Javascript OpenLayers 中的最小/最大缩放级别
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Min/max zoom level in OpenLayers
提问by David Pfeffer
I'm using OpenLayers to display a map in a web page. I am using tiles from CloudMade, but the same issues occur with the Mapnik tiles from OpenStreetMap.
我正在使用 OpenLayers 在网页中显示地图。我使用的是来自 CloudMade 的图块，但是来自 OpenStreetMap 的 Mapnik 图块也出现了同样的问题。
I'm trying to restrict the map so that the user cannot zoom all the way out to world view -- I want them to stay at roughly a city level zoom at minimum.
我试图限制地图，以便用户无法一直放大到世界视图 - 我希望他们至少保持大致城市级别的缩放。
I have tried using the minZoomLevel/ maxZoomLevel/ numZoomLevelsproperties; only the maxZoomLeveland numZoomLevelsproperties seem to work, whereas the minZoomLevelproperty seems to be completely ignored.
我已经使用试图minZoomLevel/ maxZoomLevel/numZoomLevels性能; 只有maxZoomLevel和numZoomLevels属性似乎有效，而该minZoomLevel属性似乎完全被忽略。
Is there another way to accomplish this?
有没有另一种方法来实现这一点？
采纳答案by geographika
minZoomLevel is not supported for XYZ layers, of which OSM is a subclass.
XYZ 层不支持 minZoomLevel，其中 OSM 是其子类。
See the following tickets for workarounds:
有关变通方法，请参阅以下票证：
- http://trac.osgeo.org/openlayers/ticket/2909(apply a zoom offset)
- http://trac.osgeo.org/openlayers/ticket/2189(add minZoomLevel patch)
- http://trac.osgeo.org/openlayers/ticket/2909（应用缩放偏移）
- http://trac.osgeo.org/openlayers/ticket/2189（添加 minZoomLevel 补丁）
回答by Jonathan
You could override the isValidZoomLevelfunction. Something like this (not tested):
您可以覆盖该isValidZoomLevel功能。像这样的东西（未测试）：
OpenLayers.Map.isValidZoomLevel = function(zoomLevel) {
return ( (zoomLevel != null) &&
(zoomLevel >= 2) && // set min level here, could read from property
(zoomLevel < this.getNumZoomLevels()) );
}
EDIT
编辑
Or you would need to override the available resolutions, see the example here: http://dev.openlayers.org/examples/zoomLevels.html
或者您需要覆盖可用的分辨率，请参见此处的示例：http: //dev.openlayers.org/examples/zoomLevels.html
回答by Graham
I found the simplest way to restrict the maxZoom levels for a XYZ layer was to override the getNumZoomLevels method:
我发现限制 XYZ 层的 maxZoom 级别的最简单方法是覆盖 getNumZoomLevels 方法：
map.getNumZoomLevels = function(){
return 10;
};
This pevents zooming beyond level 10 and also draws the zoomBar control correctly. This and a combination of the zoomOffsetoption should allow you to easily control min/max zoom without having to mess around with resolutions or subclasses.
这可以防止缩放超过 10 级，并且还可以正确绘制 zoomBar 控件。这和zoomOffset选项的组合应该允许您轻松控制最小/最大缩放，而不必弄乱分辨率或子类。
回答by jjmontes
Other answers here refer to OpenLayers versions prior to version 3.
此处的其他答案是指版本 3 之前的 OpenLayers 版本。
With OpenLayers 3, you can use the maxZoommap option when initializing the map, as follows:
使用 OpenLayers 3，您可以maxZoom在初始化地图时使用地图选项，如下所示：
var map = new ol.Map({
target: 'mapcontainer-001',
layers: layers, // Layers need to be initialized previously
view: new ol.View({
center: ol.proj.transform([-5.12345, 42.12345], 'EPSG:4326', 'EPSG:3857'),
zoom: 12,
maxZoom: 19
})
});
More information can be found in OpenLayers documentation: http://openlayers.org/en/v3.0.0/doc/tutorials/concepts.html
更多信息可以在 OpenLayers 文档中找到：http: //openlayers.org/en/v3.0.0/doc/tutorials/concepts.html
回答by Fernando Sanchiz
Now i use this in the "View":
现在我在“视图”中使用它：
view: new ol.View({
center: ol.proj.transform([-3.707524, 40.485644], 'EPSG:4326',EPSG:3857'),
zoom: 15,
maxZoom: 17,
minZoom: 6
}),
And it works fine
它工作正常
回答by netbrain
I ended up with this solution as i could not figure out how to use zoomOffset in my setup.
我最终得到了这个解决方案，因为我无法弄清楚如何在我的设置中使用 zoomOffset。
map.getNumZoomLevels = function(){
return (options.maxzoom-options.minzoom+1);
};
map.isValidZoomLevel = function(zoomLevel) {
var valid = ( (zoomLevel != null) &&
(zoomLevel >= options.minzoom) &&
(zoomLevel <= options.maxzoom) );
if(!valid && map.getZoom() == 0){
map.zoomTo(options.maxzoom - (options.maxzoom - options.minzoom)/2);
}
return valid;
}
回答by Akna
I tried something like this and it works for me:
我试过这样的事情，它对我有用：
map.newMoveTo = map.moveTo;
map.moveTo = function(lonlat,zoom,options){
return(zoom>=maxZoom && zoom<=minZoom)?map.newMoveTo(lonlat,zoom,options):false;
};
回答by nachtigall
The best answer I found (including an example) was at OpenLayers - limit the number of zoom levels. I don't paste it here, please see the instructions over there.
我找到的最佳答案（包括一个示例）是在OpenLayers - limit the number of zoom levels。我这里不贴，请看那边的说明。
回答by biphobe
Defining resolutions doesn't solve the problem (even in v2.1) - I didn't find any pernament fix for this, so I made my own zoombar in JS - that's what I would recommend to anyone who encounters issues with zoombar using custom tiles.
定义分辨率并不能解决问题（即使在 v2.1 中） - 我没有找到任何永久修复，所以我在 JS 中制作了我自己的缩放栏 - 这就是我向任何遇到使用自定义缩放栏问题的人推荐的瓷砖。
