function changeZoom (layer, direction, cursorLocation) {
    var oldWidth = canvasSize[0] * zoom;
    var oldHeight = canvasSize[1] * zoom;
    var newWidth, newHeight;

    //change zoom level
    //if you want to zoom out, and the zoom isnt already at the smallest level
    if (direction == 'out' && zoom > 1) {
        zoom -= Math.ceil(zoom / 10);
        newWidth = canvasSize[0] * zoom;
        newHeight = canvasSize[1] * zoom;

        //adjust canvas position
        setCanvasOffset(layer.canvas, layer.canvas.offsetLeft + (oldWidth - newWidth) *cursorLocation[0]/oldWidth, layer.canvas.offsetTop + (oldHeight - newHeight) *cursorLocation[1]/oldWidth);
    } else if (direction == 'in' && zoom + Math.ceil(zoom/10) < window.innerHeight/4){
    //if you want to zoom in 
        zoom += Math.ceil(zoom/10);
        newWidth = canvasSize[0] * zoom;
        newHeight = canvasSize[1] * zoom;

        //adjust canvas position
        setCanvasOffset(layer.canvas, layer.canvas.offsetLeft - Math.round((newWidth - oldWidth)*cursorLocation[0]/oldWidth), layer.canvas.offsetTop - Math.round((newHeight - oldHeight)*cursorLocation[1]/oldHeight));
    }

    //resize canvas
    layer.resize();

    // adjust brush size
    updateCursor();
}