Java Doc for GeographicImageReader.java in  » GIS » GeoTools-2.4.1 » org » geotools » image » io » Java Source Code / Java DocumentationJava Source Code and Java Documentation

More specifically, this class provides the following conveniences to implementors:

• Provides default GeographicImageReader.getNumImages and GeographicImageReader.getNumBands implementations, which return 1. This default behavior matches simple image formats like flat binary files or ASCII files. Those methods need to be overrided for more complex image formats.

• Provides GeographicImageReader.checkImageIndex and GeographicImageReader.checkBandIndex convenience methods. Those methods are invoked by most implementation of public methods. They perform their checks based on the informations provided by the above-cited GeographicImageReader.getNumImages and GeographicImageReader.getNumBands methods.

• Provides default implementations of GeographicImageReader.getImageTypes and GeographicImageReader.getRawImageType , which assume that only one is supported. The default image type is created from the informations provided by GeographicImageReader.getRawDataType and GeographicImageReader.getImageMetadata .

• Provides GeographicImageReader.getStreamMetadata and GeographicImageReader.getImageMetadata default implementations, which return null as authorized by the specification. Note that subclasses should consider returning GeographicMetadata instances.

The default implementation returns false in all cases, thus avoiding arbitrary choice.

The default Java implementation passed a null parameter.

The default implementation returns false in all cases, thus avoiding arbitrary choice. Subclasses can override this method with some arbitrary threashold, as in the example below:

 return unusedSpace >= 1024;
 

Implementations of the GeographicImageReader.read(int,ImageReadParam) method should invoke this method instead of GeographicImageReader.getDestination(ImageReadParam,Iterator,int,int) .
Parameters:
  imageIndex - The index of the image to be retrieved.
Parameters:
  parameters - The parameter given to the read method.
Parameters:
  width - The true width of the image or tile begin decoded.
Parameters:
  height - The true width of the image or tile being decoded.
Parameters:
  converters - If non-null, an array where to store the converters requiredfor converting decoded pixel data into stored pixel data. The buffered image to which decoded pixel data should be written.
throws:
  IOException - If an error occurs reading the format information from the input source.
See Also:   GeographicImageReader.getRawImageType(int,ImageReadParam,SampleConverter[])

Note that this method forces GeographicImageReader.ignoreMetadata to false for the time of (imageIndex) execution, because some image reader implementations need geographic metadata in order to infer a valid .
Parameters:
  imageIndex - The image index. The geographic metadata, or null if none.
throws:
  IOException - if an error occurs during reading.

Handling of negative integer values

• If this method returns DataBuffer.TYPE_SHORT , then the data will be stored "as is" without transformation. However the will have the maximal length allowed by 16 bits integers, with positive values in the [0 .. ] range and negative values wrapped in the [32768 .. 65535] range in two's complement binary form. The results is a color model consuming 256 kilobytes in every cases. The space not used by the [-23000 .. +23000] range (in the above example) is lost.

• If this method returns DataBuffer.TYPE_USHORT , then the data will be translated to the smallest strictly positive range that can holds the data ([1..46000] for the above example). Value 0 is reserved for missing data. The result is a smaller than the one used by untranslated data.

(imageIndex, , null);

1. The and the are extracted from the , if any.

2. If the given parameters argument is an instance of GeographicImageReadParam , then the user-supplied is fetched. Otherwise or if no palette name was explicitly set, then this method default to . The palette name will be used in order to (as RGB values) to be given to the .

3. If the is DataBuffer.TYPE_FLOATTYPE_FLOAT or DataBuffer.TYPE_DOUBLE TYPE_DOUBLE , then this method builds a suitable for the range fetched at step 1. The data are assumed geophysics values rather than some packed values. Consequently, the will replace no-data values by with no other changes.

4. Otherwise, if the is a unsigned integer type like DataBuffer.TYPE_BYTE TYPE_BYTE or DataBuffer.TYPE_USHORT TYPE_USHORT , then this method builds an (i.e. a palette backed by an ) with just the minimal needed for containing fully the range and the no-data values fetched at step 1. The data are assumed packed values rather than geophysics values. Consequently, the will be the except in the following cases:

   • The is outside the range allowed by the (e.g. the range of valid values contains negative integers). In this case, the sample converter will shift the values to a strictly positive range and replace no-data values by 0.
   • At least one is outside the range of values allowed by the . In this case, this method will try to only replace the no-data values by 0, without shifting the valid values if this shift can be avoided.
   • At least one is far away from the (for example 9999 while the range of valid values is [0..255]). The meaning of "far away" is determined by the GeographicImageReader.collapseNoDataValues collapseNoDataValues method.

5. Otherwise, if the is a signed integer type like DataBuffer.TYPE_SHORT TYPE_SHORT , then this method builds an with the maximal supported by the raw data type (note that this is memory expensive - typically 256 kilobytes). Negative values will be stored in their two's complement binary form in order to fit in the range of positive integers supported by the .

Overriding this method

int minimum = -2000; // minimal expected value
int maximum = +2300; // maximal expected value
int fillValue = -9999; // Value for missing data
String palette = "SST-Nasa";// Named set of RGB colors
converters[0] = (1 - minimum, fillValue);
return . (paletteName, maximum - minimum). ();

The default Java implementation passed a null parameter. This implementation passes the default parameter instead in order to improve consistency when a subclass overrides GeographicImageReader.getDefaultReadParam .
Parameters:
  imageIndex - the index of the image to be retrieved. the desired portion of the image.
throws:
  IllegalStateException - if the input source has not been set.
throws:
  IndexOutOfBoundsException - if the supplied index is out of bounds.
throws:
  IOException - if an error occurs during reading.

• If at least one has been , then the IIOReadWarningListener.warningOccurred warningOccurred method is invoked for each of them and the log record is not logged.
• Otherwise, the log record is sent to the "org.geotools.image.io" logger.