检查HTML5 Canvas上的像素是否为黑色

Question

I'm trying to find if a pixel is black or not on a canvas

    var check = function(player,keyPressed) {
//series of ifs to determine what pixel to check. 
    }

I would need to return either true or false if the pixel is false, I've tried getImageData but I wasn't able to figure out how to use it properly.

Answer 1

var canvas= document.getElementById('myCanv');
var pixelData = canvas.getContext('2d').getImageData(event.clientX, event.clientY, 1, 1).data;

That is it !!

Of course, Assuming that , you have :

   <canvas id="myCanv"></canvas> 

FIDDLE

Then :

function isBlack(dataPixel){
   if(dataPixel[0]==dataPixel[1] && dataPixel[1]==dataPixel[2] && dataPixel[2]===0 ){
      return true
   }
}

http://jsfiddle.net/abdennour/4kdLfooj/11/