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Correctly getting tile data for a location.

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The UTFGrid layer's `getTileInfo` method was not correctly handling dateline wrapping (and was a bit more complicated than it needed to be).  Since it would be useful to all grid layers to be able to retrieve a tile and pixel offset for any map location, this functionality deserves to be on the Grid layer.

The WMTS layer currently exposes a `getTileInfo` method that is used within the layer and by the WMTSGetFeatureInfo control.  This method could be renamed to `getRemoteTileInfo` or something to differentiate it from a method that gets locally cached tile info.  Until that change is made, the method on the Grid layer will be called `getGridData`.
This commit is contained in:
Tim Schaub
2012-03-06 16:06:15 -07:00
parent 0e4953efdd
commit 46054b8543
3 changed files with 61 additions and 71 deletions
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2
examples/utfgrid-geography-class.js
View File

@@ -6,7 +6,7 @@ var osm = new OpenLayers.Layer.XYZ(
"http://otile3.mqcdn.com/tiles/1.0.0/osm/${z}/${x}/${y}.png",
"http://otile4.mqcdn.com/tiles/1.0.0/osm/${z}/${x}/${y}.png"
],
{transitionEffect: "resize"}
{transitionEffect: "resize", wrapDateLine: true}
);
var utfgrid = new OpenLayers.Layer.UTFGrid({

58
lib/OpenLayers/Layer/Grid.js
View File

@@ -416,6 +416,64 @@ OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
}
}
},
/**
* Method: getTileData
* Given a map location, retrieve a tile and the pixel offset within that
* tile corresponding to the location. If there is not an existing
* tile in the grid that covers the given location, null will be
* returned.
*
* Parameters:
* loc - {<OpenLayers.LonLat>} map location
*
* Returns:
* {Object} Object with the following properties: tile ({<OpenLayers.Tile>}),
* i ({Number} x-pixel offset from top left), and j ({Integer} y-pixel
* offset from top left).
*/
getTileData: function(loc) {
var data = null,
x = loc.lon,
y = loc.lat,
numRows = this.grid.length;
if (this.map && numRows) {
var res = this.map.getResolution(),
tileWidth = this.tileSize.w,
tileHeight = this.tileSize.h,
bounds = this.grid[0][0].bounds,
left = bounds.left,
top = bounds.top;
if (x < left) {
// deal with multiple worlds
if (this.map.baseLayer.wrapDateLine) {
var worldWidth = this.map.getMaxExtent().getWidth();
var worldsAway = Math.ceil((left - x) / worldWidth);
x += worldWidth * worldsAway;
}
}
// tile distance to location (fractional number of tiles);
var dtx = (x - left) / (res * tileWidth);
var dty = (top - y) / (res * tileHeight);
// index of tile in grid
var col = Math.floor(dtx);
var row = Math.floor(dty);
if (row < numRows) {
var tile = this.grid[row][col];
if (tile) {
data = {
tile: tile,
// pixel index within tile
i: Math.floor((dtx - col) * tileWidth),
j: Math.floor((dty - row) * tileHeight)
};
}
}
}
return data;
},
/**
* Method: queueTileDraw

72
lib/OpenLayers/Layer/UTFGrid.js
View File

@@ -131,74 +131,6 @@ OpenLayers.Layer.UTFGrid = OpenLayers.Class(OpenLayers.Layer.XYZ, {
return obj;
},
/**
* Method: getTileInfo
* Get tile information for a given location at the current map resolution.
*
* Parameters:
* loc - {<OpenLayers.LonLat} A location in map coordinates.
*
* Returns:
* {Object} An object with the following properties
*
* globalCol: the tile's X
*
* globalRow: the tile's Y
*
* gridCol: the viewport grid X
*
* gridRow: the viewpoirt grid Y
*
* tile: the associated OpenLayers.Tile.UTFGrid object
*
* zoom: the tile zoom level
*
* i: the pixel X position relative to the current tile origin
*
* j: the pixel Y position relative to the current tile origin
*/
getTileInfo: function(loc) {
var res = this.getServerResolution();
// Get the global XY for the tile at this zoomlevel
var fx = (loc.lon - this.tileOrigin.lon) / (res * this.tileSize.w);
var fy = (this.tileOrigin.lat - loc.lat) / (res * this.tileSize.h);
var globalCol = Math.floor(fx);
var globalRow = Math.floor(fy);
// Get the current grid offset
var gridOrigin = this.grid[0][0].bounds;
// Floating point math can cause problems (4.9999 should be 5)
// flooring will cause big problems (4.999 becomes 4)...
// Do round or toFixed later?
var gridColOffset =
(gridOrigin.left - this.tileOrigin.lon) / (res * this.tileSize.w);
var gridRowOffset =
(this.tileOrigin.lat - gridOrigin.top) / (res * this.tileSize.h);
// Calculate the grid XY for the tile
var gridCol = globalCol - Math.round(gridColOffset);
var gridRow = globalRow - Math.round(gridRowOffset);
var resolutions = this.serverResolutions || this.resolutions;
var zoom = this.zoomOffset == 0 ?
OpenLayers.Util.indexOf(resolutions, res) :
this.getServerZoom() + this.zoomOffset;
var tile = this.grid[gridRow][gridCol];
return {
globalCol: globalCol,
globalRow: globalRow,
gridCol: gridCol,
gridRow: gridRow,
tile: tile,
zoom: zoom,
i: Math.floor((fx - globalCol) * this.tileSize.w),
j: Math.floor((fy - globalRow) * this.tileSize.h)
};
},
/**
* APIProperty: getFeatureInfo
* Get details about a feature associated with a map location. The object
@@ -215,7 +147,7 @@ OpenLayers.Layer.UTFGrid = OpenLayers.Class(OpenLayers.Layer.XYZ, {
*/
getFeatureInfo: function(location) {
var info = null;
var tileInfo = this.getTileInfo(location);
var tileInfo = this.getTileData(location);
if (tileInfo.tile) {
info = tileInfo.tile.getFeatureInfo(tileInfo.i, tileInfo.j);
}
@@ -235,7 +167,7 @@ OpenLayers.Layer.UTFGrid = OpenLayers.Class(OpenLayers.Layer.XYZ, {
*/
getFeatureId: function(location) {
var id = null;
var info = this.getTileInfo(location);
var info = this.getTileData(location);
if (info.tile) {
id = info.tile.getFeatureId(info.i, info.j);
}