I'm using OpenLayers 3 and OpenStreetMap to print maps on paper, and for this I'd need to render the maps with more details and higher DPI than are shown on the screen. I'm using CSS to set the size of ol.Map's target in centimeters to the desired size for the printout (.map { width: 7cm; height: 6.3cm; }).
By default OpenLayers shows one of my maps like this, which is too low detail for my needs:
By changing the map size with map.setSize(map.getSize().map(function (x) { return x*2; })); I'm able to increase the detail closer to what I need:
But the problem with this hack is that when the window is resized, the size is reset and it will look wrong like this:
How would I be able to control the OSM zoom level and map DPI independently of the map's size on screen to achieve the desired outcome (the second picture) reliably?
A solution I've found is to put the map inside two nested divs. The inner one has, for example, width: 200%; height: 200%, and the outer one would have transform: scale(.5) translate(-50%,-50%);. This would double the resolution the user sees.
This approach changes the pixel zoom level relative to the zoom level on screen. However, it needs to be recalculated and updated whenever the user zooms the map.
Related
Given any screen resolution, is there a way that I can figure out the amount of points in an inch? For instance, if I wanted to create an NSView that was 8.5 inches by 11 inches (like a sheet of a paper), is there an algorithm that will allow me to obtain the correct point values for the frame across many different types of Macs and screen resolutions?
It's not straightforward. I'm not sure there's a good way. I can provide an approach, but I haven't confirmed that this works reliably:
First, you can use CGDisplayScreenSize() to get the screen's physical size in millimeters. You can obtain the CGDirectDisplayID for a screen from NSScreen, which you can, in turn, get from the window. Obtain the screen's deviceDescription and get the value for the "NSScreenNumber" key. That may need to be cast to CGDirectDisplayID.
The problem from there is that the display mode may not fill the screen. It could be letterboxed or pillarboxed. Or, it might be stretched. This should be fairly uncommon these days, but still possible. You can obtain the display mode using CGDisplayCopyDisplayMode(). To determine if it's stretched, you can examine its ioFlags to see if they contain the bitmask kDisplayModeStretchedFlag (declared in IOKit).
If it's stretched, the screen's frame will have to be mapped to its size in millimeters separately for the X and Y axes. You assume the screen's frame.width (in points) maps to the full physical width, and similarly for the height.
If the mode is not stretched, you'll have to check the aspect ratio of the frame and the screen physical size to see if it's letter- or pillarboxed. If the aspect ratios are very close, then it's presumably not. That case is similar to the stretched case, but the width and height mappings should be equivalent.
If the aspect ratios differ significantly, then you compare them. If the screen's physical aspect ratio is larger than the frame's, then the screen is physically wider than the mode is using (pillarboxed). So, you compute the mapping from points to millimeters from the two heights. If the physical aspect ratio is smaller than the logical one, then the mode is letterboxed and you use the widths to compute the mapping.
I am building a map and want to use the leaflet markercluster plugin to cluster any markers that intersect visibly (the icons overlap each other). I can't seem to figure out a way to check whether the markers icons intersect though.
I've examined the documentation and the Marker objects. The marker object has no "bounds" object and has no function to return the bounds of the icon.
Yes, it's possible.
This is implemented in some Leaflet plugins, like Leaflet.LayerGroup.Collision - the technique involves fetching the computed style of each icon's HTML element to get the actual size in CSS pixels, offset those numbers by the relative pixel position of the marker's LatLng, and using a rtree data structure to speed up the calculation of the overlaps. Do have a look at the complete source for LayerGroup.Collision plugin.
Note that this technique only takes into account the rectangular bounding boxes of the icons; while it would be possible to check for the individual transparent pixels, that would involve more complex data structures and a different technique to fetch the opacity of each pixel.
(pretty new to Mapbox and JS, so I'm in a bit over my head)
I'm working on a page where the user needs to adjust the size of map container. It needs to be able to get accurate bounds and center point of the resized map (via map.getBounds and map.getCenter).
When I use JS to adjust the size of the container div, the center and bounds are not adjusted.
Fiddle: http://jsfiddle.net/xcow63sm/3/
Panning/zooming results in updated center and bounds. Browser window resize (if you have width or height set to 100%) works too. I would expect changing the container dimensions would adjust center and bounds.
However, if you use the form fields to adjust the height/width of the container div, the center and bounds do not. I've tried (with increasing desperation):
function resize (){
var inputwidth = document.getElementsByName("mapwidth")[0].value;
var inputheight = document.getElementsByName("mapheight")[0].value;
var mapDiv = document.getElementById('map');
var mapcenter = map.getCenter();
mapDiv.style.width = inputwidth;
mapDiv.style.height = inputheight;
map.updateSize();
map.update();
map.resize();
map.invalidateSize();
document.getElementById("mapcenter").value = mapcenter;
Edit: this seems to apply but I can't make sense of it: Resizing a leaflet map on container resize
If I understand you, you have two issues: you don't like how the map is positioned after its size changes, and you're getting white space.
Map positioning after resize
There are at least three valid options for how a map should update if, say, its width and height are suddenly doubled:
keep the same northern and western bound, extend the eastern and southern bounds. (Expanding the viewing area right and down)
move all four bounds outwards (keeping the centre of the map in the same place)
leave all four bounds where they are are, but change the zoom, so the same geographic area is displayed, but in more detail.
I think your issue is that Mapbox is choosing option 1, but you want one of the other two options. The solution, as I think you've discovered, is simply to do your own maths and set the bounds how you want them.
Map failing to repaint correctly
Your second issue is that when you resize, calling map.resize() isn't updating the internal size of the map properly, and you're left with white space. The reason for this is you're using animated CSS properties. So when you do this:
mapDiv.style.width = inputwidth;
mapDiv.style.height = inputheight;
map.resize();
This doesn't work because the map's size hasn't actually transitioned to the new size yet. You can work around it like this:
mapDiv.style.width = inputwidth;
mapDiv.style.height = inputheight;
window.setTimeout(()=>map.resize(), 500);
There's probably a better event you can listen to, to keep updating as the map area expands.
Updated fiddle here: http://jsfiddle.net/xcow63sm/11/
Btw you should consult the documentation here. I'm not sure where you got map.updateSize() from but that's not Mapbox-GL-JS :)
I'm trying to set the fitBounds option in a leaflet map like this:
var bounds = new L.LatLngBounds([[Math.max(lat, borneLat), Math.max(lng, borneLng)], [Math.min(lat, borneLat), Math.min(lng, borneLng)]]);
map.fitBounds(bounds, { padding: [20, 20] });
However this doesn't seem to add any padding ? at least the map "zoom level" doesn't change, and it's always showing the two points in the edges (i.e. one is top far right and the other is bottom far left). For some marker sets, it works ok, the zoom is at a decent level away and you can see everything nicely. However when the items are quite close to each other, it seems it zooms in a bit too much unless I can fit it with some "padding."
Also I'm unsure if the bounds would be correct like that? Should I use instead just:
var bounds = [[Math.max(lat, borneLat), Math.max(lng, borneLng)], [Math.min(lat, borneLat), Math.min(lng, borneLng)]];
map.fitBounds(bounds, {padding: []}) should work. I suggest you to change padding to eg. [50, 50], maybe your padding values are too small.
Check out this JSFiddle example.
Leaflet only zooms between integer-value zoom levels by default. Past version 1.0.0, "fractional zooms" are available with the "zoomSnap" parameter:
var map = L.map('map', {
zoomSnap: 0.1
});
This will allow smaller padding values to be visible, but will also affect scrollWheelZoom behavior.
I came across this problem. As I understand the padding is controlled by the zoom. In my example all padding settings under 10 make no difference. As soon as the padding goes to 10 the map is zoomed out one level and there is padding. Furhter increasing the padding value has no influence, until it is so big that another zoom-out level is reached.
FWI, you can also set a max zoom level to the map like so:
var map = L.mapbox.map('map', 'mapbox.emerald', {
maxZoom: 16
});
this way you can avoid the map zooming in too much in case the markers are too close togther.
I am not talking about just resize the image,
I want to zoom in the price, then people focus on that price.
I want to do a resize action, then data will reload the specify area of the chart.
Similar as this application:
http://itunes.apple.com/us/app/chart-tool/id366727994?mt=8
You can zoom in by adjusting the plot ranges on the plot space. Reduce the length of the range to zoom in and increase it to zoom out. No need to reload the data unless you want to add more detail (== more data points) at the higher zoom level.