Canvas

Drawing

by Boban Stojanovski

HTML

<body>
HELLO  <canvas id="canvas" width="500" height="500"></canvas>
</body>

CSS

body {
  background-color: gray
}

JavaScript

var canvas = document.getElementById('canvas'),
  ctx = canvas.getContext('2d'),
  rect = {},
  drag = false;

function init() {
  canvas.addEventListener('mousedown', mouseDown, false);
  canvas.addEventListener('mouseup', mouseUp, false);
  //canvas.addEventListener('mousemove', mouseMove, false);
}

function mouseDown(e) {
  rect.startX = e.pageX - this.offsetLeft;
  rect.startY = e.pageY - this.offsetTop;
  drag = true;
}

function mouseMove(e) {
  if (drag) {
    rect.w = (e.pageX - this.offsetLeft) - rect.startX;
    rect.h = (e.pageY - this.offsetTop) - rect.startY ;
    ctx.clearRect(0,0,canvas.width,canvas.height);
    drawRect();
  }
}

function mouseUp(e) {
  rect.w = (e.pageX - this.offsetLeft) - rect.startX;
    rect.h = (e.pageY - this.offsetTop) - rect.startY ;
  drawRect();
  drag = false;
  
  console.log(rect);
}

function drawRect() {
  //ctx.fillRect(rect.startX, rect.startY, rect.w, rect.h);
  
  ctx.rect(rect.startX, rect.startY, rect.w, rect.h);
   ctx.stroke();
}

init();