Class: DataTypeConverter

OpenSeadragon.DataTypeConverter

Methods

new DataTypeConverter()

Class that orchestrates automated data types conversion. Do not instantiate this class, use OpenSeadragon.converter - a global instance, instead. Types are defined to closely describe the data type, e.g. "url" is insufficient, because url can point to many different data types. Another bad example is 'canvas' as canvas can have different underlying rendering implementations and thus differ in behavior. The following data types supported by OpenSeadragon core are: - "image" - HTMLImageElement, an object - "context2d" - HtmlRenderingContext2D, a 2D canvas context - "rasterBlob" - Blob, a binary file-like object carrying image data - "imageBitmap" - an ImageBitmap object The system uses these to deliver desired data from TileSource (which implements fetching logics) through plugins to the renderer with preserving data type compatibility. Typical example is: TiledImage downloads and creates Image object with type 'image'. It submits to the system object of data type 'image'. The system runs this object through possible plugins integrated into the invalidation routine (by default none), and finishes by conversion for the WebGL renderer, which would most likely be "image" object, because the conversion in this case is not even necessary, as the drawer publishes the image type as one of its supported ones. If some plugin required context2d type, the pipeline would deliver this type and used it also for WebGL, as texture loading function accepts canvas object as well as image.
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Methods

convert(tile, data, from, …to) → {OpenSeadragon.Promise.<?>}

Convert data item x of type 'from' to any of the 'to' types, chosen is the cheapest known conversion. Data is destroyed upon conversion. For different behavior, implement your conversion using the path rules obtained from getConversionPath(). Note: conversion DOES NOT COPY data if [to] contains type 'from' (e.g., the cheapest conversion is no conversion). It automatically calls destructor on immediate types, but NOT on the x and the result. You should call these manually if these should be destroyed.
Parameters:
Name Type Attributes Description
tile OpenSeadragon.Tile
data any data item to convert
from string data item type
to string <repeatable>
 desired type(s)
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Returns:
promise resolution with type 'to', or rejection if conversion failed.
Type
OpenSeadragon.Promise.<?>

copy(tile, data, type) → {OpenSeadragon.Promise.<?>|undefined}

Copy the data item given.
Parameters:
Name Type Description
tile OpenSeadragon.Tile
data any data item to convert
type string data type
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Returns:
promise resolution with data passed from constructor
Type
OpenSeadragon.Promise.<?> | undefined

destroy(type, data) → {OpenSeadragon.Promise.<any>|undefined}

Destroy the data item given.
Parameters:
Name Type Description
type string data type
data any
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Returns:
promise resolution with data passed from constructor, or undefined if not such conversion exists
Type
OpenSeadragon.Promise.<any> | undefined

existsType(type) → {boolean}

Check whether given type is known to the converter
Parameters:
Name Type Description
type string type to test
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Returns:
Type
boolean

getConversionPath(from, to) → {Array.<ConversionStep>|undefined}

Get possible system type conversions and cache result.
Parameters:
Name Type Description
from string data item type
to string | Array.<string> array of accepted types
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Returns:
array of required conversions (returns empty array for from===to), or undefined if the system cannot convert between given types. Each object has 'transform' function that converts between neighbouring types, such that x = arr[i].transform(x) is valid input for converter arr[i+1].transform(), e.g. arr[i+1].transform(arr[i].transform( ... )) is a valid conversion procedure. Note: if a function is returned, it is a callback called once the data is ready.
Type
Array.<ConversionStep> | undefined

getConversionPathFinalType(path) → {undefined|string}

Get the final type of the conversion path.
Parameters:
Name Type Description
path Array.<ConversionStep>
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Returns:
undefined if invalid path
Type
undefined | string

getKnownTypes() → {Array.<string>}

Return a list of known conversion types
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Returns:
Type
Array.<string>

learn(from, to, callback, costPoweropt, costMultiplieropt)

Teach the system to convert data type 'from' -> 'to'
Parameters:
Name Type Attributes Default Description
from string unique ID of the data item 'from'
to string unique ID of the data item 'to'
callback OpenSeadragon.TypeConverter converter that takes two arguments: a tile reference, and a data object of a type 'from'; and converts this data object to type 'to'. It can return also the value wrapped in a Promise (returned in resolve) or it can be async function.
costPower Number <optional>
 0 positive cost class of the conversion, smaller or equal than 7. Should reflect the actual cost of the conversion: - if nothing must be done and only reference is retrieved (or a constant operation done), return 0 (default) - if a linear amount of work is necessary, return 1 ... and so on, basically the number in O() complexity power exponent (for simplification)
costMultiplier Number <optional>
 1 multiplier of the cost class, e.g. O(3n^2) would use costPower=2, costMultiplier=3; can be between 1 and 10^5
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learnDestroy(type, callback)

Teach the system to destroy data type 'type' for example, textures loaded to GPU have to be also manually removed when not needed anymore. Needs to be defined only when the created object has extra deletion process.
Parameters:
Name Type Description
type string
callback OpenSeadragon.TypeDestructor destructor, receives the object created, it is basically a type conversion to 'undefined' - thus the type.
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