How to get the RGB data from an area of image with JavaScript

I cant get the RGB data from an image, what I am doing is to get de x, y, width and height of an area, so, I want to know the RGB data from the area, no of a pixel, of the AREA.

I was trying to use a canvas with getImageData, but it returns just a pixel, Im using a library to get the parameters of the x,y,w and h, my image size is the same of my canvas

This is what Im doing

const canvas2 = document.getElementById('canvasIMG'); //Get the canvas
const img2 = document.getElementById('imagen');//Get the image
const ctxImagen = canvas2.getContext('2d');//Get the context of canvas
ctxImagen.drawImage(img, 0, 0);
var rgb = ctxImagen.getImageData(ejex,ejey,1000, 1000).data; //"ejex" is the x coordinate and "ejey" is y coordinate, and 1000 is the width and the height, i tried to change the values of w and h, and is the same always, I download a RGB image, and in the console just print the color of both uppset corners
console.log("red ", rgb[0]);
console.log("green ", rgb[1]);
console.log("blue ", rgb[2]);
console.log("alpha ", rgb[3]);

I dont receive any error messages.