Question

I have this piece of code that runs a function to transform a color image with the class=”gray” to gray scale.

$(document).ready(function(){
  $('.gray').click(function(){
    this.src = grayscale(this.src);
  });
});

function grayscale(img){        
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');

var imgObj = new Image();
imgObj.src = img;

canvas.width = imgObj.width;
canvas.height = imgObj.height; 

ctx.drawImage(imgObj, 0, 0); 

var imgPixels = ctx.getImageData(0, 0, canvas.width, canvas.height);

for(var y = 0; y < imgPixels.height; y++){
        for(var x = 0; x < imgPixels.width; x++){
           var i = (y * 4) * imgPixels.width + x * 4;
           var avg = (imgPixels.data[i] + 
                      imgPixels.data[i + 1] + 
                      imgPixels.data[i + 2]
                      ) / 3;
           imgPixels.data[i] = avg; 
           imgPixels.data[i + 1] = avg; 
           imgPixels.data[i + 2] = avg;
        }
}

ctx.putImageData(imgPixels, 0, 0, 0, 0, imgPixels.width, imgPixels.height);
return canvas.toDataURL();
}

This works OK with the click function, but I want that color image to become gray scaled immediately right after the page is loaded, so the function must run without the click. How to do this?

Answer 1

You can substitute click with each.