H E L L O V I S I T E R !!!
This useful app is coded with Pure Javascipt, CSS and HTML.
You can see these codes in script.js :
for (let i = 0; i < data.length; i += 4) { const grey = data[i] * 0.21 + data[i + 1] * 0.71 + data[i + 2] * 0.07; data[i] = grey + 95; data[i + 1] = grey + 58; data[i + 2] = grey; }
This for loop means data changes every 4 pixels that you can find with console.log for all data(pixels). **I assume that you already know "the picture consists of lots of pixels.