[76] | 1 | /* Copyright (c) 2006-2010 by OpenLayers Contributors (see authors.txt for |
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| 2 | * full list of contributors). Published under the Clear BSD license. |
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| 3 | * See http://svn.openlayers.org/trunk/openlayers/license.txt for the |
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| 4 | * full text of the license. */ |
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| 5 | |
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| 6 | /** |
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| 7 | * @requires OpenLayers/Layer.js |
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| 8 | */ |
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| 9 | |
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| 10 | /** |
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| 11 | * Class: OpenLayers.Layer.FixedZoomLevels |
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| 12 | * Some Layers will already have established zoom levels (like google |
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| 13 | * or ve). Instead of trying to determine them and populate a resolutions[] |
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| 14 | * Array with those values, we will hijack the resolution functionality |
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| 15 | * here. |
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| 16 | * |
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| 17 | * When you subclass FixedZoomLevels: |
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| 18 | * |
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| 19 | * The initResolutions() call gets nullified, meaning no resolutions[] array |
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| 20 | * is set up. Which would be a big problem getResolution() in Layer, since |
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| 21 | * it merely takes map.zoom and indexes into resolutions[]... but.... |
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| 22 | * |
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| 23 | * The getResolution() call is also overridden. Instead of using the |
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| 24 | * resolutions[] array, we simply calculate the current resolution based |
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| 25 | * on the current extent and the current map size. But how will we be able |
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| 26 | * to calculate the current extent without knowing the resolution...? |
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| 27 | * |
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| 28 | * The getExtent() function is also overridden. Instead of calculating extent |
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| 29 | * based on the center point and the current resolution, we instead |
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| 30 | * calculate the extent by getting the lonlats at the top-left and |
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| 31 | * bottom-right by using the getLonLatFromViewPortPx() translation function, |
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| 32 | * taken from the pixel locations (0,0) and the size of the map. But how |
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| 33 | * will we be able to do lonlat-px translation without resolution....? |
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| 34 | * |
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| 35 | * The getZoomForResolution() method is overridden. Instead of indexing into |
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| 36 | * the resolutions[] array, we call OpenLayers.Layer.getExent(), passing in |
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| 37 | * the desired resolution. With this extent, we then call getZoomForExtent() |
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| 38 | * |
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| 39 | * |
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| 40 | * Whenever you implement a layer using OpenLayers.Layer.FixedZoomLevels, |
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| 41 | * it is your responsibility to provide the following three functions: |
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| 42 | * |
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| 43 | * - getLonLatFromViewPortPx |
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| 44 | * - getViewPortPxFromLonLat |
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| 45 | * - getZoomForExtent |
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| 46 | * |
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| 47 | * ...those three functions should generally be provided by any reasonable |
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| 48 | * API that you might be working from. |
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| 49 | * |
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| 50 | */ |
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| 51 | OpenLayers.Layer.FixedZoomLevels = OpenLayers.Class({ |
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| 52 | |
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| 53 | /********************************************************/ |
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| 54 | /* */ |
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| 55 | /* Baselayer Functions */ |
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| 56 | /* */ |
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| 57 | /* The following functions must all be implemented */ |
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| 58 | /* by all base layers */ |
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| 59 | /* */ |
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| 60 | /********************************************************/ |
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| 61 | |
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| 62 | /** |
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| 63 | * Constructor: OpenLayers.Layer.FixedZoomLevels |
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| 64 | * Create a new fixed zoom levels layer. |
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| 65 | */ |
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| 66 | initialize: function() { |
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| 67 | //this class is only just to add the following functions... |
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| 68 | // nothing to actually do here... but it is probably a good |
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| 69 | // idea to have layers that use these functions call this |
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| 70 | // inititalize() anyways, in case at some point we decide we |
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| 71 | // do want to put some functionality or state in here. |
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| 72 | }, |
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| 73 | |
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| 74 | /** |
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| 75 | * Method: initResolutions |
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| 76 | * Populate the resolutions array |
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| 77 | */ |
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| 78 | initResolutions: function() { |
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| 79 | |
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| 80 | var props = new Array('minZoomLevel', 'maxZoomLevel', 'numZoomLevels'); |
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| 81 | |
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| 82 | for(var i=0, len=props.length; i<len; i++) { |
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| 83 | var property = props[i]; |
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| 84 | this[property] = (this.options[property] != null) |
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| 85 | ? this.options[property] |
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| 86 | : this.map[property]; |
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| 87 | } |
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| 88 | |
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| 89 | if ( (this.minZoomLevel == null) || |
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| 90 | (this.minZoomLevel < this.MIN_ZOOM_LEVEL) ){ |
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| 91 | this.minZoomLevel = this.MIN_ZOOM_LEVEL; |
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| 92 | } |
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| 93 | |
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| 94 | // |
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| 95 | // At this point, we know what the minimum desired zoom level is, and |
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| 96 | // we must calculate the total number of zoom levels. |
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| 97 | // |
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| 98 | // Because we allow for the setting of either the 'numZoomLevels' |
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| 99 | // or the 'maxZoomLevel' properties... on either the layer or the |
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| 100 | // map, we have to define some rules to see which we take into |
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| 101 | // account first in this calculation. |
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| 102 | // |
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| 103 | // The following is the precedence list for these properties: |
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| 104 | // |
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| 105 | // (1) numZoomLevels set on layer |
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| 106 | // (2) maxZoomLevel set on layer |
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| 107 | // (3) numZoomLevels set on map |
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| 108 | // (4) maxZoomLevel set on map* |
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| 109 | // (5) none of the above* |
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| 110 | // |
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| 111 | // *Note that options (4) and (5) are only possible if the user |
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| 112 | // _explicitly_ sets the 'numZoomLevels' property on the map to |
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| 113 | // null, since it is set by default to 16. |
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| 114 | // |
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| 115 | |
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| 116 | // |
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| 117 | // Note to future: In 3.0, I think we should remove the default |
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| 118 | // value of 16 for map.numZoomLevels. Rather, I think that value |
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| 119 | // should be set as a default on the Layer.WMS class. If someone |
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| 120 | // creates a 3rd party layer and does not specify any 'minZoomLevel', |
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| 121 | // 'maxZoomLevel', or 'numZoomLevels', and has not explicitly |
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| 122 | // specified any of those on the map object either.. then I think |
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| 123 | // it is fair to say that s/he wants all the zoom levels available. |
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| 124 | // |
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| 125 | // By making map.numZoomLevels *null* by default, that will be the |
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| 126 | // case. As it is, I don't feel comfortable changing that right now |
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| 127 | // as it would be a glaring API change and actually would probably |
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| 128 | // break many peoples' codes. |
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| 129 | // |
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| 130 | |
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| 131 | //the number of zoom levels we'd like to have. |
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| 132 | var desiredZoomLevels; |
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| 133 | |
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| 134 | //this is the maximum number of zoom levels the layer will allow, |
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| 135 | // given the specified starting minimum zoom level. |
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| 136 | var limitZoomLevels = this.MAX_ZOOM_LEVEL - this.minZoomLevel + 1; |
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| 137 | |
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| 138 | if ( ((this.options.numZoomLevels == null) && |
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| 139 | (this.options.maxZoomLevel != null)) // (2) |
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| 140 | || |
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| 141 | ((this.numZoomLevels == null) && |
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| 142 | (this.maxZoomLevel != null)) // (4) |
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| 143 | ) { |
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| 144 | //calculate based on specified maxZoomLevel (on layer or map) |
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| 145 | desiredZoomLevels = this.maxZoomLevel - this.minZoomLevel + 1; |
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| 146 | } else { |
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| 147 | //calculate based on specified numZoomLevels (on layer or map) |
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| 148 | // this covers cases (1) and (3) |
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| 149 | desiredZoomLevels = this.numZoomLevels; |
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| 150 | } |
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| 151 | |
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| 152 | if (desiredZoomLevels != null) { |
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| 153 | //Now that we know what we would *like* the number of zoom levels |
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| 154 | // to be, based on layer or map options, we have to make sure that |
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| 155 | // it does not conflict with the actual limit, as specified by |
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| 156 | // the constants on the layer itself (and calculated into the |
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| 157 | // 'limitZoomLevels' variable). |
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| 158 | this.numZoomLevels = Math.min(desiredZoomLevels, limitZoomLevels); |
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| 159 | } else { |
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| 160 | // case (5) -- neither 'numZoomLevels' not 'maxZoomLevel' was |
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| 161 | // set on either the layer or the map. So we just use the |
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| 162 | // maximum limit as calculated by the layer's constants. |
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| 163 | this.numZoomLevels = limitZoomLevels; |
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| 164 | } |
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| 165 | |
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| 166 | //now that the 'numZoomLevels' is appropriately, safely set, |
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| 167 | // we go back and re-calculate the 'maxZoomLevel'. |
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| 168 | this.maxZoomLevel = this.minZoomLevel + this.numZoomLevels - 1; |
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| 169 | |
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| 170 | if (this.RESOLUTIONS != null) { |
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| 171 | var resolutionsIndex = 0; |
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| 172 | this.resolutions = []; |
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| 173 | for(var i= this.minZoomLevel; i <= this.maxZoomLevel; i++) { |
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| 174 | this.resolutions[resolutionsIndex++] = this.RESOLUTIONS[i]; |
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| 175 | } |
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| 176 | this.maxResolution = this.resolutions[0]; |
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| 177 | this.minResolution = this.resolutions[this.resolutions.length - 1]; |
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| 178 | } |
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| 179 | }, |
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| 180 | |
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| 181 | /** |
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| 182 | * APIMethod: getResolution |
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| 183 | * Get the current map resolution |
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| 184 | * |
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| 185 | * Returns: |
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| 186 | * {Float} Map units per Pixel |
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| 187 | */ |
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| 188 | getResolution: function() { |
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| 189 | |
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| 190 | if (this.resolutions != null) { |
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| 191 | return OpenLayers.Layer.prototype.getResolution.apply(this, arguments); |
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| 192 | } else { |
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| 193 | var resolution = null; |
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| 194 | |
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| 195 | var viewSize = this.map.getSize(); |
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| 196 | var extent = this.getExtent(); |
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| 197 | |
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| 198 | if ((viewSize != null) && (extent != null)) { |
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| 199 | resolution = Math.max( extent.getWidth() / viewSize.w, |
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| 200 | extent.getHeight() / viewSize.h ); |
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| 201 | } |
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| 202 | return resolution; |
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| 203 | } |
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| 204 | }, |
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| 205 | |
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| 206 | /** |
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| 207 | * APIMethod: getExtent |
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| 208 | * Calculates using px-> lonlat translation functions on tl and br |
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| 209 | * corners of viewport |
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| 210 | * |
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| 211 | * Returns: |
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| 212 | * {<OpenLayers.Bounds>} A Bounds object which represents the lon/lat |
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| 213 | * bounds of the current viewPort. |
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| 214 | */ |
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| 215 | getExtent: function () { |
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| 216 | var extent = null; |
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| 217 | |
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| 218 | |
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| 219 | var size = this.map.getSize(); |
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| 220 | |
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| 221 | var tlPx = new OpenLayers.Pixel(0,0); |
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| 222 | var tlLL = this.getLonLatFromViewPortPx(tlPx); |
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| 223 | |
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| 224 | var brPx = new OpenLayers.Pixel(size.w, size.h); |
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| 225 | var brLL = this.getLonLatFromViewPortPx(brPx); |
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| 226 | |
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| 227 | if ((tlLL != null) && (brLL != null)) { |
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| 228 | extent = new OpenLayers.Bounds(tlLL.lon, |
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| 229 | brLL.lat, |
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| 230 | brLL.lon, |
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| 231 | tlLL.lat); |
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| 232 | } |
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| 233 | |
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| 234 | return extent; |
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| 235 | }, |
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| 236 | |
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| 237 | /** |
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| 238 | * Method: getZoomForResolution |
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| 239 | * Get the zoom level for a given resolution |
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| 240 | * |
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| 241 | * Parameters: |
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| 242 | * resolution - {Float} |
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| 243 | * |
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| 244 | * Returns: |
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| 245 | * {Integer} A suitable zoom level for the specified resolution. |
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| 246 | * If no baselayer is set, returns null. |
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| 247 | */ |
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| 248 | getZoomForResolution: function(resolution) { |
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| 249 | |
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| 250 | if (this.resolutions != null) { |
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| 251 | return OpenLayers.Layer.prototype.getZoomForResolution.apply(this, arguments); |
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| 252 | } else { |
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| 253 | var extent = OpenLayers.Layer.prototype.getExtent.apply(this, []); |
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| 254 | return this.getZoomForExtent(extent); |
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| 255 | } |
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| 256 | }, |
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| 257 | |
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| 258 | |
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| 259 | |
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| 260 | |
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| 261 | /********************************************************/ |
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| 262 | /* */ |
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| 263 | /* Translation Functions */ |
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| 264 | /* */ |
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| 265 | /* The following functions translate GMaps and OL */ |
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| 266 | /* formats for Pixel, LonLat, Bounds, and Zoom */ |
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| 267 | /* */ |
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| 268 | /********************************************************/ |
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| 269 | |
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| 270 | |
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| 271 | // |
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| 272 | // TRANSLATION: MapObject Zoom <-> OpenLayers Zoom |
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| 273 | // |
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| 274 | |
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| 275 | /** |
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| 276 | * Method: getOLZoomFromMapObjectZoom |
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| 277 | * Get the OL zoom index from the map object zoom level |
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| 278 | * |
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| 279 | * Parameters: |
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| 280 | * moZoom - {Integer} |
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| 281 | * |
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| 282 | * Returns: |
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| 283 | * {Integer} An OpenLayers Zoom level, translated from the passed in zoom |
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| 284 | * Returns null if null value is passed in |
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| 285 | */ |
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| 286 | getOLZoomFromMapObjectZoom: function(moZoom) { |
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| 287 | var zoom = null; |
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| 288 | if (moZoom != null) { |
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| 289 | zoom = moZoom - this.minZoomLevel; |
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| 290 | } |
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| 291 | return zoom; |
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| 292 | }, |
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| 293 | |
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| 294 | /** |
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| 295 | * Method: getMapObjectZoomFromOLZoom |
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| 296 | * Get the map object zoom level from the OL zoom level |
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| 297 | * |
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| 298 | * Parameters: |
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| 299 | * olZoom - {Integer} |
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| 300 | * |
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| 301 | * Returns: |
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| 302 | * {Integer} A MapObject level, translated from the passed in olZoom |
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| 303 | * Returns null if null value is passed in |
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| 304 | */ |
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| 305 | getMapObjectZoomFromOLZoom: function(olZoom) { |
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| 306 | var zoom = null; |
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| 307 | if (olZoom != null) { |
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| 308 | zoom = olZoom + this.minZoomLevel; |
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| 309 | } |
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| 310 | return zoom; |
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| 311 | }, |
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| 312 | |
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| 313 | CLASS_NAME: "OpenLayers.Layer.FixedZoomLevels" |
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| 314 | }); |
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| 315 | |
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