feat: first version

.clang-format

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+---
+BasedOnStyle: Mozilla
+ColumnLimit: 80
+IndentWidth: 4
+UseTab: Never
+---
+Language: Cpp
+AllowShortIfStatementsOnASingleLine: Never
+BreakBeforeBraces: Attach
+AllowShortBlocksOnASingleLine: true
+AllowShortCaseLabelsOnASingleLine: true
+AllowShortFunctionsOnASingleLine: Inline
+DerivePointerAlignment: false
+PointerAlignment: Right

.gitattributes

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+*.h linguist-language=C
+*.sh linguist-generated
+Makefile linguist-generated

.github/FUNDING.yml

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+github: rodrigodornelles

.github/workflows/CI.yml

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+name: ci
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  clang-format:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        uses: actions/checkout@v2
+      - 
+        run: clang-format --dry-run --Werror --verbose rgb_to_xterm256.h
+      - 
+        run: clang-format --dry-run --Werror --verbose tools/pride.c
+
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        uses: actions/checkout@v2
+      - 
+        run: make test

.gitignore

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+*.out
+*.exe
+*.zip
+*.txt
+!LICENSE.txt
+pride
+html/
+latex/
+DS_Store
+Thumbs.db

LICENSE.txt

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+
+            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+                    Version 2, December 2004
+
+ Copyright (C) 2024 Rodrigo Dornelles
+
+ Everyone is permitted to copy and distribute verbatim or modified
+ copies of this license document, and changing it is allowed as long
+ as the name is changed.
+
+            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. You just DO WHAT THE FUCK YOU WANT TO.

rgb_to_xterm256.h

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+unsigned char
+rgb_to_xterm256(unsigned char r, unsigned char g, unsigned char b) {
+
+    unsigned int color_id = 0;
+    unsigned char half_color = (r >= 0x80 && r < 0x87) << 2 |
+                               (g >= 0x80 && g < 0x87) << 1 |
+                               (b >= 0x80 && b < 0x87);
+
+    static const unsigned char gray_brightness[] = {
+        0x00, 0x08, 0x12, 0x1c, 0x26, 0x30, 0x3a, 0x44, 0x4e, 0x58, 0x5f,
+        0x62, 0x6c, 0x76, 0x80, 0x87, 0x8a, 0x94, 0x9e, 0xa8, 0xaf, 0xb2,
+        0xbc, 0xc0, 0xc6, 0xd0, 0xd7, 0xda, 0xe4, 0xee, 0xff
+    };
+
+    static const unsigned char gray_colors[] = {
+        0x00, 0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef, 0xf0, 0x3b,
+        0xf1, 0xf2, 0xf3, 0xf4, 0x66, 0xf5, 0xf6, 0xf7, 0xf8, 0x91, 0xf9,
+        0xfa, 0x07, 0xfb, 0xfc, 0xbc, 0xfd, 0xfe, 0xff, 0x0f
+    };
+
+    static const unsigned char term_colors[] = { 0x04, 0x02, 0x06,
+                                                 0x01, 0x05, 0x03 };
+
+    if (r == g && g == b) {
+        unsigned char i = 0;
+
+        while (gray_brightness[i] < r) {
+            i++;
+        }
+
+        color_id = gray_colors[i];
+    } else if (half_color) {
+        color_id = term_colors[half_color - 1];
+    } else {
+        r = ((r << 2) + r) / 255;
+        g = ((g << 2) + g) / 255;
+        b = ((b << 2) + b) / 255;
+        color_id = 16 + ((r << 5) + (r << 2)) + ((g << 2) + (g << 1)) + b;
+    }
+
+    return color_id;
+}