Class BufferedGridCoverage


public class BufferedGridCoverage extends GridCoverage
Basic access to grid data values backed by a n-dimensional DataBuffer. Those data can be shown as an untiled RenderedImage. Images are created when render(GridExtent) is invoked instead of at construction time. This delayed construction makes this class better suited to n-dimensional grids since those grids cannot be wrapped into a single RenderedImage.
Comparison with alternatives: this class expects all data to reside in-memory and does not support tiling. Pixels are stored in a row-major fashion with all bands in a single array or one array per band. By contrast, GridCoverage2D allows more flexibility in data layout and supports tiling with data loaded or computed on-the-fly, but is restricted to two-dimensional images (which may be slices in a n-dimensional grid).
The number of bands is determined by the number of SampleDimensions specified at construction time. The number of banks is either 1 or the number of bands.
  • If the number of banks is 1, all data are packed in a single array with band indices varying fastest, then column indices (x), then row indices (y), then other dimensions.
  • If the number of banks is greater than 1, then each band is stored in a separated array. In each array, sample values are stored with column indices (x) varying fastest, then row indices (y), then other dimensions. In the two-dimensional case, this layout is also known as row-major.
The number of cells in each dimension is specified by the GridExtent of the geometry given at construction time. By default the extent size in the two first dimensions will define the image width and height, but different dimensions may be used depending on which dimensions are identified as the subspace dimensions.
Since:
1.1
Version:
1.3
  • Field Details

    • data

      protected final DataBuffer data
      The sample values, potentially multi-banded. The bands may be stored either in a single bank (pixel interleaved image) or in different banks (banded image). This class detects automatically which of those two sample models is used when render(GridExtent) is invoked.

      Sample values in this buffer shall not be packed.

    • cachedRenderings

      private final Cache<GridExtent,RenderedImage> cachedRenderings
      Cache of rendered images produced by calls to render(GridExtent). Those images are cached because, even if they are cheap to create, they may become the source of a chain of operations for statistics, image resampling, etc. Caching the source image preserves not only the RenderedImage instance created by the render(GridExtent) method, but also the chain of operations potentially derived from that image.

      Usage

      Implementation of render(GridExtent) method can be like below:
  • Constructor Details

    • BufferedGridCoverage

      public BufferedGridCoverage(GridGeometry domain, List<? extends SampleDimension> range, DataBuffer data)
      Constructs a grid coverage using the specified grid geometry, sample dimensions and data buffer. This method stores the given buffer by reference (no copy). The bands in the given buffer can be stored either in a single bank (pixel interleaved image) or in different banks (banded image). This class detects automatically which of those two sample models is used (see class javadoc for more information).

      Note that DataBuffer does not contain any information about image size. Consequently, render(GridExtent) depends on the domain GridExtent, which must be accurate. If the extent size does not reflect accurately the image size, then the image will not be rendered properly.

      Parameters:
      domain - the grid extent, CRS and conversion from cell indices to CRS.
      range - sample dimensions for each image band.
      data - the sample values, potentially multi-banded.
      Throws:
      NullPointerException - if an argument is null.
      IllegalArgumentException - if the data buffer has an incompatible number of banks.
      IllegalGridGeometryException - if the grid extent is larger than the data buffer capacity.
      ArithmeticException - if the number of cells is larger than 64 bits integer capacity.
    • BufferedGridCoverage

      public BufferedGridCoverage(GridGeometry grid, List<? extends SampleDimension> bands, int dataType)
      Constructs a grid coverage using the specified grid geometry, sample dimensions and data type. This constructor creates a single-bank DataBuffer (pixel interleaved sample model) with all sample values initialized to zero.
      Parameters:
      grid - the grid extent, CRS and conversion from cell indices to CRS.
      bands - sample dimensions for each image band.
      dataType - one of DataBuffer.TYPE_* constants, the native data type used to store the coverage values.
      Throws:
      ArithmeticException - if the grid size is too large.
  • Method Details

    • getSampleCount

      private static long getSampleCount(GridExtent extent, long nbSamples)
      Returns the number of cells in the given extent multiplied by the number of bands.
      Parameters:
      extent - the extent for which to get the number of cells.
      nbSamples - number of bands.
      Returns:
      number of cells multiplied by the number of bands.
      Throws:
      ArithmeticException - if the number of samples exceeds 64-bits integer capacity.
    • getBandType

      final DataType getBandType()
      Returns the constant identifying the primitive type used for storing sample values.
      Overrides:
      getBandType in class GridCoverage
    • evaluator

      public GridCoverage.Evaluator evaluator()
      Creates a new function for computing or interpolating sample values at given locations.

      Multi-threading

      Evaluators are not thread-safe. For computing sample values concurrently, a new GridCoverage.Evaluator instance should be created for each thread.
      Overrides:
      evaluator in class GridCoverage
      Returns:
      a new function for computing or interpolating sample values.
    • render

      public RenderedImage render(GridExtent sliceExtent)
      Returns a two-dimensional slice of grid data as a rendered image. This method returns a view; sample values are not copied.

      The default implementation prepares an ImageRenderer, then invokes configure(ImageRenderer) for allowing subclasses to complete the renderer configuration before to create the image.

      Specified by:
      render in class GridCoverage
      Parameters:
      sliceExtent - a subspace of this grid coverage extent where all dimensions except two have a size of 1 cell. May be null if this grid coverage has only two dimensions with a size greater than 1 cell.
      Returns:
      the grid slice as a rendered image.
    • configure

      protected void configure(ImageRenderer renderer)
      Invoked by the default implementation of render(GridExtent) for completing the renderer configuration before to create an image. The default implementation does nothing.

      Some example of methods that subclasses may want to use are:

      Parameters:
      renderer - the renderer to configure before to create an image.
      Since:
      1.3