MATLAB Function Reference

hdfinfo

Return information about an HDF or HDF-EOS file

Syntax

• S = hdfinfo(filename)
  S = hdfinfo(filename,mode)
  

Description

S = hdfinfo(filename) returns a structure, S, whose fields contain information about the contents of an HDF or HDF-EOS file. filename is a string that specifies the name of the HDF file.

S = hdfinfo(filename,mode) reads the file as an HDF file, if mode is 'hdf', or as an HDF-EOS file, if mode is 'eos'. If mode is 'eos', only HDF-EOS data objects are queried. To retrieve information on the entire contents of a file containing both HDF and HDF-EOS objects, mode must be 'hdf'.

Note    hdfinfo can be used on version 4.x HDF files or version 2.x HDF-EOS files.

The set of fields in the returned structure, S, depends on the individual file. Fields that may be present in the S structure are shown in the following table.

HDF Object Fields

Mode	Fieldname	Description	Return Type
HDF	Attributes	Attributes of the data set	Structure array
	Description	Annotation description	Cell array
	Filename	Name of the file	String
	Label	Annotation label	Cell array
	Raster8	Description of 8-bit raster images	Structure array
	Raster24	Description of 24-bit raster images	Structure array
	SDS	Description of scientific data sets	Structure array
	Vdata	Description of Vdata sets	Structure array
	Vgroup	Description of Vgroups	Structure array
EOS	Filename	Name of the file	String
	Grid	Grid data	Structure array
	Point	Point data	Structure array
	Swath	Swath data	Structure array

Those fields in the table above that contain structure arrays are further described in the tables shown below.

Fields Common to Returned Structure Arrays

Structure arrays returned by hdfinfo contain some common fields. These are shown in the table below. Not all structure arrays will contain all of these fields.

Common Fields

Fieldname	Description	Data Type
Attributes	Data set attributes. Contains fields Name and Value	Structure array
Description	Annotation description	Cell array
Filename	Name of the file	String
Label	Annotation label	Cell array
Name	Name of the data set	String
Rank	Number of dimensions of the data set	Double
Ref	Data set reference number	Double
Type	Type of HDF or HDF-EOS object	String

Fields Specific to Certain Structures

Structure arrays returned by hdfinfo also contain fields that are unique to each structure. These are shown in the tables below.

Fields of the Attribute Structure

Fieldname	Description	Data Type
Name	Attribute name	String
Value	Attribute value or description	Numeric or string

Fields of the Raster8 and Raster24 Structures

Fieldname	Description	Data Type
HasPalette	1 (true) if the image has an associated palette, otherwise 0 (false). (8-bit only)	Logical
Height	Height of the image, in pixels	Number
Interlace	Interlace mode of the image (24-bit only)	String
Name	Name of the image	String
Width	Width of the image, in pixels	Number

Fields of the SDS Structure

Fieldname	Description	Data Type
DataType	Data precision	String
Dims	Dimensions of the data set. Contains fields: Name, DataType, Size, Scale, and Attributes. Scale is an array of numbers to place along the dimension and demarcate intervals in the data set	Structure array
Index	Index of the SDS	Number

Fields of the Vdata Structure

Fieldname	Description	Data Type
DataAttributes	Attributes of the entire data set. Contains fields: Name and Value	Structure array
Class	Class name of the data set	String
Fields	Fields of the Vdata. Contains fields: Name and Attributes	Structure array
NumRecords	Number of data set records.	Double
IsAttribute	1 (true) if Vdata is an attribute, otherwise 0 (false).	Logical

Fields of the Vgroup Structure

Fieldname	Description	Data Type
Class	Class name of the data set.	String
Raster8	Description of the 8-bit raster image.	Structure array
Raster24	Description of the 24-bit raster image.	Structure array
SDS	Description of the Scientific Data sets.	Structure array
Tag	Tag of this Vgroup.	Number
Vdata	Description of the Vdata sets.	Structure array
Vgroup	Description of the Vgroups.	Structure array

Fields of the Grid Structure

Fieldname	Description	Data Type
Columns	Number of columns in the grid.	Number
DataFields	Description of the data fields in each Grid field of the grid. Contains fields: Name, Rank, Dims, NumberType, FillValue, and TileDims.	Structure array
LowerRight	Lower right corner location, in meters.	Number
Origin Code	Origin code for the grid.	Number
PixRegCode	Pixel registration code.	Number
Projection	Projection code, zone code, sphere code, and projection parameters of the grid. Contains fields: ProjCode, ZoneCode, SphereCode, and ProjParam.	Structure
Rows	Number of rows in the grid.	Number
UpperLeft	Upper left corner location, in meters.	Number

Fields of the Point Structure

Fieldname	Description	Data Type
Level	Description of each level of the point. Contains fields: Name, NumRecords, FieldNames, DataType, and Index.	Structure

Fields of the Swath Structure

Fieldname	Description	Data Type
DataFields	Data fields in the swath. Contains fields: Name, Rank, Dims, NumberType, and FillValue.	Structure array
GeolocationFields	Geolocation fields in the swath. Contains fields: Name, Rank, Dims, NumberType, and FillValue.	Structure array
IdxMapInfo	Relationship between indexed elements of the geolocation mapping. Contains fields: Map, and Size.	Structure
MapInfo	Relationship between data and geolocation fields. Contains fields: Map, Offset, and Increment.	Structure

Examples

To retrieve information about the file, example.hdf

• fileinfo = hdfinfo('example.hdf')
  
  fileinfo = 
      Filename: 'example.hdf'
           SDS: [1x1 struct]
         Vdata: [1x1 struct]
  

And to retrieve information from this about the scientific data set in example.hdf

• sds_info = fileinfo.SDS
  
  sds_info = 
         Filename: 'example.hdf'
             Type: 'Scientific Data Set'
             Name: 'Example SDS'
             Rank: 2
         DataType: 'int16'
       Attributes: []
             Dims: [2x1 struct]
            Label: {}
      Description: {}
            Index: 0
  

See Also

hdfread, hdf

hdf

hdfread