function drawImage(imageObj) {
      var canvas = document.getElementById('myCanvas');
      var context = canvas.getContext('2d');
      var imageX = 10;
      var imageY = 6;
      imageWidth = imageObj.width;
      imageHeight = imageObj.height;

      context.drawImage(imageObj, imageX, imageY);

      var imageData = context.getImageData(imageX, imageY, imageWidth, imageHeight);
      data = imageData.data;
      console.log(imageData);

      // iterate over all pixels
      for(var i = 0, n = data.length; i < n; i += 4) {
      console.log("long du tableau : "+data.length);
        var red = data[i];
        var green = data[i + 1];
        var blue = data[i + 2];
        var alpha = data[i + 3];
          console.log(data[10]);
      }
        
      // iterate over all pixels based on x and y coordinates
      for(var y = 0; y < imageHeight; y++) {
  
        // loop through each column
        for(var x = 0; x < imageWidth; x++) {
            
          var red = data[((imageWidth * y) + x) * 4];
          var green = data[((imageWidth * y) + x) * 4 + 1];
          var blue = data[((imageWidth * y) + x) * 4 + 2];
          var alpha = data[((imageWidth * y) + x) * 4 + 3];
          console.log('rangée '+y+', colonne '+x+': RGBA = ('+red+','+green+','+blue+','+alpha+')');
        }
      }
    }