Interface IRasterTileLayer

The layer's images have an alpha channel. Default is false.

If a layer's display should not be scale-based, this should be set to true. This will cause the layer, as an overlay, to always be 'active', by always returning true from the calculateInRange() function.

If not explicitly specified for a layer, its value will be determined on startup in initResolutions() based on whether or not any scale-specific properties have been set as options on the layer. If no scale-specific options have been set on the layer, we assume that it should always be in range.

Attribution string, displayed when an <OpenLayers.Control.Attribution> has been added to the map.

Property: backBuffer {DOMElement} The back buffer.

Property: backBufferLonLat {Object} The top-left corner of the current back buffer. Includes lon and lat properties. This object is updated each time a back buffer is created.

Property: backBufferResolution {Number} The resolution of the current back buffer. This property is updated each time a back buffer is created.

Property: backBufferTimerId {Number} The id of the back buffer timer. This timer is used to delay the removal of the back buffer, thereby preventing flash effects caused by tile animation.

APIProperty: buffer {Integer} Used only when in gridded mode, this specifies the number of extra rows and columns of tiles on each side which will surround the minimum grid tiles to cover the map. For very slow loading layers, a larger value may increase performance somewhat when dragging, but will increase bandwidth use significantly.

APIProperty: className {String} Name of the class added to the layer div. If not set in the options passed to the constructor then className defaults to "olLayerGridSingleTile" for single tile layers (see ), and "olLayerGrid" for non single tile layers.

Note:

The displaying of tiles is not animated by default for single tile layers - OpenLayers' default theme (style.css) includes this: (code) .olLayerGrid .olTileImage { -webkit-transition: opacity 0.2s linear; -moz-transition: opacity 0.2s linear; -o-transition: opacity 0.2s linear; transition: opacity 0.2s linear; } (end) To animate tile displaying for any grid layer the following CSS rule can be used: (code) .olTileImage { -webkit-transition: opacity 0.2s linear; -moz-transition: opacity 0.2s linear; -o-transition: opacity 0.2s linear; transition: opacity 0.2s linear; } (end) In that case, to avoid flash effects, should not be zero.

Display the layer's name in the layer switcher. Default is true

Request map tiles that are completely outside of the max extent for this layer. Defaults to false.

An optional object whose properties will be set on the layer. Any of the layer properties can be set as a property of the options object and sent to the constructor when the layer is created.

APIProperty: events {<OpenLayers.Events>}

Register a listener for a particular event with the following syntax: (code) layer.events.register(type, obj, listener); (end)

Listeners will be called with a reference to an event object. The properties of this event depends on exactly what happened.

All event objects have at least the following properties: object - {Object} A reference to layer.events.object. element - {DOMElement} A reference to layer.events.element.

Supported map event types: loadstart - Triggered when layer loading starts. When using a Vector layer with a Fixed or BBOX strategy, the event object includes a filter property holding the OpenLayers.Filter used when calling read on the protocol. loadend - Triggered when layer loading ends. When using a Vector layer with a Fixed or BBOX strategy, the event object includes a response property holding an OpenLayers.Protocol.Response object. visibilitychanged - Triggered when the layer's visibility property is changed, e.g. by turning the layer on or off in the layer switcher. Note that the actual visibility of the layer can also change if it gets out of range (see ). If you also want to catch these cases, register for the map's 'changelayer' event instead. move - Triggered when layer moves (triggered with every mousemove during a drag). moveend - Triggered when layer is done moving, object passed as argument has a zoomChanged boolean property which tells that the zoom has changed. added - Triggered after the layer is added to a map. Listeners will receive an object with a map property referencing the map and a layer property referencing the layer. removed - Triggered after the layer is removed from the map. Listeners will receive an object with a map property referencing the map and a layer property referencing the layer.

Property: grid {Array(Array(<OpenLayers.Tile>))} This is an array of rows, each row is an array of tiles.

Property: gridLayout {Object} Object containing properties tilelon, tilelat, startcol, startrow

Property: gridResolution {Number} The resolution of the current grid. Used for backbuffer and client zoom. This property is updated every time the grid is initialized.

Determines the width (in pixels) of the gutter around image tiles to ignore. By setting this property to a non-zero value, images will be requested that are wider and taller than the tile size by a value of 2 x gutter. This allows artifacts of rendering at tile edges to be ignored. Set a gutter value that is equal to half the size of the widest symbol that needs to be displayed. Defaults to zero. Non-tiled layers always have zero gutter.

For layers with a gutter, the image is larger than the tile by twice the gutter in each dimension.

The current map resolution is within the layer's min/max range. This is set in <OpenLayers.Map.setCenter> whenever the zoom changes.

APIProperty: isBaseLayer Default is true, as this is designed to be a base tile source.

Property: loading {Boolean} Indicates if tiles are being loaded.

This variable is set when the layer is added to the map, via the accessor function setMap()

The maximum extent for the layer. Defaults to null.

Default max is 360 deg / 256 px, which corresponds to zoom level 0 on gmaps. Specify a different value in the layer options if you are not using the default <OpenLayers.Map.tileSize> and displaying the whole world.

This object can be used to store additional information on a layer object.

The minimum extent for the layer. Defaults to null.

APIProperty: numLoadingTiles {Integer} How many tiles are still loading?

The layer's opacity. Float number between 0.0 and 1.0.

An optional object whose properties will be set on the layer. Any of the layer properties can be set as a property of the options object and sent to the constructor when the layer is created.

Property: params {Object} Hashtable of key/value parameters

Specifies the projection of the layer. Can be set in the layer options. If not specified in the layer options, it is set to the default projection specified in the map, when the layer is added to the map. Projection along with default maxExtent and resolutions are set automatically with commercial baselayers in EPSG:3857, such as Google, Bing and OpenStreetMap, and do not need to be specified. Otherwise, if specifying projection, also set maxExtent, maxResolution or resolutions as appropriate. When using vector layers with strategies, layer projection should be set to the projection of the source data if that is different from the map default.

APIProperty: ratio {Float} Used only when in single-tile mode, this specifies the ratio of the size of the single tile to the size of the map. Default value is 1.5.

APIProperty: removeBackBufferDelay {Number} Delay for removing the backbuffer when all tiles have finished loading. Can be set to 0 when no css opacity transitions for the olTileImage class are used. Default is 0 for layers, 2500 for tiled layers. See for more information on tile animation.

APIProperty: reproject Deprecated. See http://docs.openlayers.org/library/spherical_mercator.html for information on the replacement for this functionality. {Boolean} Whether layer should reproject itself based on base layer locations. This allows reprojection onto commercial layers. Default is false: Most layers can't reproject, but layers which can create non-square geographic pixels can, like WMS.

The properties that are used for calculating resolutions information.

A list of map resolutions (map units per pixel) in descending order. If this is not set in the layer constructor, it will be set based on other resolution related properties (maxExtent, maxResolution, maxScale, etc.).

Property: rowSign {Number} 1 for grids starting at the top, -1 for grids starting at the bottom. This is used for several grid index and offset calculations.

An array of map scales in descending order. The values in the array correspond to the map scale denominator. Note that these values only make sense if the display (monitor) resolution of the client is correctly guessed by whomever is configuring the application. In addition, the units property must also be set. Use instead wherever possible.

APIProperty: serverResolutions {Array} A list of all resolutions available on the server. Only set this property if the map resolutions differ from the server. This property serves two purposes. (a) can include resolutions that the server supports and that you don't want to provide with this layer; you can also look at , which is an alternative to for that specific purpose. (b) The map can work with resolutions that aren't supported by the server, i.e. that aren't in . When the map is displayed in such a resolution data for the closest server-supported resolution is loaded and the layer div is stretched as necessary.

APIProperty: singleTile {Boolean} Moves the layer into single-tile mode, meaning that one tile will be loaded. The tile's size will be determined by the 'ratio' property. When the tile is dragged such that it does not cover the entire viewport, it is reloaded.

APIProperty: sphericalMercator Whether the tile extents should be set to the defaults for spherical mercator. Useful for things like OpenStreetMap. Default is false, except for the OSM subclass.

APIProperty: tileClass {<OpenLayers.Tile>} The tile class to use for this layer. Defaults is OpenLayers.Tile.Image.

APIProperty: tileOptions {Object} optional configuration options for <OpenLayers.Tile> instances created by this Layer, if supported by the tile class.

APIProperty: tileOrigin {<OpenLayers.LonLat>} Optional origin for aligning the grid of tiles. If provided, requests for tiles at all resolutions will be aligned with this location (no tiles shall overlap this location). If not provided, the grid of tiles will be aligned with the layer's . Default is null.

Property: tileOriginCorner {String} If the property is not provided, the tile origin will be derived from the layer's . The corner of the used is determined by this property. Acceptable values are "tl" (top left), "tr" (top right), "bl" (bottom left), and "br" (bottom right). Default is "bl".

APIProperty: tileSize {<OpenLayers.Size>}

APIProperty: transitionEffect {String} The transition effect to use when the map is zoomed. Two posible values:

"resize" - Existing tiles are resized on zoom to provide a visual effect of the zoom having taken place immediately. As the new tiles become available, they are drawn on top of the resized tiles (this is the default setting). "map-resize" - Existing tiles are resized on zoom and placed below the base layer. New tiles for the base layer will cover existing tiles. This setting is recommended when having an overlay duplicated during the transition is undesirable (e.g. street labels or big transparent fills). null - No transition effect.

Using "resize" on non-opaque layers can cause undesired visual effects. Set transitionEffect to null in this case.

Property: transitionendEvents {Array} Event names for transitionend

The layer map units. Defaults to null. Possible values are 'degrees' (or 'dd'), 'm', 'ft', 'km', 'mi', 'inches'. Normally taken from the projection. Only required if both map and layers do not define a projection, or if they define a projection which does not define units.

Property: url {Array(String) or String} This is either an array of url strings or a single url string.

The layer should be displayed in the map. Default is true.

Wraps the world at the international dateline, so the map can be panned infinitely in longitudinal direction. Only use this on the base layer, and only if the layer's maxExtent equals the world bounds.

APIProperty: zoomOffset {Number} If your cache has more zoom levels than you want to provide access to with this layer, supply a zoomOffset. This zoom offset is added to the current map zoom level to determine the level for a requested tile. For example, if you supply a zoomOffset of 3, when the map is at the zoom 0, tiles will be requested from level 3 of your cache. Default is 0 (assumes cache level and map zoom are equivalent). Using is an alternative to setting if you only want to expose a subset of the server resolutions.