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ascii rendering of a canvas
// works great on about:dino
// 1. save this file to your snippets.
// 2. load about:dino
// 3. evaluate the snippet
// 4. hit up arrow to trigger the game.
// 5. profit
(function() {
perfnow = performance.now;
// slow down performance.now so the dino game is Slooooooooww
performance.now = (...args) => perfnow.call(performance) / 2.5;
window.outascii = window.outascii || document.createElement('textarea');
outascii.style.cssText = `
position: absolute;
top: 0px;
font-size: 8px;
width: 760px;
height: 363px;
z-index: 10;
font-family: monospace;
background: #000000e0;
color: #0bff0b;
right: 0;
`;
document.body.append(outascii);
let prevFrame = '';
const sourceCanvas = document.querySelector('canvas');
const backingCanvas = document.createElement('canvas');
const backcontext = backingCanvas.getContext('2d');
const scalingFactor = 6; // bigger is smaller.
const refreshRateInMs = 175;
// string length of 13 is expected below.
const ascii = '@GLftli;:,. '
.split()
.reverse()
.join('');
// might want to defer the first call to DCL or something..
render(sourceCanvas, backcontext, sourceCanvas.offsetWidth / 4, sourceCanvas.offsetHeight / 4);
function render(sourceCanvas, backcontext, w, h) {
// Draw source canvas onto the smaller backing canvas
backcontext.fillStyle = 'white';
backcontext.fillRect(0, 0, w, h);
backcontext.drawImage(sourceCanvas, 0, 0, w, h);
// Grab the pixel data from the backing canvas
var data = backcontext.getImageData(0, 0, w, h).data;
var chars = '',
px = 0,
pxlen = w * h * 4;
// Loop through the pixels
for (var ih = 0; ih < h; ih++) {
for (var iw = 0; iw < w; iw++) {
// Convert the color into an appropriate character based on luminance
// magic numbers depend on ascii string length of 13, so scale accordingly
chars += ascii[(62 * data[px++] + 123 * data[px++] + 23 * data[px++]) >>> 12];
px++; // don't need alpha
}
chars += '\n';
}
frame = `/*
${chars}
*/
//# sourceURL=foo.js`;
if (prevFrame !== frame) {
prevFrame = frame;
eval(frame);
}
// Write the char data into the output divs
outascii.textContent = chars;
// Start over!
setTimeout(_ => {
render(sourceCanvas, backcontext, w, h);
}, refreshRateInMs);
}
})();
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