How to create a color picker in html?

Question

How to make a color picker, like we see in different websites where users can scroll down different colors and on click can get the color code?

I have tried of maki

Answer 1

In addition for answer of Gil Epshtain, if you do not wanna load an image you can fill the canvas with gradients

function initColorPicker() {
  var canvas = document.getElementById('colorCanvas');
  var canvasContext = canvas.getContext('2d');

  let gradient = canvas.getContext('2d').createLinearGradient(0, 0, canvas.width, 0)
  gradient.addColorStop(0, '#ff0000')
  gradient.addColorStop(1 / 6, '#ffff00')
  gradient.addColorStop((1 / 6) * 2, '#00ff00')
  gradient.addColorStop((1 / 6) * 3, '#00ffff')
  gradient.addColorStop((1 / 6) * 4, '#0000ff')
  gradient.addColorStop((1 / 6) * 5, '#ff00ff')
  gradient.addColorStop(1, '#ff0000')
  canvas.getContext('2d').fillStyle = gradient
  canvas.getContext('2d').fillRect(0, 0, canvas.width, canvas.height)

  gradient = canvas.getContext('2d').createLinearGradient(0, 0, 0, canvas.height)
  gradient.addColorStop(0, 'rgba(255, 255, 255, 1)')
  gradient.addColorStop(0.5, 'rgba(255, 255, 255, 0)')
  gradient.addColorStop(1, 'rgba(255, 255, 255, 0)')
  canvas.getContext('2d').fillStyle = gradient
  canvas.getContext('2d').fillRect(0, 0, canvas.width, canvas.height)

  gradient = canvas.getContext('2d').createLinearGradient(0, 0, 0, canvas.height)
  gradient.addColorStop(0, 'rgba(0, 0, 0, 0)')
  gradient.addColorStop(0.5, 'rgba(0, 0, 0, 0)')
  gradient.addColorStop(1, 'rgba(0, 0, 0, 1)')
  canvas.getContext('2d').fillStyle = gradient
  canvas.getContext('2d').fillRect(0, 0, canvas.width, canvas.height)


  canvas.onclick = function(e) {
  	console.log()
    var imgData = canvasContext.getImageData((e.offsetX / canvas.clientWidth) * canvas.width, (e.offsetY / canvas.clientHeight) * canvas.height, 1, 1)
    var rgba = imgData.data;
    var color = "rgba(" + rgba[0] + ", " + rgba[1] + ", " + rgba[2] + ", " + rgba[3] + ")";
    console.log("%c" + color, "color:" + color)
  }
}

initColorPicker()

* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

html {
  height: 100%;
  width: 100%;
}

body {
  height: 100%;
  width: 100%;
  margin: 0;
}

canvas {
  height: 100%;
  width: 100%;
}