Accessing vector features by clicking in close proximity to, but not directly on, a vector in OpenLayers

Question

Accessing vector features by clicking in close proximity to, but not directly on, a vector in OpenLayers

I'm working with an Open Street Map that includes vectors (lines) displaying on the roads. Currently, I can only retrieve information about a vector by clicking directly on its pixels. Is there a way to make it so that I can click near the vector (a few pixels off) and still get the relevant information, in order to be less precise?

Code:

Here is the code snippet I am using to get features when I click on a vector:

var displayFeatureInfo  = function (pixel, coordinate) {
            var features = [];
            map.forEachFeatureAtPixel(pixel, function (feature, layer) {
                features.push(feature); // Storing each feature found in an array
            });

            if (features.length > 0) {   // If there are one or more features
                $("#popup").html('<object data=' + "http://URLToLoadDataFrom '/>'); // Loading data via jQuery
                popup.setPositioning('top-left');
                popup.setPosition(coordinate);
                container.style.display = 'block';
            } else {
                container.style.display = 'none';
            }                          

        };

        map.on('click', function (evt) {
            var coordinate = evt.coordinate;
            displayFeatureInfo(evt.pixel, coordinate);    
        });

Thanks for any help in advance.

javascript openlayers openlayers-3

Answer 1

Answer №1

You have the option to create an extent using the provided pixel and base your feature selection on the extent rather than a single point. This means utilizing the

vector.getSource().forEachFeatureIntersectingExtent

method instead of map.forEachFeatureAtPixel.

Take a look at this (sample here):

var displayFeatureInfo  = function (pixel, coordinate) {
            var features = [];
            //adjust this offset in pixels as needed
            var pixelOffSet = 5; 
            var pixelWithOffsetMin = [pixel[0]-pixelOffSet,pixel[1]+pixelOffSet];
            var pixelWithOffsetMax = [pixel[0]+pixelOffSet,pixel[1]-pixelOffSet];
            var XYMin =map.getCoordinateFromPixel(pixelWithOffsetMin)
            var XYMax =map.getCoordinateFromPixel(pixelWithOffsetMax)
            var extent = XYMax.concat(XYMin);
            var extentFeat= new ol.Feature(new ol.geom.Polygon([[
            [extent[0],extent[1]],
            [extent[0],extent[3]],
            [extent[2],extent[3]],
            [extent[2],extent[1]],
            [extent[0],extent[1]]
            ]]));   

            vector.getSource().forEachFeatureIntersectingExtent(extentFeat.getGeometry().getExtent(), 
            function (feature) {
                features.push(feature); // Adds each found feature to the array
            });

            if (features.length > 0) {   // If there are one or more features
                console.log("Features found when clicked on offset",features)
               // container.style.display = 'block';
            } else {
              console.log("No features found when clicking on offset")
            }                          

        };

        map.on('click', function (evt) {
            var coordinate = evt.coordinate;
            displayFeatureInfo(evt.pixel, coordinate);    
        });

Answer 2

You have the option to create an extent using the provided pixel and base your feature selection on the extent rather than a single point. This means utilizing the

vector.getSource().forEachFeatureIntersectingExtent

method instead of map.forEachFeatureAtPixel.

Take a look at this (sample here):

var displayFeatureInfo  = function (pixel, coordinate) {
            var features = [];
            //adjust this offset in pixels as needed
            var pixelOffSet = 5; 
            var pixelWithOffsetMin = [pixel[0]-pixelOffSet,pixel[1]+pixelOffSet];
            var pixelWithOffsetMax = [pixel[0]+pixelOffSet,pixel[1]-pixelOffSet];
            var XYMin =map.getCoordinateFromPixel(pixelWithOffsetMin)
            var XYMax =map.getCoordinateFromPixel(pixelWithOffsetMax)
            var extent = XYMax.concat(XYMin);
            var extentFeat= new ol.Feature(new ol.geom.Polygon([[
            [extent[0],extent[1]],
            [extent[0],extent[3]],
            [extent[2],extent[3]],
            [extent[2],extent[1]],
            [extent[0],extent[1]]
            ]]));   

            vector.getSource().forEachFeatureIntersectingExtent(extentFeat.getGeometry().getExtent(), 
            function (feature) {
                features.push(feature); // Adds each found feature to the array
            });

            if (features.length > 0) {   // If there are one or more features
                console.log("Features found when clicked on offset",features)
               // container.style.display = 'block';
            } else {
              console.log("No features found when clicking on offset")
            }                          

        };

        map.on('click', function (evt) {
            var coordinate = evt.coordinate;
            displayFeatureInfo(evt.pixel, coordinate);    
        });

Accessing vector features by clicking in close proximity to, but not directly on, a vector in OpenLayers

Code:

Answer №1

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