JSFiddle - React, Tailwind, and code Playground

by farhatdz

HTML

<canvas id="myCanvas" width="6029" height="6968"></canvas>

JavaScript

var canvas = document.getElementById('myCanvas'); //get canvas from html code via identity

      var context = canvas.getContext('2d');    //get context of canvas
      var imageObj = new Image();       //create image object 
      imageObj.src = 'gauteng.png'; //define the image of the image object


      imageObj.onload = function()  //trigger function after the image has loaded in image object
      {
        try
        {
          context.drawImage(imageObj,0,0);  //draw the image object onto context of canvas

          var imgd = context.getImageData(3200,3200,1,1);   //get pixel at x coord 3200, and y coord 3200
          var pix = imgd.data;  //get the RGB values from pixel

          // print out RGB values with alert            
          alert('R val= '+pix[0].toString()+ "\r\nG val= "+pix[1].toString()+"\r\nB val= "+pix[2].toString());

        }
        catch(err)  //display error message if exception is thrown
        {
          alert(err.toString());
        }
     };
     
     
     imageObj.onload = function() {

    try
    {
        var inputFile = new XMLHttpRequest(); 
        inputFile.open('get', 'gauteng.png', true); //open example file

        inputFile.onreadystatechange = function()
        {
            if(inputFile.readyState==4) //document is ready to parse
            {
                context.drawImage(imageObj, 0, 0);

                //pixel location from image
                var imgd = context.getImageData(3200,3200,6029,6968);
                var pix = imgd.data;

                alert(pix[0].toString()+ " "+pix[1].toString()+" "+pix[2].toString());
            }
        }

        inputFile.send(null); //close file after finished

    }
    catch(err){ alert(err.toString());}
  };