Class OffscreenCanvasAdapter

OffscreenCanvas canvas adapter. This can only run inside a web worker.

Hierarchy

OffscreenCanvasAdapter

Implements

CanvasAdapter

Index

Constructors

Methods

create createImage createImageData disposeCanvas disposeImage drawText getImageData initialize isInitialized measureText mergeCanvas scaleImage scaleImageToDimensions toBytes toDataURL writeImageToBytes

Constructors

constructor

new OffscreenCanvasAdapter(): OffscreenCanvasAdapter
Returns OffscreenCanvasAdapter

Methods

create

create(width: number, height: number): OffscreenCanvas
Creates a canvas object
Parameters
- width: number
- height: number
Returns OffscreenCanvas
Implementation of CanvasAdapter.create
- Defined in lib/canvas/offscreenCanvasAdapter.ts:32

createImage

createImage(data: string | Buffer | Uint8Array | Blob, contentType?: string): Promise<GeoPackageImage>
Creates an Image object to be used in the context.drawImage function
Parameters
- data: string | Buffer | Uint8Array | Blob
- contentType: string = 'image/png'
Returns Promise<GeoPackageImage>
Implementation of CanvasAdapter.createImage
- Defined in lib/canvas/offscreenCanvasAdapter.ts:39

createImageData

createImageData(width: any, height: any): ImageData
Creates an ImageData object
Parameters
- width: any
- height: any
Returns ImageData
Implementation of CanvasAdapter.createImageData
- Defined in lib/canvas/offscreenCanvasAdapter.ts:62

disposeCanvas

disposeCanvas(canvas: OffscreenCanvas): void
Performs any cleanup needed for the specified canvas. The canvas should not be used after calling this function.
Parameters
- canvas: OffscreenCanvas
Returns void
Implementation of CanvasAdapter.disposeCanvas
- Defined in lib/canvas/offscreenCanvasAdapter.ts:69

disposeImage

disposeImage(image: GeoPackageImage): void
Performs any cleanup needed for the specified image
Parameters
- image: GeoPackageImage
Returns void
Implementation of CanvasAdapter.disposeImage
- Defined in lib/canvas/offscreenCanvasAdapter.ts:155

drawText

drawText(context: any, text: string, location: number[], fontFace: string, fontSize: number, fontColor: string): void
Draws text centered at the location specified in the canvas rendering context
Parameters
- context: any
- text: string
- location: number[]
- fontFace: string
- fontSize: number
- fontColor: string
Returns void
Implementation of CanvasAdapter.drawText
- Defined in lib/canvas/offscreenCanvasAdapter.ts:90

getImageData

getImageData(image: GeoPackageImage): ImageData
Gets the image data
Parameters
- image: GeoPackageImage
Returns ImageData
Implementation of CanvasAdapter.getImageData
- Defined in lib/canvas/offscreenCanvasAdapter.ts:176

initialize

initialize(): Promise<void>
Initializes the adapter for use.

Returns Promise<void>
Implementation of CanvasAdapter.initialize
- Defined in lib/canvas/offscreenCanvasAdapter.ts:15

isInitialized

isInitialized(): boolean
Returns if the Adapter has been initialized.

Returns boolean
Implementation of CanvasAdapter.isInitialized
- Defined in lib/canvas/offscreenCanvasAdapter.ts:25

measureText

measureText(context: any, fontFace: string, fontSize: number, text: string): number
Returns the width of the text in the given font face and font size
Parameters
- context: any
- fontFace: string
- fontSize: number
- text: string
Returns number
Implementation of CanvasAdapter.measureText
- Defined in lib/canvas/offscreenCanvasAdapter.ts:77

mergeCanvas

mergeCanvas(fromCanvas: any, toContext: any): void
Draw content of fromCanvas into the toContext
Parameters
- fromCanvas: any
- toContext: any
Returns void
Implementation of CanvasAdapter.mergeCanvas
- Defined in lib/canvas/offscreenCanvasAdapter.ts:188

scaleImage

scaleImage(image: GeoPackageImage, scale: number): Promise<GeoPackageImage>
Scales an image created using this adapter.
Parameters
- image: GeoPackageImage
- scale: number
Returns Promise<GeoPackageImage>
Implementation of CanvasAdapter.scaleImage
- Defined in lib/canvas/offscreenCanvasAdapter.ts:110

scaleImageToDimensions

scaleImageToDimensions(image: GeoPackageImage, scaledWidth: number, scaledHeight: number): Promise<GeoPackageImage>
Scales an image created using this adapter.
Parameters
- image: GeoPackageImage
- scaledWidth: number
- scaledHeight: number
Returns Promise<GeoPackageImage>
Implementation of CanvasAdapter.scaleImageToDimensions
- Defined in lib/canvas/offscreenCanvasAdapter.ts:122

toBytes

toBytes(canvas: any, imageFormat: ImageType, compressionQuality?: number): Promise<Uint8Array>
Converts the contents drawn in a canvas to a byte array

Returns
Uint8Array
Parameters
- canvas: any
- imageFormat: ImageType
- Optional compressionQuality: number
Returns Promise<Uint8Array>
Implementation of CanvasAdapter.toBytes
- Defined in lib/canvas/offscreenCanvasAdapter.ts:199

toDataURL

toDataURL(canvas: any, format?: string, compressionQuality?: number): Promise<string>
Converts the canvas to a base64 data url in the format specified
Parameters
- canvas: any
- format: string = 'image/png'
- Optional compressionQuality: number
  
  0 to 1
Returns Promise<string>
Implementation of CanvasAdapter.toDataURL
- Defined in lib/canvas/offscreenCanvasAdapter.ts:138

writeImageToBytes

writeImageToBytes(image: GeoPackageImage, imageFormat: ImageType, compressionQuality?: number): Promise<Uint8Array>
Write image to bytes
Parameters
- image: GeoPackageImage
- imageFormat: ImageType
- Optional compressionQuality: number
Returns Promise<Uint8Array>
Implementation of CanvasAdapter.writeImageToBytes
- Defined in lib/canvas/offscreenCanvasAdapter.ts:163

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