functions.js

var labelEngine = new labelgun["default"](
    function(label){
        label.labelObject.hide = true;
    }, 
    function(label){
        label.labelObject.hide = false;
    }
);

var createTextStyle = function(feature, resolution, labelText, labelFont,
                               labelFill) {

    if (feature.hide) {
        return new ol.style.Text(); 
    } 

    var textStyle = new ol.style.Text({
        font: labelFont,
        text: labelText,
        textBaseline: "middle",
        textAlign: "left",
        offsetX: 8,
        offsetY: 3,
        fill: new ol.style.Fill({
          color: labelFill
        })
    });

    return textStyle;
};

function stripe(stripeWidth, gapWidth, angle, color) {
    var canvas = document.createElement('canvas');
    var context = canvas.getContext('2d');
    canvas.width = screen.width;
    canvas.height = stripeWidth + gapWidth;
    context.fillStyle = color;
    context.lineWidth = stripeWidth;
    context.fillRect(0, 0, canvas.width, stripeWidth);
    innerPattern = context.createPattern(canvas, 'repeat');

    var outerCanvas = document.createElement('canvas');
    var outerContext = outerCanvas.getContext('2d');
    outerCanvas.width = screen.width;
    outerCanvas.height = screen.height;
    outerContext.rotate((Math.PI / 180) * angle);
    outerContext.translate(-(screen.width/2), -(screen.height/2));
    outerContext.fillStyle = innerPattern;
    outerContext.fillRect(0,0,screen.width,screen.height);

    return outerContext.createPattern(outerCanvas, 'no-repeat');
};