Package org.geotools.referencing.operation.builder

Class GridToEnvelopeMapper

Object
GridToEnvelopeMapper
public class GridToEnvelopeMapper extends Object
A helper class for building n-dimensional affine transform mapping grid ranges to envelopes. The affine transform will be computed automatically from the information specified by the setGridRange and setEnvelope methods, which are mandatory. All other setter methods are optional hints about the affine transform to be created. This builder is convenient when the following conditions are meet:

  • Pixels coordinates (usually (x,y) integer values inside the rectangle specified by the grid range) are expressed in some coordinate reference system known at compile time. This is often the case. For example the CRS attached to BufferedImage has always (column, row) axis, with the origin (0,0) in the upper left corner, and row values increasing down.

  • "Real world" coordinates (inside the envelope) are expressed in arbitrary horizontal coordinate reference system. Axis directions may be (North, West), or (East, North), etc..

In such case (and assuming that the image's CRS has the same characteristics than the BufferedImage's CRS described above):

  • swapXY shall be set to true if the "real world" axis order is (North, East) instead of (East, North). This axis swapping is necessary for mapping the (column, row) axis order associated to the image CRS.

  • In addition, the "real world" axis directions shall be reversed (by invoking reverseAxis(dimension)) if their direction is WEST (x axis) or NORTH (y axis), in order to get them oriented toward the EAST or SOUTH direction respectively. The later may seems unatural, but it reflects the fact that row values are increasing down in an BufferedImage's CRS.

Since:
2.3
Author:
Martin Desruisseaux (IRD)

  • Field Details

  • Constructor Details

    • GridToEnvelopeMapper

      public GridToEnvelopeMapper()
      Creates a new instance of GridToEnvelopeMapper.

    • GridToEnvelopeMapper

      public GridToEnvelopeMapper(GridEnvelope gridRange, Bounds userRange) throws MismatchedDimensionException
      Creates a new instance for the specified grid range and envelope.
      Parameters:
      gridRange - The valid coordinate range of a grid coverage.
      userRange - The corresponding coordinate range in user coordinate. This envelope must contains entirely all pixels, i.e. the envelope's upper left corner must coincide with the upper left corner of the first pixel and the envelope's lower right corner must coincide with the lower right corner of the last pixel.
      Throws:
      MismatchedDimensionException - if the grid range and the envelope doesn't have consistent dimensions.

  • Method Details

    • getPixelAnchor

      public PixelInCell getPixelAnchor()
      Returns whatever the grid range maps pixel center or pixel corner. The former is OGC convention while the later is Java2D/JAI convention. The default is cell center (OGC convention).
      Returns:
      Whatever the grid range maps pixel center or corner.
      Since:
      2.5

    • setPixelAnchor

      public void setPixelAnchor(PixelInCell anchor)
      Sets whatever the grid range maps pixel center or pixel corner. The former is OGC convention while the later is Java2D/JAI convention.
      Parameters:
      anchor - Whatever the grid range maps pixel center or corner.
      Since:
      2.5

    • getGridRange

      public GridEnvelope getGridRange() throws IllegalStateException
      Returns the grid range.
      Returns:
      The grid range.
      Throws:
      IllegalStateException - if the grid range has not yet been defined.

    • setGridRange

      public void setGridRange(GridEnvelope gridRange)
      Sets the grid range.
      Parameters:
      gridRange - The new grid range.

    • getEnvelope

      public Bounds getEnvelope() throws IllegalStateException
      Returns the envelope. For performance reason, this method do not clone the envelope. So the returned object should not be modified.
      Returns:
      The envelope.
      Throws:
      IllegalStateException - if the envelope has not yet been defined.

    • setEnvelope

      public void setEnvelope(Bounds envelope)
      Sets the envelope. This method do not clone the specified envelope, so it should not be modified after this method has been invoked.
      Parameters:
      envelope - The new envelope.

    • getSwapXY

      public boolean getSwapXY()
      Returns true if the two first axis should be interchanged. If isAutomatic(SWAP_XY) returns true (which is the default), then this method make the following assumptions:

      • Axis order in the grid range matches exactly axis order in the envelope, except for the special case described in the next point. In other words, if axis order in the underlying image is (column, row) (which is the case for a majority of images), then the envelope should probably have a (longitude, latitude) or (easting, northing) axis order.

      • An exception to the above rule applies for CRS using exactly the following axis order: (NORTH|SOUTH, EAST|WEST). An example of such CRS is EPSG:4326. In this particular case, this method will returns true, thus suggesting to interchange the (y,x) axis for such CRS.

      Returns:
      true if the two first axis should be interchanged.

    • setSwapXY

      public void setSwapXY(boolean swapXY)
      Tells if the two first axis should be interchanged. Invoking this method force isAutomatic(SWAP_XY) to false.
      Parameters:
      swapXY - true if the two first axis should be interchanged.

    • getReverseAxis

      public boolean[] getReverseAxis()
      Returns which (if any) axis in user space (not grid space) should have their direction reversed. If isAutomatic(REVERSE_AXIS) returns true (which is the default), then this method make the following assumptions:

      • Axis should be reverted if needed in order to point toward their "absolute" direction.
      • An exception to the above rule is the second axis in grid space, which is assumed to be the y axis on output device (usually the screen). This axis is reversed again in order to match the bottom direction often used with such devices.
      Returns:
      The reversal state of each axis, or null if unspecified.

    • setReverseAxis

      public void setReverseAxis(boolean[] reverse)
      Set which (if any) axis in user space (not grid space) should have their direction reversed. Invoking this method force isAutomatic(REVERSE_AXIS) to false.
      Parameters:
      reverse - The reversal state of each axis. A null value means to reverse no axis.

    • reverseAxis

      public void reverseAxis(int dimension)
      Reverses a single axis in user space. Invoking this methods n time is equivalent to creating a boolean reverse array of the appropriate length, setting reverse[dimension] = true for the n axis to be reversed, and invoke setReverseAxis(reverse).
      Parameters:
      dimension - The index of the axis to reverse.

    • isAutomatic

      public boolean isAutomatic(int mask)
      Returns true if all properties designed by the specified bit mask will be computed automatically.
      Parameters:
      mask - Any combination of REVERSE_AXIS or SWAP_XY.
      Returns:
      true if all properties given by the mask will be computed automatically.

    • setAutomatic

      public void setAutomatic(int mask)
      Set all properties designed by the specified bit mask as automatic. Their value will be computed automatically by the corresponding methods (e.g. getReverseAxis(), getSwapXY()). By default, all properties are automatic.
      Parameters:
      mask - Any combination of REVERSE_AXIS or SWAP_XY.

    • createTransform

      public MathTransform createTransform() throws IllegalStateException
      Creates a math transform using the information provided by setter methods.
      Returns:
      The math transform.
      Throws:
      IllegalStateException - if the grid range or the envelope were not set.

    • createAffineTransform

      public AffineTransform createAffineTransform() throws IllegalStateException
      Returns the math transform as a two-dimensional affine transform.
      Returns:
      The math transform as a two-dimensional affine transform.
      Throws:
      IllegalStateException - if the math transform is not of the appropriate type.