64 lines
2.0 KiB
JavaScript
64 lines
2.0 KiB
JavaScript
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#!/usr/bin/env node
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// img-to-ascii.mjs — Convert a PNG/JPG image to ASCII text.
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//
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// Usage:
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// node img-to-ascii.mjs <image> [--cols 120] [--invert] [--ramp " .:-=+*#%@"]
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//
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// Dependency: sharp (npm i sharp). Sharp decodes PNG/JPG/WebP and resizes.
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//
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// Notes:
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// - Applies monospace cell-aspect correction (cells are ~2x taller than wide),
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// so rows = cols * (imgH/imgW) * 0.5.
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// - Luminance uses sRGB perceptual weights (0.2126/0.7152/0.0722).
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import sharp from 'sharp';
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function parseArgs(argv) {
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const args = { cols: 120, invert: false, ramp: ' .:-=+*#%@', file: null };
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for (let i = 2; i < argv.length; i++) {
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const a = argv[i];
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if (a === '--cols') args.cols = parseInt(argv[++i], 10);
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else if (a === '--invert') args.invert = true;
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else if (a === '--ramp') args.ramp = argv[++i];
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else if (!a.startsWith('--')) args.file = a;
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}
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return args;
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}
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async function main() {
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const { cols, invert, ramp, file } = parseArgs(process.argv);
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if (!file) {
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console.error('Usage: node img-to-ascii.mjs <image> [--cols N] [--invert] [--ramp "..."]');
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process.exit(1);
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}
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const CELL_ASPECT = 0.5; // monospace width:height
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const meta = await sharp(file).metadata();
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const rows = Math.max(1, Math.round(cols * (meta.height / meta.width) * CELL_ASPECT));
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// Resize to the character grid, drop alpha, get raw RGB bytes.
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const { data } = await sharp(file)
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.resize(cols, rows, { fit: 'fill' })
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.removeAlpha()
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.raw()
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.toBuffer({ resolveWithObject: true });
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const last = ramp.length - 1;
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const lines = [];
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for (let y = 0; y < rows; y++) {
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let line = '';
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for (let x = 0; x < cols; x++) {
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const i = (y * cols + x) * 3;
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let lum = (0.2126 * data[i] + 0.7152 * data[i + 1] + 0.0722 * data[i + 2]) / 255;
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if (invert) lum = 1 - lum;
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line += ramp[Math.round(lum * last)];
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}
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lines.push(line);
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}
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process.stdout.write(lines.join('\n') + '\n');
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}
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main().catch((err) => {
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console.error('Error:', err.message);
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process.exit(1);
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});
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