User's Guide

BROWSE

Convert an AVHRR LAS image into a browse image file

Function:

Converts the specified AVHRR LAS image into a browse image file containing 408-byte records. The first record is a header containing the scene ID, minimum and maximum pixel values, number of lines and samples, channels selected, and latitude/ longitude coordinates of the scene's corners. The subseqent records contain byte image data. The browse image possibly has a lower resolution than the origonal image and is used by other systems as a reference.

Parameters:

IN
Input image. The name of the AVHRR LAS image from which a browse image is to be created. A window and/or band specification may be included as part of the input name. The image may contain BYTE or INTEGER*2 data.

OUT
Output image. The name(s) of the browse image(s) to be created. The number of images specified in OUT must be either one or the number of bands in IN. If one output image is specified, all bands of IN will be written sequentially to OUT. If multiple output images are specified, each will contain one band of IN.

Examples:

  1. LAS> browse in=descend out=br1

    All bands of the AVHRR LAS image DESCEND are written sequentially to a browse image named BR1. If DESCEND is a GAC image, the entire image will be written to a browse image. If DESCEND is a LAC or HRPT image, every fourth line and fifth sample will be written to the browse image.

  2. LAS> browse in="descend(1 1 100 100:3 4 5)" out=br2

    Bands three, four, and five of the AVHRR LAS image DESCEND are sequentially written to a browse image named BR2. If DESCEND is a GAC image, 100 lines and 100 samples of each band will be written to the browse image. If DESCEND is a LAC or HRPT image, 25 lines and 20 samples will be written to the browse image.

  3. LAS> browse in="descend(:3 4 5)" out=(br3 br4 br5)

    Bands three, four, and five of the AVHRR LAS image DESCEND are written to browse images BR3, BR4, and BR5, respectively.

Description/Algorithm:

BROWSE converts image files used in the LAS system to browse image files that contain BYTE image data with one header record. The user may specify a subset of bands and/or a window to be processed. The input image may contain BYTE or INTEGER*2 data. The pixels of a BYTE image will be written directly to the browse image, while an INTEGER*2 image will have its pixel values scaled to the range of BYTE data. All bands of the output image may be written to the same file in band sequential format, or they may be written to separate image files. If IN is a GAC image, the specified windows and/or bands will be written to the browse image. If IN is LAC or HRPT data, then every fifth and fourth line are used to create a browse image with the same resolution as a GAC image.

Nonfatal Error Message:

    None.

Fatal Error Messages:

  1. [browse-alloc] Error allocating dynamic memory

    An error occurred while trying to free dynamically allocated memory. This additional memory was necessary for further processing. Contact the system manager if the problem persists.

  2. [browse-dtype] Invalid input image data type

    The input image has an invalid data type. IN must be of type BYTE or I*2.

  3. [browse-fatal] Fatal error encountered

    A fatal error was encountered during processing. The preceding message describes the error.

  4. [browse-onames] Invalid number of output files specified

    OUT had an invalid number of output files specified. The number of images specified in OUT must be either one or the number of bands in IN. If one output image is specified, all bands of IN will be written sequentially to OUT. If multiple output images are specified, each will contain one band of IN.

  5. [browse-outopen] Error opening output image

    An error occurred while trying to open the output image. Check to ensure an image of this name doesn't already exist, that there is sufficient disk space to hold the browse image, and that you are allowed to write to the specified directory.

  6. [browse-reset] Error resetting the browse file

    An error occurred while resetting to the header record of the browse image file. Contact the system administrator, as this error indicates a problem with the file descriptor.

  7. [browse-write] Error writing <XXXX>

    An error occurred while trying to write to the output image. Make sure you have write permission in the current working directory.

User Notes:

  1. Browse images contain BYTE data and may be transferred to any system without byte-swapping the data.

  2. IN may contain BYTE or INTEGER*2 data. The pixels of a BYTE image will be written directly to the browse image, while an INTEGER*2 image will have its pixel values scaled to the range of BYTE data.

  3. If IN is LAC or HRPT data, the image is subsampled at every fifth sample and fourth line. This subsampling will create a browse image with the same resolution as a GAC image.