JSFiddle - React, Tailwind, and code Playground

by loktar

HTML

<h1>Click canvas below to remove blue.<h1>
<canvas id="canvas"></canvas>

JavaScript

var canvas = document.getElementById("canvas"),
    ctx = canvas.getContext("2d");

canvas.width = canvas.height = 256;

var colors = ['255,0,0', '0,255,0', '100,100,100', '0,0,255'];

for(var i = 0; i < 40; i++){
    ctx.fillStyle = 'rgb(' + colors[Math.floor(Math.random()*4)] + ')';
    ctx.fillRect(Math.random()*200, Math.random()*200, Math.random()*50, Math.random()*50);
}

var selectColor = [0,0,255];

canvas.onclick = function(){removeColor(selectColor);}

function removeColor(color){
    var canvasData = ctx.getImageData(0, 0, 256, 256),
        pix = canvasData.data;
    
    for (var i = 0, n = pix.length; i <n; i += 4) {
        if(pix[i] === color[0] && pix[i+1] === color[1] && pix[i+2] === color[2]){
             pix[i+3] = 0;   
        }
    }
    
    ctx.putImageData(canvasData, 0, 0);
}