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Class LuminanceSource

The purpose of this class hierarchy is to abstract different bitmap implementations across platforms into a standard interface for requesting greyscale luminance values. The interface only provides immutable methods; therefore crop and rotation create copies. This is to ensure that one Reader does not modify the original luminance source and leave it in an unknown state for other Readers in the chain.

author

dswitkin@google.com (Daniel Switkin)

Hierarchy

Index

Constructors

Protected constructor

Properties

Private height

height: number

Private width

width: number

Methods

crop

  • crop(left: number, top: number, width: number, height: number): LuminanceSource
  • Returns a new object with cropped image data. Implementations may keep a reference to the original data rather than a copy. Only callable if isCropSupported() is true.

    Parameters

    • left: number

      The left coordinate, which must be in [0,getWidth())

    • top: number

      The top coordinate, which must be in [0,getHeight())

    • width: number

      The width of the rectangle to crop.

    • height: number

      The height of the rectangle to crop.

    Returns LuminanceSource

    A cropped version of this object.

getHeight

  • getHeight(): number

Abstract getMatrix

  • getMatrix(): Uint8ClampedArray
  • Fetches luminance data for the underlying bitmap. Values should be fetched using: {@code int luminance = array[y * width + x] & 0xff}

    Returns Uint8ClampedArray

    A row-major 2D array of luminance values. Do not use result.length as it may be larger than width * height bytes on some platforms. Do not modify the contents of the result.

Abstract getRow

  • getRow(y: number, row?: Uint8ClampedArray): Uint8ClampedArray
  • Fetches one row of luminance data from the underlying platform's bitmap. Values range from 0 (black) to 255 (white). Because Java does not have an unsigned byte type, callers will have to bitwise and with 0xff for each value. It is preferable for implementations of this method to only fetch this row rather than the whole image, since no 2D Readers may be installed and getMatrix() may never be called.

    Parameters

    • y: number

      The row to fetch, which must be in [0,getHeight())

    • Optional row: Uint8ClampedArray

      An optional preallocated array. If null or too small, it will be ignored. Always use the returned object, and ignore the .length of the array.

    Returns Uint8ClampedArray

    An array containing the luminance data.

getWidth

  • getWidth(): number

Abstract invert

isCropSupported

  • isCropSupported(): boolean

isRotateSupported

  • isRotateSupported(): boolean

rotateCounterClockwise

  • Returns a new object with rotated image data by 90 degrees counterclockwise. Only callable if {@link #isRotateSupported()} is true.

    Returns LuminanceSource

    A rotated version of this object.

rotateCounterClockwise45

  • Returns a new object with rotated image data by 45 degrees counterclockwise. Only callable if {@link #isRotateSupported()} is true.

    Returns LuminanceSource

    A rotated version of this object.

toString

  • toString(): string

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