Refactor ol.source.ImageWMS URL logic

* Always request images of integer WIDTH and HEIGHT
* Match BBOX to requested size
* Handle integer-only DPIs in GeoServer

src/ol/source/imagewmssource.js

@@ -1,43 +1,48 @@
+// FIXME factor out v13 calculation
+
 goog.provide('ol.source.ImageWMS');
 
 goog.require('goog.asserts');
 goog.require('goog.object');
+goog.require('goog.string');
+goog.require('goog.uri.utils');
 goog.require('ol.Image');
-goog.require('ol.ImageUrlFunction');
 goog.require('ol.extent');
 goog.require('ol.source.Image');
-goog.require('ol.source.wms');
+goog.require('ol.source.wms.ServerType');
 
 
 
 /**
  * @constructor
  * @extends {ol.source.Image}
- * @param {olx.source.ImageWMSOptions} options Options.
+ * @param {olx.source.ImageWMSOptions=} opt_options Options.
  * @todo stability experimental
  */
-ol.source.ImageWMS = function(options) {
+ol.source.ImageWMS = function(opt_options) {
 
-  /**
-   * @private
-   * @type {Object}
-   */
-  this.params_ = options.params;
-
-  var imageUrlFunction = goog.isDef(options.url) ?
-      ol.ImageUrlFunction.createFromParamsFunction(
-          options.url, this.params_, ol.source.wms.getUrl) :
-      ol.ImageUrlFunction.nullImageUrlFunction;
+  var options = goog.isDef(opt_options) ? opt_options : {};
 
   goog.base(this, {
     attributions: options.attributions,
     crossOrigin: options.crossOrigin,
     extent: options.extent,
     projection: options.projection,
-    resolutions: options.resolutions,
-    imageUrlFunction: imageUrlFunction
+    resolutions: options.resolutions
   });
 
+  /**
+   * @private
+   * @type {string|undefined}
+   */
+  this.url_ = options.url;
+
+  /**
+   * @private
+   * @type {Object}
+   */
+  this.params_ = options.params;
+
   /**
    * @private
    * @type {ol.source.wms.ServerType|undefined}
@@ -81,8 +86,16 @@ ol.source.ImageWMS.prototype.getParams = function() {
  */
 ol.source.ImageWMS.prototype.getImage =
     function(extent, resolution, pixelRatio, projection) {
+
+  if (!goog.isDef(this.url_)) {
+    return null;
+  }
+
   resolution = this.findNearestResolution(resolution);
-  pixelRatio = this.hidpi_ ? pixelRatio : 1;
+
+  if (pixelRatio != 1 && (!this.hidpi_ || !goog.isDef(this.serverType_))) {
+    pixelRatio = 1;
+  }
 
   var image = this.image_;
   if (!goog.isNull(image) &&
@@ -92,20 +105,83 @@ ol.source.ImageWMS.prototype.getImage =
     return image;
   }
 
-  extent = extent.slice();
-  ol.extent.scaleFromCenter(extent, this.ratio_);
-  var width = (extent[2] - extent[0]) / resolution;
-  var height = (extent[3] - extent[1]) / resolution;
-  var size = [width * pixelRatio, height * pixelRatio];
+  var params = {
+    'SERVICE': 'WMS',
+    'VERSION': '1.3.0',
+    'REQUEST': 'GetMap',
+    'FORMAT': 'image/png',
+    'TRANSPARENT': true
+  };
+  goog.object.extend(params, this.params_);
 
-  if (goog.isDef(this.serverType_) && pixelRatio > 1) {
-    var param = ol.source.wms.getDpiParam(this.serverType_, pixelRatio);
-    goog.object.extend(this.params_, param);
+  var v13 = goog.string.compareVersions(
+      goog.object.get(params, 'VERSION'), '1.3') >= 0;
+
+  params[v13 ? 'CRS' : 'SRS'] = projection.getCode();
+
+  if (!('STYLES' in this.params_)) {
+    goog.object.set(params, 'STYLES', new String(''));
   }
 
-  this.image_ = this.createImage(
-      extent, resolution, pixelRatio, size, projection);
+  if (pixelRatio != 1) {
+    switch (this.serverType_) {
+      case ol.source.wms.ServerType.GEOSERVER:
+        var dpi = (90 * pixelRatio + 0.5) | 0;
+        goog.object.set(params, 'FORMAT_OPTIONS', 'dpi:' + dpi);
+        break;
+      case ol.source.wms.ServerType.MAPSERVER:
+        goog.object.set(params, 'MAP_RESOLUTION', 90 * pixelRatio);
+        break;
+      case ol.source.wms.ServerType.QGIS:
+        goog.object.set(params, 'DPI', 90 * pixelRatio);
+        break;
+      default:
+        goog.asserts.fail();
+        break;
+    }
+  }
+
+  extent = extent.slice();
+  var centerX = (extent[0] + extent[2]) / 2;
+  var centerY = (extent[1] + extent[3]) / 2;
+  if (this.ratio_ != 1) {
+    var halfWidth = this.ratio_ * (extent[2] - extent[0]) / 2;
+    var halfHeight = this.ratio_ * (extent[3] - extent[1]) / 2;
+    extent[0] = centerX - halfWidth;
+    extent[1] = centerY - halfHeight;
+    extent[2] = centerX + halfWidth;
+    extent[3] = centerY + halfHeight;
+  }
+
+  var imageResolution = resolution / pixelRatio;
+
+  // Compute an integer width and height.
+  var width = Math.ceil((extent[2] - extent[0]) / imageResolution);
+  goog.object.set(params, 'WIDTH', width);
+  var height = Math.ceil((extent[3] - extent[1]) / imageResolution);
+  goog.object.set(params, 'HEIGHT', height);
+
+  // Modify the extent to match the integer width and height.
+  extent[0] = centerX - imageResolution * width / 2;
+  extent[2] = centerX + imageResolution * width / 2;
+  extent[1] = centerY - imageResolution * height / 2;
+  extent[3] = centerY + imageResolution * height / 2;
+
+  var axisOrientation = projection.getAxisOrientation();
+  var bbox;
+  if (v13 && axisOrientation.substr(0, 2) == 'ne') {
+    bbox = [extent[1], extent[0], extent[3], extent[2]];
+  } else {
+    bbox = extent;
+  }
+  goog.object.set(params, 'BBOX', bbox.join(','));
+
+  var url = goog.uri.utils.appendParamsFromMap(this.url_, params);
+
+  this.image_ = new ol.Image(extent, resolution, pixelRatio, url,
+      this.crossOrigin, this.getAttributions());
   return this.image_;
+
 };