PGMB Files
Portable Gray Map (binary)

PGMB files are the binary form of the portable gray map PGM format. It is a simple gray map description. The definition is as follows:

• the typical file extension is ".pgm", but an extension of ".pnm" is also occasionally used.
• A "magic number" for identifying the file type. A binary PGMB file's magic number is the two characters "P5".
• Whitespace (blanks, TABs, CRs, LFs).
• A width, formatted as ASCII characters in decimal.
• Whitespace.
• A height, again in ASCII decimal.
• Whitespace.
• The maximum gray value, MAXVAL, again in ASCII decimal. MAXVAL must be between 0 and 255.
• A single character of whitespace, typically a newline;
• Width * height gray values, each stored as a plain byte, between 0 and the specified maximum value, separated by whitespace, starting at the top-left corner of the graymap, proceeding in normal English reading order. A value of 0 means black, and the maximum value means white.

PGMB File Characteristics:

• binary
• Gray scale only
• 2D
• No compression
• 1 image

Related Data and Programs:

The PBMB data directory describes binary Portable Bit Map files.

The PGMA data directory describes ASCII Portable Gray Map files.

The PPMB data directory describes binary Portable Pixel Map files.

Reference:

1. the NETPBM homepage.

Programs and routines to read a PGMB file:

• MATLAB can read a PGMB file with a command like A=imread('file','PGM').
• pbmlib, FORTRAN90 routines.
• pgmb_io C++ routines.
• The Visual Toolkit routine vtkPNMReader can read a binary PGM file into VTK.

Programs and routines to write a PGMB file:

• The gnuplot command "set terminal pbm gray".
• MATHEMATICA includes an Export[filename,object] command that can save a graphics object as a binary PGM file.
• MATLAB can write a PGMB file with a command like imwrite(a,'filename','PGM').
• pbmlib, FORTRAN90 routines.
• pgmb_io C++ routines.
• The Visual Toolkit routine vtkPNMWriter can write a VTK image to a binary PGM file.

Programs to view a PGMB file:

• The AVS module read_any_image can read a PGMB file;
• GIMP, the GNU Image Manipulation Program, can read a PGMB file.
• The ImageVision program imgview can display a PGMB file.
• MATLAB can display a PGMB file, once it is read in, with a command like image(A).
• xv can display a PGMB file.

Programs to convert a PGMB file to another format:

• cjpeg converts a PGM to JPEG format.
• The ImageMagick, program convert can convert a PGMB file to BMP, CGM, EPS, FIG, FITS, GIF, JPG, PBM, PDF, PGM, PNG, PNM, PPM, PS, RGB, TIF, XBM or XPM format.
• GIMP, the GNU Image Manipulation Program, can read a PGMB file and write out a copy in a variety of formats.
• PGMB_TO_PGMA is a C++ program which can convert a PGMB file to PGMA format.
• The NETPBM program PGMTOFITS converts a PGMB file to FITS format.
• xv can read a PGMB file and write out a copy in BMP, FIT, GIF, JPG, PBM, PPM, RGB or TIF format.

Programs to convert a file to PGMB format:

• The ImageMagick, program convert can convert a BMP, CGM, EPS, FIG, FITS, GIF, JPG, PBM, PDF, PGM, PNG, PNM, PPM, PS, RGB, TIF, XBM or XPM file to PGMB format.
• djpeg converts a JPEG file to PGM format.
• GIMP, the GNU Image Manipulation Program, can read a file in a variety of formats, and write it out as a PGMB file.
• The NETPBM program FITSTOPGM converts a FITS file to PGMB format.
• PGMA_TO_PGMB is a C++ program which can convert a PGMA file to PGMB format.
• xv can read a file in a BMP, FIT, GIF, JPG, PBM, PPM, RGB or TIF format, and write it out as a PGMB file.

Sample PGMB Files:

• baboon.pgmb, a baboon.
• barbara.pgmb.
• lena.pgmb.
• pbmlib.pgmb, a file created by PBMLIB.

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