File:IBM16 Palette Map.png
Original file (515 × 3,089 pixels, file size: 34 KB, MIME type: image/png)
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Summary
DescriptionIBM16 Palette Map.png | The IBM16 (CGA text modes, EGA smaller graphics modes) palette shown in relation both to its own 4-bit mapping and to the full 2 bits per sample of the CGA and EGA monitor circuitry (the 4-level, 64-colour palette from which EGA can pick any colour in its large graphics mode). To the left are the colour swatches with the 6-bit binary number representing the intensities of the Red, Green and Blue samples with regard to the full palette; to the right are 4-bit arrays of Intensity, Red, Green and Blue flags signalling the particular colour in the IBM16 subset. |
Date | 22 May 2006 (original upload date) |
Source | No machine-readable source provided. Own work assumed (based on copyright claims). |
Author | No machine-readable author provided. Shlomital~commonswiki assumed (based on copyright claims). |
Image information
Portable Network Graphics image, 515 pixels wide, 3089 pixels high, 8 bits per sample, RGB with alpha channel, 3780 pixels per metre (96 pixels per inch) resolution, 1/2.2 (0.45455) gamma, sRGB with relative colorimetric rendering intent, background colour #000000. Created with The GIMP 2.2.8, Netpbm 10.27.0 and pngcrush 1.5.10 on Tuesday the 23rd of May 2006.
Technical notes
With a range of 0–3, the values for Red, Green and Blue (on the left side) can be off, one third, two thirds or full (intensity of 0, 1/3, 2/3, 1). Obviously, having recurring decimals, it would not be practical to draw those numbers in the image itself; and vulgar fractions would be too similar to the binary values to be worth it (the binary number converted to decimal and divided by 3 gives the intensity). The stepping should be upscaled to the target bit-depth, which in this image is 8 bits per sample, giving 0 (hexadecimal 00), 85 (55), 170 (AA) and 255 (FF). The values 84 (54), 168 (A8) and 252 (FC) you see ever so often are the result of doing, from a 6-bit value, left-shift + zero-fill instead of linear scaling or left bit replication:
101010 (2A) → 10101010 (AA) : correct value 101010 (2A) → 10101000 (A8) : rounding error
See also the section Sample depth scaling of ISO/IEC 15948:2003 (section 12.5 on the W3C edition).
Orthopraxy
For any PNG screenshot from MS-DOS that uses the IBM16 palette or a subset of it, ie any CGA or EGA image (but not VGA), it is recommended to add an sBIT (significant bits) chunk with a value of 2 for each of Red, Green and Blue. In addition, the colour values should be checked for accuracy and fixed if erroneous (see above for the most common inaccuracy).
Other versions
- Image:IBM16_Palette_Map-reduced.png is a reduced-colour version (no antialising, palette with only one transparency entry) for decoders that ignore the alpha channel or generally for where resources are short.
Licensing
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License.http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue |
This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. | ||
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This licensing tag was added to this file as part of the GFDL licensing update.http://creativecommons.org/licenses/by-sa/3.0/CC BY-SA 3.0Creative Commons Attribution-Share Alike 3.0truetrue |
- You are free:
- to share – to copy, distribute and transmit the work
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- attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
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Items portrayed in this file
depicts
22 May 2006
File history
Click on a date/time to view the file as it appeared at that time.
Date/Time | Thumbnail | Dimensions | User | Comment | |
---|---|---|---|---|---|
current | 21:37, 1 September 2013 | 515 × 3,089 (34 KB) | Lunavorax | Compressed using PNGOUT and PNGCRUSH. | |
20:28, 23 May 2006 | 515 × 3,089 (38 KB) | Shlomital~commonswiki | new version: added #C0C0C0 borders | ||
22:39, 22 May 2006 | 512 × 3,072 (38 KB) | Shlomital~commonswiki | |||
19:14, 22 May 2006 | 512 × 3,264 (39 KB) | Shlomital~commonswiki | IBM16 palette shown in two relations |