网络地图服务（WMS）

网络地图服务（WMS）利用具有地理空间位置信息的数据制作地图。其中将地图定义为地理数据可视的表现。能够根据用户的请求返回相应的地图（包括PNG，GIF，JPEG等栅格形式或者是SVG和WEB CGM等矢量形式）。WMS支持网络协议HTTP，所支持的操作是由URL定义的。

先来分析一波服务链接：
一般情况给我们的是这样的：http://... .../geoserver/xf/wms?service=WMS&version=1.1.0&request=GetMap&layers=zgwz_lzyz_f08&styles=&bbox=-1844.9489742784644,0.0,35699.99999999942,34437.74999999997&width=768&height=704&srs=EPSG:3857&format=application/openlayers

参数：

service=WMS
version=1.1.0 ： 版本（1.1...和1.3...在计算上有区别）
request=GetMap
layers=zgwz_lzyz_f08 ：图层数组（这个参数如果错误则不显示）
styles=
bbox=-1844.9489742784644,0.0,35699.99999999942,34437.74999999997 : 盒子（显示区域）一般是需要计算
width=768
height=704
srs=EPSG:3857 ：坐标类型：3857同900913为伪墨卡托投影，也被称为球体墨卡托坐标；4326为WGS84经纬度坐标
format=application/openlayers ：格式，iOS用这个format=image/png
TRANSPARENT=TRUE ：透明 true：可以看到高德底图，false看不到高德底图
==>http://... .../geoserver/xf/wms?SERVICE=WMS&VERSION=1.1.0&REQUEST=GetMap&LAYERS=zgwz_lzyz_f08_gd&TRANSPARENT=TRUE&STYLES=&WIDTH=762&HEIGHT=768&srs=EPSG:3857&FORMAT=image/png&BBOX=

一、高德地图:

通过高德地图 MATileOverlay 接口，添加 WMS 服务到地图上

高德

1.自定义类WMSTileOverlay继承自MATileOverlay

import UIKit

class WMSTileOverlay: MATileOverlay {
    var rootURL = ""
    var titleSize = 0
    var initialResolution = 0.0
    var originShift = 0.0
    var HALF_PI = 0.0
    var RAD_PER_DEGREE = 0.0
    var HALF_RAD_PER_DEGREE = 0.0
    var METER_PER_DEGREE = 0.0
    var DEGREE_PER_METER = 0.0
    
    /// 初始化
    /// - Parameter initRootURL: 在线地图路径&TRANSPARENT=TRUE&FORMAT=image/png&BBOX= 
    init?(rootURL initRootURL: String?) {
        super.init()
        rootURL = initRootURL ?? ""
        titleSize = 256
        initialResolution = 156543.03392804062////2*Math.PI*6378137/titleSize
        originShift = 20037508.342789244//周长的一半 2*Math.PI*6378137/2.0
        HALF_PI = .pi / 2.0
        RAD_PER_DEGREE = .pi/180.0
        HALF_RAD_PER_DEGREE = .pi/360.0
        METER_PER_DEGREE = originShift/180.0//一度多少米
        DEGREE_PER_METER = 180.0/originShift//一米多少度
    }

    /**
    * @brief 以tile path生成URL。用于加载tile,此方法默认填充URLTemplate
    * @param path tile path
    * @return 以tile path生成tileOverlay
    */
    override func url(forTilePath path: MATileOverlayPath) -> URL {

        let strURL = "\(rootURL)\(titleBoundsBy(x: path.x, y: path.y, zoom: path.z) ?? "")"
        let url = URL(string: strURL)
        return url!
    }

    /**
    * @brief 加载被请求的tile,并以tile数据或加载tile失败error访问回调block;默认实现为首先用URLForTilePath去获取URL,然后用异步NSURLConnection加载tile
    * @param path   tile path
    * @param result 用来传入tile数据或加载tile失败的error访问的回调block
    */
    override func loadTile(at path: MATileOverlayPath, result: @escaping(Data?, Error?) -> Void) {
        let url = self.url(forTilePath: path)
        let request = NSMutableURLRequest(url: url)
        request.httpMethod = "GET"
        let session = URLSession.shared
        session.dataTask(with: request as URLRequest, completionHandler: {(data, response, error) in
            if error != nil {
                #if DEBUG
                print("Error downloading tile")
                #endif
                result(nil, error)
            }
            else {
                result(data, nil)
            }
        }).resume()
    }
    
    /// 取消请求瓦片，当地图显示区域发生变化时，会取消显示区域外的瓦片的下载, 当disableOffScreenTileLoading=YES时会被调用。since 5.3.0
    /// - Parameter path: path
    override func cancelLoadOfTile(at path: MATileOverlayPath) {
        super.cancelLoadOfTile(at: path)
    }

    /**
    * 根据瓦片的x/y等级返回瓦片范围
    *
    * @param tx
    * @param ty
    * @param zoom
    * @return url
    */
    func titleBoundsBy(x: Int, y: Int, zoom: Int) -> String? {
        let minX = pixels2Meters(x * titleSize, zoom: zoom)
        let maxY = -pixels2Meters(y * titleSize, zoom: zoom)
        let maxX = pixels2Meters(((x + 1) * titleSize), zoom: zoom)
        let minY = -pixels2Meters(((y + 1) * titleSize), zoom: zoom)
        
        return "\(minX),\(minY),\(maxX),\(maxY)"
    }

    /**
    * 根据像素、等级算出坐标
    *
    * @param p p
    * @param zoom z
    * @return double
    */
    func pixels2Meters(_ p: Int, zoom: Int) -> Double {
        return Double(p) * resolution(zoom) - originShift
    }

    /**
    * 计算分辨率
    *
    * @param zoom z
    * @return double
    */
    func resolution(_ zoom: Int) -> Double {
        return initialResolution / (pow(2.0, Double(zoom)))
    }
}

2.在地图控制器MapController调用

import UIKit

class MapController: UIViewController {
    let tileOverlay = WMSTileOverlay.init(rootURL: "http://... .../geoserver/haitu/wms?SERVICE=WMS&VERSION=1.1.0&REQUEST=GetMap&LAYERS=haitu:gis_t_landuse_a&TRANSPARENT=TRUE&STYLES=&srs=EPSG:3857&FORMAT=image/png&BBOX=")
    
    override func viewDidLoad() {
        super.viewDidLoad()
        let map = MAMapView(frame: frame: view.bounds)
        mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        mapView.setCenter(CLLocationCoordinate2D(latitude: 39.97000000, longitude: 116.3300000), zoomLevel: 20, animated: false)
        tileOverlay?.disableOffScreenTileLoading = true//停止不在显示区域的瓦片下载
        mapView.add(tileOverlay)
        view.addSubview(mapView)
    }
}

3.异常处理

（1）WMS服务地图没有坐标：会导致图层不能显示在正确的位置，这时候图层会显示在地图的（0，0）坐标位置（非洲），排查的方法就是将地图中心设置在（0，0）坐标，然后放大。解决办法就是制图工程师给你个带坐标的图。

（2）图层叠加了很多次：第一出现这种情况有可能是我们自己对图层做的缓存引起的。可以删除缓存试试。

（3）出现栅格：这种情况有可能发布的图有问题，或者bbox参数计算出现了问题。出现这种情况的原因很多，欢迎补充。

（4）坐标系不同、WMS版本1.1和1.3：如果WMS服务给的是84坐标系，叠加到高德上会出现偏移，可以让制图工程师出一个高德坐标系的图，也可以我们自己在代码里做，会有一点计算量，代码如下：

在第1步自定义类WMSTileOverlay中的方法func titleBoundsBy(x: Int, y: Int, zoom: Int) -> String?更改

    /**
    * 根据瓦片的x/y等级返回瓦片范围
    *
    * @param tx
    * @param ty
    * @param zoom
    * @return url
    */
    func titleBoundsBy(x: Int, y: Int, zoom: Int) -> String? {
        let minX = pixels2Meters(x * titleSize, zoom: zoom)
        let maxY = -pixels2Meters(y * titleSize, zoom: zoom)
        let maxX = pixels2Meters(((x + 1) * titleSize), zoom: zoom)
        let minY = -pixels2Meters(((y + 1) * titleSize), zoom: zoom)
        
        return "\(minX),\(minY),\(maxX),\(maxY)"
    }

改为

    /**
    * 根据瓦片的x/y等级返回瓦片范围
    *
    * @param tx
    * @param ty
    * @param zoom
    * @return url
    */
    func titleBoundsBy(x: Int, y: Int, zoom: Int) -> String? {
        var minX = pixels2Meters(x * titleSize, zoom: zoom)
        var maxY = -pixels2Meters(y * titleSize, zoom: zoom)
        var maxX = pixels2Meters(((x + 1) * titleSize), zoom: zoom)
        var minY = -pixels2Meters(((y + 1) * titleSize), zoom: zoom)
        
        //转换成经纬度
        minX = meters2Lon(minX)
        minY = meters2Lat(minY)
        maxX = meters2Lon(maxX)
        maxY = meters2Lat(maxY)
        
        //转换目标经纬度为高德坐标系。
        let amapcoord = AMapCoordinateConvert(CLLocationCoordinate2DMake(CLLocationDegrees(minY), CLLocationDegrees(minX)), type)
        minY = amapcoord.latitude
        minX = amapcoord.longitude
        let maxAmapcoord = AMapCoordinateConvert(CLLocationCoordinate2DMake(CLLocationDegrees(maxY), CLLocationDegrees(maxX)), type)
        maxY = maxAmapcoord.latitude
        maxX = maxAmapcoord.longitude
        
        //转换成墨卡托
        minX = lon2Meters(minX)
        minY = lat2Meters(minY)
        maxX = lon2Meters(maxX)
        maxY = lat2Meters(maxY)
        
        //有博客提到1.1版本和1.3版本有区别，没有尝试过，如果你遇到了欢迎补充
        result = "\(minX),\(minY),\(maxX),\(maxY)" //1.1
        //result = "\(minX),\(minY),\(maxX),\(maxY)"//1.3
        
        return result
    }
    
    //////添加坐标转换相应的方法
    /**
    * X米转经纬度
    */
    func meters2Lon(_ mx: Double) -> Double {
        let lon = mx * DEGREE_PER_METER
        return lon
    }

    /**
    * Y米转经纬度
    */
    func meters2Lat(_ my: Double) -> Double {
        var lat = my * DEGREE_PER_METER
        lat = 180.0 / .pi * (2 * atan(exp(lat * RAD_PER_DEGREE)) - HALF_PI)
        return lat
    }
    
    /**
    * X经纬度转米
    */
    func lon2Meters(_ lon: Double) -> Double {
        let mx = lon * METER_PER_DEGREE
        return mx
    }
    
    /**
    * Y经纬度转米
    */
    func lat2Meters(_ lat: Double) -> Double {
        var my = log(tan((90 + lat) * HALF_RAD_PER_DEGREE))/(RAD_PER_DEGREE)
        my = my * METER_PER_DEGREE
        return my
    }

二、Mapbox地图:

建议：做室内地图的用Mapbox，因为Mapbox缩放级别可以达到1米的效果。

image

1.Mapbox的WMS服务和添加栅格图像是一样的，甚至不需要我们做修改,唯一需要注意的是参数：bbox={bbox-epsg-3857}

import UIKit
import Mapbox

class ViewController: UIViewController, MGLMapViewDelegate {
    var mapView: MGLMapView!
    var rasterLayer: MGLRasterStyleLayer?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        mapView = MGLMapView(frame: view.bounds)
        mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        
        mapView.setCenter(CLLocationCoordinate2D(latitude: 39.97000000, longitude: 116.3300000), zoomLevel: 20, animated: false)
        
        mapView.delegate = self
        
        view.addSubview(mapView)
        
        // Add a UISlider that will control the raster layer’s opacity.
        addSlider()
    }
    
    func mapView(_ mapView: MGLMapView, didFinishLoading style: MGLStyle) {
        // Add a new raster source and layer.
        let source = MGLRasterTileSource(identifier: "stamen-watercolor", tileURLTemplates: ["http://.../geoserver/xf/wms?service=WMS&version=1.1.0&request=GetMap&layers=zgwz_lzyz_f08_3857&styles=&bbox={bbox-epsg-3857}&width=768&height=704&srs=EPSG:3857&format=image/png"], options: [ .tileSize: 256 ])
        let rasterLayer = MGLRasterStyleLayer(identifier: "stamen-watercolor", source: source)
        
        style.addSource(source)
        style.addLayer(rasterLayer)
        
        self.rasterLayer = rasterLayer
    }
    
    @objc func updateLayerOpacity(_ sender: UISlider) {
        rasterLayer?.rasterOpacity = NSExpression(forConstantValue: sender.value as NSNumber)
    }
    
    func addSlider() {
        let padding: CGFloat = 10
        let slider = UISlider(frame: CGRect(x: padding, y: self.view.frame.size.height - 44 - 30, width: self.view.frame.size.width - padding *  2, height: 44))
        slider.minimumValue = 0
        slider.maximumValue = 1
        slider.value = 1
        slider.isContinuous = false
        slider.addTarget(self, action: #selector(updateLayerOpacity), for: .valueChanged)
        view.insertSubview(slider, aboveSubview: mapView)
        if #available(iOS 11.0, *) {
            let safeArea = view.safeAreaLayoutGuide
            slider.translatesAutoresizingMaskIntoConstraints = false
            let constraints = [
                slider.bottomAnchor.constraint(equalTo: safeArea.bottomAnchor, constant: -mapView.logoView.bounds.height - 10),
                slider.widthAnchor.constraint(equalToConstant: self.view.frame.size.width - padding *  2),
                slider.centerXAnchor.constraint(equalTo: safeArea.centerXAnchor)
            ]
            
            NSLayoutConstraint.activate(constraints)
        } else {
            slider.autoresizingMask = [.flexibleTopMargin, .flexibleLeftMargin, .flexibleRightMargin]
        }
    }
}

iOS高德地图WMS服务&&mapbox地图WMS服务