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How do I print a 256-colour test pattern in my terminal?

I want to check that my terminal correctly supports 256 colours.

256-colour test pattern

To get the below image, use:

curl -s https://gist.githubusercontent.com/HaleTom/89ffe32783f89f403bba96bd7bcd1263/raw/ | bash

The gist bash/zsh code is shellcheck clean, and also supports "Look Ma, no subprocesses!".

Alternatively, for a bash quicky:

for i in {0..255} ; do

    printf "x1b[48;5;%sm%3de[0m " "$i" "$i"

    if (( i == 15 )) || (( i > 15 )) && (( (i-15) % 6 == 0 )); then

        printf "n";

    fi

done

For total overkill, the granddaddy of the lot is terminal-colors, a 572-line script with multiple output formats.

You can also print a true color (24-bit) test pattern.

I found a nice Python script for that on GitHub written by Justin Abrahms which also prints the hex codes of the colours.

Download the script to current working directory

wget https://gist.githubusercontent.com/justinabrahms/1047767/raw/a79218b6ca8c1c04856968d2d202510a4f7ec215/colortest.py

give it execute permission

chmod +x colortest.py

Run it:

./colortest.py

Here's the script in full in case of link-rot:

#!/usr/bin/env python

# Ported to Python from http://www.vim.org/scripts/script.php?script_id=1349



print "Color indexes should be drawn in bold text of the same color."

print



colored = [0] + [0x5f + 40 * n for n in range(0, 5)]

colored_palette = [

    "%02x/%02x/%02x" % (r, g, b) 

    for r in colored

    for g in colored

    for b in colored

]



grayscale = [0x08 + 10 * n for n in range(0, 24)]

grayscale_palette = [

    "%02x/%02x/%02x" % (a, a, a)

    for a in grayscale 

]



normal = "33[38;5;%sm" 

bold = "33[1;38;5;%sm"

reset = "33[0m"



for (i, color) in enumerate(colored_palette + grayscale_palette, 16):

    index = (bold + "%4s" + reset) % (i, str(i) + ':')

    hex   = (normal + "%s" + reset) % (i, color)

    newline = 'n' if i % 6 == 3 else ''

    print index, hex, newline, 

While not quite a "test pattern", I have xterm-color-chooser:

Yet another script, written by me, is located in the VTE repository: https://git.gnome.org/browse/vte/plain/perf/256test.sh?h=vte-0-38.

It requires a window of 120-ish or more columns, but arranges the colors of the 6x6x6 cube nicely and compactly. The first digits of the indices are stripped for compactness, you can easily figure them out. The vertical bars provide you the ability to examine the exact RGB of the foreground color without antialiasing kicking in (as it does at the digits).

The top of the output (not shown in the screenshot below) demonstrates the craziness that goes around with the bold vs. bright ambiguity, namely that the boldness escape sequence combined with one of the legacy 8 colors' escape sequence for the foreground also switches to the bright counterpart color, whereas with the new style (256-color capable) escape sequences this is no longer the case, not even for the first 8 colors. At least that's how xterm and VTE (GNOME Terminal etc.) behave.

This screenshot shows about half of the output:

Perhaps superfluous but I've written a version that prints the 256 colors using the background with automatic shell width detection so the colors are more easily visible.

https://gist.github.com/WoLpH/8b6f697ecc06318004728b8c0127d9b3

#!/usr/bin/env python

from __future__ import print_function



import os

import shutil

import subprocess





def get_width(default=80):

    '''Attempt to detect console width and default to 80'''

    try:

        columns, rows = shutil.get_terminal_size()

    except AttributeError:

        try:

            _, columns = subprocess.check_output(['stty', 'size']).split()

        except OSError:

            columns = os.environ.get('COLUMNS', default)



    columns = int(columns) - 77

    # Since we have 6 columns with 1 space on each side, we can increment the

    # size for every 12 extra columns

    return max(0, columns / 12)





# Loosely based on https://gist.github.com/justinabrahms/1047767

colored = [0] + list(range(95, 256, 40))

colored_palette = [

    (r, g, b)

    for r in colored

    for g in colored

    for b in colored

]





grayscale_palette = [(g, g, g) for g in range(8, 240, 10)]





esc = '33['

# Reset all colors sequence

reset = esc + '0m'

# Regular color

normal = esc + '38;5;{i}m'

# Bold color

bold = esc + '1;' + normal

# Background color

background = esc + '48;5;{i}m'



pattern = (

    '{normal}{background}{padding:^{width}}{i:^3d} '  # pad the background

    '{r:02X}/{g:02X}/{b:02X}'  # show the hex rgb code

    '{padding:^{width}}'  # pad the background on the other side

    '{reset}'  # reset again

)



base_context = dict(reset=reset, padding='', width=get_width())



for i, (r, g, b) in enumerate(colored_palette + grayscale_palette, 16):

    context = dict(i=i, r=r, g=g, b=b, color=r + g + b, **base_context)

    context.update(bold=bold.format(**context))

    context.update(background=background.format(**context))



    # Change text color from black to white when it might become unreadable

    if max(r, g, b) > 0xCC:

        context.update(normal=normal.format(i=0))

    else:

        context.update(normal=normal.format(i=255))



    print(pattern.format(**context), end='')



    # Print newlines when needed

    if i % 6 == 3:

        print()

    else:

        print(' ', end='')