 0x6E 0x6F
0x70 0x71 0x72 0x73 0x74 0x75 0x76 0x77 0x78 0x79 0x7A 0x7B 0x7C 0x7D 0x7E 0x7F
0x80 0x81 0x82 0x83 0x84 0x85 0x86 0x87 0x88 0x89 0x8A 0x8B 0x8C 0x8D 0x8E 0x8F
0x90 0x91 0x92 0x93 0x94 0x95 0x96 0x97 0x98 0x99 0x9A 0x9B 0x9C 0x9D 0x9E 0x9F
0xA0 0xA1 0xA2 0xA3 0xA4 0xA5 0xA6 0xA7 0xA8 0xA9 0xAA 0xAB 0xAC 0xAD 0xAE 0xAF
0xB0 0xB1 0xB2 0xB3 0xB4 0xB5 0xB6 0xB7 0xB8 0xB9 0xBA 0xBB 0xBC 0xBD 0xBE 0xBF
0xC0 0xC1 0xC2 0xC3 0xC4 0xC5 0xC6 0xC7 0xC8 0xC9 0xCA 0xCB 0xCC 0xCD 0xCE 0xCF
0xD0 0xD1 0xD2 0xD3 0xD4 0xD5 0xD6 0xD7 0xD8 0xD9 0xDA 0xDB 0xDC 0xDD 0xDE 0xDF
0xE0 0xE1 0xE2 0xE3 0xE4 0xE5 0xE6 0xE7 0xE8 0xE9 0xEA 0xEB 0xEC 0xED 0xEE 0xEF
0xF0 0xF1 0xF2 0xF3 0xF4 0xF5 0xF6 0xF7 0xF8 0xF9 0xFA 0xFB 0xFC 0xFD 0xFE 0xFF

See also

References

  1. ^ "Commodore: A2024". Archived from the original on 2012-03-02.
  2. ^ "Download - Parallax" (PDF).
  3. ^ "ex12bit - How to fake a 12-bit truecolor mode on an 8-bit card. Allegro game programming library. - Linux Man Pages (3)". www.systutorials.com.
  4. ^ "Gradients on TVs: Color bit depth".
  5. ^ "KeyJ's Blog : Blog Archive » Color Generation in IBM CGA, EGA and VGA". Retrieved 2020-05-26.
  6. ^ paleotronic (2018-09-29). "Colour Clash: The Engineering Miracle of the Sinclair ZX Spectrum". Paleotronic Magazine. Retrieved 2020-05-26.
  7. ^ "Sharp MZ-800 - MCbx". oldcomputer.info. Retrieved 2020-05-26.
  8. ^ "Pasopia7 (Pa7007)".
  9. ^ "VGA Color Palettes". Fountain Ware. Retrieved 24 November 2021.
This page was last edited on 24 November 2021, at 05:16
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