public class LocalizationGrid extends Object
MathTransform2D
backed by a grid of localization. A grid of
localization is a twodimensional array of coordinate points. The grid size is width
× height
. Input coordinates are (i,j) index
in the grid, where i must be in the range [0..width1]
and j in the
range [0..height1]
inclusive. Output coordinates are the values stored in the grid of
localization at the specified index.
The LocalizationGrid
class is usefull when the "grid to coordinate system" transform for a coverage is
not some kind of global mathematical relationship like an affine
transform. Instead, the "real world" coordinates are explicitly specified for each pixels. If
the real world coordinates are know only for some pixels at a fixed interval, then a
transformation can be constructed by the concatenation of an affine transform with a grid of
localization.
After a LocalizationGrid
object has been fully constructed (i.e. real world
coordinates have been specified for all grid cells), a transformation from grid coordinates to
"real world" coordinates can be obtained with the getMathTransform()
method. If this
transformation is close enough to an affine transform, then an instance of AffineTransform
is returned. Otherwise, a transform backed by the localization grid is returned.
The example below goes through the steps of constructing a coordinate reference system for a grid coverage from its grid of localization. This example assumes that the "real world" coordinates are longitudes and latitudes on the WGS84 ellipsoid.
// // Constructs a localization grid of size 10×10. // LocalizationGrid grid = new LocalizationGrid(10,10); for (int j=0; j<10; j++) { for (int i=0; i<10; i++) { double x = ...; // Set longitude here double y = ...; // Set latitude here grid.setLocalizationPoint(i,j,x,y); } } // // Constructs the grid coordinate reference system. degree is the polynomial // degree (e.g. 2) for a math transform that approximately map the grid of localization. // For a more accurate (but not always better) math transform backed by the whole grid, // invokes getMathTransform() instead, or use the special value of 0 for the degree // argument. // MathTransform2D realToGrid = grid.getPolynomialTransform(degree).inverse(); CoordinateReferenceSystem realCRS = DefaultGeographicCRS.WGS84; CoordinateReferenceSystem gridCRS = new DefaultDerivedCRS("The grid CRS", new DefaultOperationMethod(realToGrid), realCRS, // The target ("real world") CRS realToGrid, // How the grid CRS relates to the "real world" CRS DefaultCartesianCS.GRID); // // Constructs the grid coverage using the grid coordinate system (not the "real world" // one). It is usefull to display the coverage in its native CRS before we resample it. // Note that if the grid of localization does not define the geographic location for // all pixels, then we need to specify some affine transform in place of the call to // IdentityTransform. For example if the grid of localization defines the location of // 1 pixel, then skip 3, then defines the location of 1 pixel, etc., then the affine // transform should be AffineTransform.getScaleInstance(0.25, 0.25). // WritableRaster raster = RasterFactory.createBandedRaster(DataBuffer.TYPE_FLOAT, width, height, 1, null); for (int y=0; ysome_value); } } GridCoverageFactory factory = FactoryFinder.getGridCoverageFactory(null); GridCoverage coverage = factory.create("My grayscale coverage", raster, gridCRS, IdentityTransform.create(2), null, null, null, null, null); coverage.show(); // // Projects the coverage from its current 'gridCS' to the 'realCS'. If the grid of // localization was built from the orbit of some satellite, then the projected // coverage will tpypically have a curved aspect. // coverage = (Coverage2D) Operations.DEFAULT.resample(coverage, realCRS); coverage.show();
DerivedCRS
Constructor and Description 

LocalizationGrid(int width,
int height)
Constructs an initially empty localization grid.

Modifier and Type  Method and Description 

AffineTransform 
getAffineTransform()
Returns an affine transform for the whole grid.

Point2D 
getLocalizationPoint(Point source)
Returns the "real world" coordinates for the specified grid coordinates.

MathTransform2D 
getMathTransform()
Returns a math transform from grid to "real world" coordinates.

MathTransform2D 
getPolynomialTransform(int degree)
Returns a math transform from grid to "real world" coordinates using a polynomial fitting of
the specified degree.

Dimension 
getSize()
Returns the grid size.

boolean 
isMonotonic(boolean strict)
Returns
true if all coordinates in this grid are increasing or decreasing. 
boolean 
isNaN()
Returns
true if this localization grid contains at least one NaN value. 
void 
removeSingularities()
Makes sure that the grid doesn't contains identical consecutive ordinates.

void 
setLocalizationPoint(int sourceX,
int sourceY,
double targetX,
double targetY)
Set a point in this localization grid.

void 
setLocalizationPoint(Point source,
Point2D target)
Set a point in this localization grid.

void 
transform(AffineTransform transform,
Rectangle region)
Apply a transformation to every "real world" coordinate points in a subregion of this grid.

public LocalizationGrid(int width, int height)
(NaN,NaN)
.width
 Number of grid's columns.height
 Number of grid's rows.public Dimension getSize()
x_{input} = [0..width1]
and
y_{input} = [0..height1]
inclusive.public Point2D getLocalizationPoint(Point source)
getMathTransform()
instead.source
 The point in grid coordinates.IndexOutOfBoundsException
 If the source point is not in this grid's range.public void setLocalizationPoint(Point source, Point2D target)
source
 The point in grid coordinates.target
 The corresponding point in "real world" coordinates.IndexOutOfBoundsException
 If the source point is not in this grid's range.public void setLocalizationPoint(int sourceX, int sourceY, double targetX, double targetY)
sourceX
 x coordinates in grid coordinates, in the range [0..width1]
inclusive.sourceY
 y coordinates in grid coordinates. in the range [0..height1]
inclusive.targetX
 x coordinates in "real world" coordinates.targetY
 y coordinates in "real world" coordinates.IndexOutOfBoundsException
 If the source coordinates is not in this grid's range.public void transform(AffineTransform transform, Rectangle region)
transform
 The transform to apply.region
 The bounding rectangle (in grid coordinate) for region where to apply the
transform, or null
to transform the whole grid.public boolean isNaN()
true
if this localization grid contains at least one NaN
value.public boolean isMonotonic(boolean strict)
true
if all coordinates in this grid are increasing or decreasing. More
specifically, returns true
if the following conditions are meets:
strict
is true
, then coordinates must be strictly increasing or decreasing (i.e. equals value
are not accepted). NaN
values are always ignored.
strict
 true
to require strictly increasing or decreasing order, or false
to accept values that are equals.true
if coordinates are increasing or decreasing in the same direction for
all rows and columns.public void removeSingularities()
public AffineTransform getAffineTransform()
public MathTransform2D getPolynomialTransform(int degree)
degree
of 0 will returns the math transform backed by the whole grid. Greater values will use a
fitted polynomial (affine transform for degree 1, quadratic
transform for degree 2, cubic transform for degree 3, etc.).degree
 The polynomial degree for the fitting, or 0 for a transform backed by the whole
grid.public final MathTransform2D getMathTransform()
WarpGrid
while the previous methods return math
transforms backed by WarpPolynomial
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