RAS_PALETTE(5NCARG)

💖 RAS_PALETTE 💖

okay bestie, so this is the 5NCARG manual page for ras_palette — it's all about how palette files work for NCAR View. If you've ever wanted to know how colors get stored in a file so your imagery doesn't look like a sad gray blob, this is THE page. ✨

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🌸 NAME 🌸

ras_palette — format descriptions for palette files for NCAR View 🎨

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🎀 SYNOPSIS 🎀

palette_file.pal
palette_file.txt

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🦋 DESCRIPTION 🦋

NCAR View is that girl and she supports two formats for color palettes — a binary one and a textual one. Two options, both iconic, we love choices. 💅

binary format (the .pal one) 💾

The binary format is compatible with NCSA HDF, and ngl it must have a file extension of ".pal". Like, it's not optional, that's just the rules.

So the palette has a red table, a green table, and a blue table — each one holding 256 single unsigned byte entries. A 0 means no intensity for that color, and a 255 means full intensity. Slay.

In the file, the palette gets stored like this:

R0 R1 ... R255 G0 G1 ... G255 B0 B1 ... B255

for a total of 768 bytes. That's it, that's the whole thing, no cap. 🫶

textual format (the .txt one) 📝

The textual format can be made by a program or manually with a text editor — very DIY of it, we respect the hustle. It provides for 256 RGB entries but also allows for a sparse color table. And in that sparse case? The missing values get calculated from the ones you did give using linear interpolation. Math girlies rise up. 📈

Also, if unspecified, the 0 entry defaults to black and the 255 entry defaults to white. (Cute defaults, honestly.)

Each color palette entry has this format:

index_number red green blue

where index_number, red, green, and blue are all integers in the range 0 to 255. ⭐

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🌈 EXAMPLES 🌈

All of the examples below deal with textual color palettes. Just so we're clear. 💖

Setting Entries ✍️

• Set color index 0 to black.

0 0 0 0

• Set color index 255 to white.

255 255 255 255

Grayscale Ramp 🖤🤍

Let's suppose you have a file named "my.txt" and it has just two lines in it: the black entry and the white entry from above. This will produce a grayscale color palette, where the table starts at black and ramps up to white; and since only entries 0 and 255 are specified, the remaining indices are interpolated.

0 0 0 0
255 255 255 255

Note: An empty palette file (e.g. "empty.txt") is legal and, since the 0 index defaults to black and the 255 index to white, produces a grayscale ramp just as in the above example. Empty file but make it fashion. 💀✨

Temperature Color Scale 🌡️🔥

Let's suppose you want entry 0 to be black, and the remaining indices to start at 1 with a fully-saturated blue and shift linearly to 255 with a fully-saturated red. Only three entries are required in your file, "temp.txt".

0 0 0 0
1 0 0 255
255 255 0 0

The way that blue-to-red glow-up happens with literally three lines?? Obsessed. 😭💜

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👑 SEE ALSO 👑

rasview(1NCARG), rascat(1NCARG), rasgetpal(1NCARG), rassplit(1NCARG), rasls(1NCARG), ras_formats(5NCARG)

Go read those too bestie, they're all in the family. 🫶

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💀 BUGS/CAVEATS 💀

Color palettes are only useful with indexed-color imagery. That's the caveat, that's the tea. Don't come for me. 🙈

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📜 COPYRIGHT 📜

Copyright (C) 1987-2009 University Corporation for Atmospheric Research

The use of this Software is governed by a License Agreement.

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and that's the whole page, bestie!! this lil masterpiece is from the NCARG crew, dated January 1993, and yeah she's vintage but she ATE. 💅✨🎀 no cap, fr fr. bye mwah 😘💖