Package org.apache.sis.coverage.grid

Class PixelTranslation

  • All Implemented Interfaces:
    Serializable
    public final class PixelTranslation
extends Static
implements Serializable
    The translation to apply for different values of Pixel­Orientation or Pixel­In­Cell. The translation are returned by a call to one of the following static methods: This class provides also a few translate(…) convenience methods, which apply the translation on a given Math­Transform instance.
    Example: if the following code snippet, grid­To­CRS is an Affine­Transform from grid cell coordinates (typically pixel coordinates) to some arbitrary CRS coordinates. In this example, the transform maps pixels center, while the upper left corner is desired. This code will switch the affine transform from the pixel center to upper left corner convention: 
    final AffineTransform  gridToCRS = ...;
final PixelOrientation current   = PixelOrientation.CENTER;
final PixelOrientation desired   = PixelOrientation.UPPER_LEFT;

// Switch the transform from 'current' to 'desired' convention.
final PixelTranslation source = getPixelTranslation(current);
final PixelTranslation target = getPixelTranslation(desired);
gridToCRS.translate(target.dx - source.dx,
                    target.dy - source.dy);
    Since:
    1.0
    See Also:
    Pixel­In­Cell, Pixel­Orientation, Serialized Form

    Defined in the sis-feature module

    • Field Detail

      • dx

        public final double dx
        The translation among the x axis relative to pixel center. The value is typically −½, 0 or +½.

      • dy

        public final double dy
        The translation among the y axis relative to pixel center. The value is typically −½, 0 or +½.

    • Method Detail

      • getPixelOrientation

        public static PixelOrientation getPixelOrientation​(PixelInCell anchor)
        Returns the pixel orientation which is equivalent to the given Pixel­In­Cell code. This equivalence can be used for converting n-dimensional parameters to the more specific two-dimensional case. This method implements the following mapping:
        Pixel orientation equivalences
        Pixel in cellPixel orientation
        CELL_CENTERCENTER
        CELL_CORNERUPPER_LEFT
        nullnull
        Parameters:
        anchor - the Pixel­In­Cell code, or null.
        Returns:
        the corresponding pixel orientation, or null if the argument was null.
        Throws:
        Illegal­Argument­Exception - if the given anchor is not a known code list value.

      • getPixelTranslation

        public static double getPixelTranslation​(PixelInCell anchor)
        Returns the position relative to the cell center. This method is typically used for n-dimensional grids, where the number of dimension is unknown. The translation is determined from the following table, with the same value applied to all dimensions:
        Translations
        Pixel in celloffset
        CELL_CENTER 0.0
        CELL_CORNER-0.5
        Parameters:
        anchor - the "pixel in cell" value.
        Returns:
        the translation for the given "pixel in cell" value.
        Throws:
        Illegal­Argument­Exception - if the given anchor is not a known code list value.

      • getPixelTranslation

        public static PixelTranslation getPixelTranslation​(PixelOrientation anchor)
        Returns the specified position relative to the pixel center. This method can be used for grid restricted to 2 dimensions. The translation vector is determined from the following table:
        Translations
        Pixel orientation dx dy
        CENTER  0.0 0.0
        UPPER_LEFT -0.5-0.5
        UPPER_RIGHT+0.5-0.5
        LOWER_LEFT -0.5+0.5
        LOWER_RIGHT+0.5+0.5
        Parameters:
        anchor - the pixel orientation.
        Returns:
        the position relative to the pixel center.
        Throws:
        Illegal­Argument­Exception - if the given anchor is not a known code list value.

      • translate

        public static MathTransform translate​(MathTransform gridToCRS,
                                      PixelInCell current,
                                      PixelInCell desired)
        Converts a math transform from a "pixel in cell" convention to another "pixel in cell" convention. This method concatenates −½, 0 or +½ translations on all dimensions before the given transform. If the two given conventions are the same, then this method returns the given transform unchanged.
        Example: if a given grid­To­CRS transform was mapping the cell corner to "real world" coordinates, then a call to translate(grid­To­CRS, CELL_CORNER, CELL_CENTER) will return a new transform performing the following steps: first convert grid coordinates from cell center convention (desired) to cell corner convention (current), then concatenate the given grid­To­CRS transform which was designed for the cell corner convention. The above-cited cell center → cell corner conversion is done by translating the grid coordinates by +½, because the grid coordinates (0,0) relative to cell center is (½,½) relative to cell corner.
        If the given grid­To­CRS is null, then this method ignores all other arguments and returns null. Otherwise current and desired arguments must be non-null.
        Parameters:
        grid­To­CRS - a math transform from pixel coordinates to any CRS, or null.
        current - the pixel orientation of the given grid­To­CRS transform.
        desired - the pixel orientation of the desired transform.
        Returns:
        the translation from current to desired, or null if grid­To­CRS was null.
        Throws:
        Illegal­Argument­Exception - if current or desired is not a known code list value.

      • translate

        public static MathTransform translate​(MathTransform gridToCRS,
                                      PixelOrientation current,
                                      PixelOrientation desired,
                                      int xDimension,
                                      int yDimension)
        Converts a math transform from a "pixel orientation" convention to another "pixel orientation" convention. This method concatenates −½, 0 or +½ translations on two dimensions before the given transform. The given transform can have any number of input and output dimensions, but only two of them will be converted.
        Example: if a given grid­To­CRS transform was mapping the upper-left corner to "real world" coordinates, then a call to translate(grid­To­CRS, UPPER_LEFT, CENTER, 0, 1) will return a new transform translating grid coordinates by +0.5 before to apply the given grid­To­CRS transform. See example in above translate method for more details.
        If the given grid­To­CRS is null, then this method ignores all other arguments and returns null. Otherwise current and desired arguments must be non-null.
        Parameters:
        grid­To­CRS - a math transform from pixel coordinates to any CRS, or null.
        current - the pixel orientation of the given grid­To­CRS transform.
        desired - the pixel orientation of the desired transform.
        x­Dimension - the dimension of x coordinates (pixel columns). Often 0.
        y­Dimension - the dimension of y coordinates (pixel rows). Often 1.
        Returns:
        the translation from current to desired, or null if grid­To­CRS was null.
        Throws:
        Illegal­Argument­Exception - if current or desired is not a known code list value.

      • toString

        public String toString()
        Returns a string representation of this pixel translation.
        Overrides:
        to­String in class Object