PBMA Files
ASCII Portable Bit Map Graphics Files

PBMA is the ASCII version of the portable bitmap (PBM) format, a lowest common denominator monochrome (black and white) file format. It was originally designed to make it reasonable to mail bitmaps between different types of machines. Now it serves as the common language of a large family of bitmap conversion filters.

The definition is as follows:

• the typical file extension is ".pbm", but an extension of ".pnm" is also occasionally used.
• A "magic number" for identifying the file type. An ASCII PBM file's magic number is the two characters "P1".
• Whitespace (blanks, TABs, CRs, LFs).
• A width, formatted as ASCII characters in decimal.
• Whitespace.
• A height, again in ASCII decimal.
• Whitespace.
• Width * height bits, each either '1' or '0', starting at the top-left corner of the bitmap, proceeding in normal English reading order.

Example ASCII PBM file:

        P1
        # feep.ascii.pbm
        24 7
        0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
        0 1 1 1 1 0 0 1 1 1 1 0 0 1 1 1 1 0 0 1 1 1 1 0
        0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 1 0
        0 1 1 1 0 0 0 1 1 1 0 0 0 1 1 1 0 0 0 1 1 1 1 0
        0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0
        0 1 0 0 0 0 0 1 1 1 1 0 0 1 1 1 1 0 0 1 0 0 0 0
        0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
      

ASCII PBM File Characteristics:

• ASCII
• black and white
• 2D
• No compression
• 1 image

Licensing:

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Related Data and Programs:

PBMA_IO is a C++ library which handles the Portable Bit Map (ASCII) format.

PBMB, a data directory which contains examples of PBMB files, binary Portable Bit Map 2D graphics, black and white;

PBMLIB, a C library which reads or writes graphics files in the Portable Bit Map format;

PGMA, a data directory which contains examples of PGMA files, ASCII Portable Gray Map, 2D graphics;

PPMA, a data directory which contains examples of PPMA files, Portable Pixel Map (ASCII) 2D graphics, color;

Reference:

1. the NETPBM homepage.

Programs to create an ASCII PBM file:

• The gnuplot command "set terminal pbm monochrome".
• the mathematica command DISPLAY;

Programs and routines to read an ASCII PBM file:

• MATLAB can read an ASCII PBM file with a command like A=imread('file','PBM').
• PBMA_IO is a library of routines which can read an ASCII PBM file. PBMA_IO is available in a C++ version, a FORTRAN90 version, and a MATLAB version;
• The Visual Toolkit routine vtkPNMReader can read a PNM file into VTK.

Programs and routines to write an ASCII PBM file:

• MATLAB can write an ASCII PBM file with a command like imwrite(a,'filename','PBM').
• PBMA_IO is a library of routines which can write an ASCII PBM file. PBMA_IO is available in a C++ version, a FORTRAN90 version, and a MATLAB version;
• The Visual Toolkit routine vtkPNMWriter can write a VTK image to an ASCII PBM file.

Programs to view an ASCII PBM file:

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

Programs to convert an ASCII PBM file to another format:

• convert, a program supplied with ImageMagick, can convert an ASCII PBM 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 an ASCII PBM file and write out a copy in a variety of formats.
• PBMTOASCII, a program that is part of NETPBM, can read an ASCII PBM file and write out it out as ASCII graphics.
• xv can read an ASCII PBM file and write out a copy in BMP, FIT, GIF, JPG, PGM, PPM, RGB or TIF format.

Programs to convert a file to ASCII PBM format:

• convert, a program supplied with ImageMagick, can convert a BMP, CGM, EPS, FIG, FITS, GIF, JPG, PBM, PDF, PGM, PNG, PNM, PPM, PS, RGB, TIF, XBM or XPM file to ASCII PBM format. However, to force the ASCII format, you must include the switch "-compress none".
• GIMP, the GNU Image Manipulation Program, can read a file in a variety of formats, and write it out as an ASCII PBM file.
• xv can read a file in a BMP, FIT, GIF, JPG, PGM, PPM, RGB or TIF format, and write it out as an ASCII PBM file.

Sample ASCII PBM files:

All the filenames here include the extension "ascii.pbm". The "ascii" part just helps me to distinguish these files from their binary versions, and is not required by any program.

• circle.ascii.pbm, a circle, drawn on a 200 by 200 grid;
• circle.png, a PNG version.
• feep.ascii.pbm, the example described above, on a 24 by 7 grid;
• feep.png, a PNG version.
• gerrymander.ascii.pbm, an image of the "Gerry-mander", on a 303 by 325 grid;
• gerrymander.png, a PNG version.
• letter_a.ascii.pbm, a capital A, using a 25 by 25 grid.
• letter_a.png, a PNG version.
• scs.ascii.pbm, the letters "SCS", on a 136 by 82 grid;
• scs.png, a PNG version.

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