Routines (alphabetical) > Routines: Q > QUERY_JPEG2000

# QUERY_JPEG2000

The QUERY_JPEG2000 function allows you to obtain information about a JPEG2000 image file without having to read the file. It is a wrapper around the IDLffJPEG2000 object interface that presents JPEG2000 image loading in a way familiar to users of the QUERY_* image routines. (See QUERY_* Routines for more information.) However this function is not as efficient as the object interface and the object interface should be used whenever possible. See IDLffJPEG2000 for information about the object interface.

## Example

For a relevant example, see READ_JPEG2000.

## Syntax

Result = QUERY_JPEG2000(Filename [, Info] )

## Return Value

This routine returns a long integer with the value of 1 if the query was successful (and the file type was correct) or 0 on failure.

## Arguments

### Filename

A scalar string containing the full path and filename of the JPEG2000 file to query.

### Info

Returns an anonymous structure containing information about the image in the file. The Info.TYPE field will return the value 'JPEG2000'.

Note: See General Query * Routine Info Structures for detailed structure information.

In addition to the standard structure fields, the JPEG2000 query structure contains the following additional fields:

Field | IDL Data Type | Description
N_LAYERS | Long | The number of quality layers.
N_LEVELS | Long | The number of wavelet decomposition levels.
OFFSET | Two-element vector | The X and Y offsets for all image components.

## Keywords

None.

## Version History

6.1 | Introduced

## See Also

QUERY_* Routines, READ_JPEG2000, WRITE_JPEG2000