本文介绍了OpenLayers 3中是否有一个"getZoomForResolution"?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
OpenLayers 2曾经有一种getZoomForResolution
方法,可以为您提供给定分辨率的缩放级别(或最接近的缩放级别).
OpenLayers 2 used to have a getZoomForResolution
method that would give you the zoom level (or closest zoom level) of a given resolution.
对于ol.View
对象,我在ol3中没有看到任何这样的方法.有没有一种方法可以利用ol.view
当前拥有的东西来实现?
I don't see any such method in ol3, for the ol.View
object that is. Is there a way to achieve this with what ol.view
currently have ?
推荐答案
这将为给定分辨率提供下一个最接近的整数缩放:
This will give the next closest integer zoom for a give resolution:
function zoomForResolution(resolution) {
var zoom = 0;
var r = 156543.03390625; // resolution for zoom 0
while (resolution < r) {
r /= 2;
zoom++;
if (resolution > r) {
return zoom;
}
}
return zoom; // resolution was greater than 156543.03390625 so return 0
}
zoomForResolution(40); // 12
我的兄弟建议:
var zoom = Math.ceil( (Math.log(resolution) - Math.log(156543.03390625) ) / Math.log(0.5))
使用Math.log2()为浏览器完善对数解决方案
refining the logarithmic solution for browsers with Math.log2()
var zoom = Math.log2(156543.03390625) - Math.log2(resolution);
,对于没有log2()的IE
and for IE which does not have log2()
var zoom = Math.log(156543.03390625) * Math.LOG2E - Math.log(resolution) * Math.LOG2E;
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