var fileInput = document.getElementById('fileInput');

 
    fileInput.addEventListener('change', function() {
    var file = fileInput.files[0];

    var img = new Image();
    img.onload = function() {
    ctx_image.drawImage(img, 0, 0, ctx_image.canvas.width, ctx_image.canvas.height);
    m_tex.update_canvas_ctx(imagePlane, "CubeTexture");
    }
    img.src = URL.createObjectURL(file);
    });

onresize = function()
{
    var bodyWidth  = document.body.clientWidth
      , bodyHeight = document.body.clientHeight;
    var scalable = document.getElementById("main_canvas_container");
    scale = Math.min(bodyWidth / 1920, bodyHeight / 1080);
    
    scalable.style.top = (bodyHeight - (scalable.offsetHeight * scale)) / 2 + "px";
    scalable.style.left = (bodyWidth - (scalable.offsetWidth * scale)) / 2 + "px";
    scalable.style.webkitTransform = "scale(" + scale + ")";
}

onresize();