I have some geoJSON polygons that I render via layers on top of my map. Depending on the shape itself and the zoom level, sometimes the rendered shapes are too small and it doesn't make sense to even show them.
Is there a way to hide shapes that have rendered area less than some number?
So, as Babis.amas suggested, first I calculate the area of the feature with help of turf.area. It gives the value in square meters. Then I convert this value to pixels using the function mentioned here. And then it really depends on the shape type I'm dealing with. If the shape considered to be too small to be rendered, I just don't add it to the layer data feature collection.
Related
I’m attempting to create a seating diagram using React Leaflet 2.7.0. I’ve made the coordinates relative to the Map bounds by setting the crs property to L.CRS.Simple.
I know how to create and place vector circles by manually inputting coordinates to represent a seat. This method allows the shapes to scale proportionately when zoomed (rather than using Markers, which don’t scale). My challenge is finding a way to efficiently determine coordinates based on an image of a seating chart.
I’m wondering if anyone knows of a way to extract coordinates based on an image to say a geoJson or Javascript object; Perhaps a plugin or other third-party, or built-in Leaflet feature I’m not aware of.
The image shows the concept of what I’m trying to achieve.
desired concept:
what I normally do is, create an event that when onclick it would gather the coordinates related to the image and after that push it to an array which after I finish I can console log the array which I just copy-paste to my text editor
Using geojson.io page I want to draw some districts/countries.
I'm drawing each district separately as there is no multipolygons in Leaflet Draw. However when I'm drawing the borders even with maximum zoom - the borders will never be exactly the same. Coordinates will differ to some extend which is natural. Hence when I am downloading the data in topojson , the data are not valid to display meshes between different districts
How to achieve the goal to have the borders always with the same coordinates?
For example it could be achieved by having the markers visible during drawing and just picking up the one I'm interested in(on a same border) by mouse click - the same way the shape is finished.
I have downloaded the source code, read it (it is nice), searched through docs and thinking how to adjust it for my goal but I'm lost :/
Leaflet.Snap did the trick.
I was afraid that snapping will be not exact for the borders but it is :)
I'm using leaflet to create a proportional symbol map. Without boring you with the code, I'm wondering if there is a way to draw smaller symbols on top of bigger ones. There doesn't seem to be any set order to my current symbols, so bigger circles sometimes obscure the smaller ones.
Just to clarify: I'm trying to re-arrange smaller circles on top of big ones and they are in the same layer.
Can someone point me in the right direction here? Thanks!
If your "symbols" / circles are individual vector shapes (typically L.circle), then you can use bringToFront() and bringToBack() methods to change their relative order.
I am working on trying to create a basic, grid-based, but performant weather-arrow visualization system.
EDIT 2:
Up-to-date version here: ( Mapbox Tracker ) of the system using the workflow which is described below
Usage Instructions:
- Click on Wind icon (on the left)
- Wait for triangles to occupy screen
- Pan time-slider (at the bottom)
As you will observe (especially on larger resolutions or when panning time slider quickly) there is quite a performance hit when drawing the triangles.
I would greatly appreciate any advice on where to start with either using something in the current API which would help, or any ideas on how to tap into the current graphics pipeline with some type of custom buffer where I would only need to rotate, scale, change color of triangles already populated in screen space.
I feel as though my specific use-case would greatly benefit from something like this, I really just don't know how to approach it.
I have a naive implementation running using this workflow:
Create a geojson FeatureCollection source
Create a fill layer
Using Data Driven property: fill-color
Data function:
Get map bounds
Project sw & ne into screen points (map.project(LatLng))
Divide height and width into portions
Loop through width and height portions
Lookup data
Access data rotation property
Create vertices based on center point + size
Rotate vertices
Create Point objects for vertices
Unproject Point Object and wrap map.unproject(Point).wrap()
Create Feature Object, assign Data driven Color
Assign unprojected LatLng as Coordinates to Polygon geometry
Add to Feature Array for Collection
Call setData on layer
So while this works, I'm looking for advice for a more performance friendly approach.
What I'm thinking here is whether I can somehow create a custom layer, one where I only need to draw to screen co-ordinates to represent the data relative to its LatLng point. So that I can draw colored, scaled, rotated triangles in screen space, and then have them update to relevant data from the new relative LatLng position.
E.g. Update some type of Mesh on screen instead of having to: unproject, then update feature collection source using map.getSource('arrows').setData(d), requestAnimationFrame(function) etc.
I've done similar in three.js in other projects but I would much rather use something that is more mapbox native. Does this sound feasible? Am I going to see a decent performance boost if so?
I've not dealt with raw gl calls before etc so I might need a pointer or two in the right direction if its going to need to get as low level as that.
EDIT:
Previous Implementation using gmaps / three.js : volvooceanrace
(wait for button on left to go from grey to black) click on top button which shows a 'wind' label when hovered over, slide red time bar underneath to change data.
Added screenshot of current working implementation
Mapbox GL Arrows
Not sure what was available in 2016, but a reasonable approach these days might be to use symbol layers, and the icon-rotate data-driven property to rotate each icon based on the property of its data point.
I am currently trying to create a blue, circular, pie-chart-esque image for my website. The circle will be split into 6 different segments.
What I want to happen is that when the user hovers over a particular segment, this segment will turn orange, and some text will appear beside the circle corresponding to that segment.
I have found some resources online which achieve nearly the effect I need using CSS image maps. http://www.noobcube.com/tutorials/html-css/css-image-maps-a-beginners-guide-/ However, these techniques split up an image using rectangles. If I were splitting up a circular object I would prefer to split up the area based on particular arcs.
I assume this is beyond the reach of pure HTML and CSS. I do not have a great deal of experience with web languages, although I have had passing experience with JQuery. What are the techniques I need to solve my problem and what technology would be best to implement it?
you can create image maps that are not rectangular, but use polygon shapes.
this useful tool http://www.image-maps.com/ will let you achieve what you are looking for, without having to write your own polygon mapping!
A few options:
HTML image map
It's simple to create an HTML image map that comes very close to the shape of each slice of the circle, but there are limitations to HTML images maps. For instance, you can't nest content inside each slice of the image map (as an easy way to implement a hover pop-up). If an HTML image map is adequate for you, it's the simplest solution.
CSS image map
To define circle-slice shapes, a CSS image map is impractical, unless you only need a very-rough approximation of the hotspots for each circle slice. But if you could live with that, you'd have a lot more flexibility as far as the functionality.
onmousemove
You could also get the mouse coordinates with an onmousemove event handler for the entire circle, and then do your own calculations to determine which circle slice the mouse is in. This allows you to accurately define the hotspots for each circle slice, and you'd have more flexibility than with an HTML image map. But the calculations may take a little work.
I have a solution for this using mainly HTML and CSS with a tiny bit of jQuery to handle the showing of the text by the side of the circle.
It does however use some CSS properties that are not very widely supported such as pointer-events
JSFiddle Demo