PGMA Files
Portable Gray Map (ASCII)

PGMA is the ASCII portable gray map format. It is a simple grayscale image 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. An ASCII PGM file's magic number is the two characters "P2".
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, again in ASCII decimal.
Whitespace.
Width * height gray values, each in ASCII decimal, 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.

Characters from a "#" to the next end-of-line are ignored (comments). No line should be longer than 70 characters.

Example PGMA file:

        P2
        # feep.pgma
        24 7
        15
        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 3  3  3  3  0  0  7  7 7  7  0  0 11 11 11 11 0  0 15 15 15 15  0
        0 3  0  0  0  0  0  7  0 0  0  0  0 11  0  0  0 0  0 15  0  0 15  0
        0 3  3  3  0  0  0  7  7 7  0  0  0 11 11 11  0 0  0 15 15 15 15  0
        0 3  0  0  0  0  0  7  0 0  0  0  0 11  0  0  0 0  0 15  0  0  0  0
        0 3  0  0  0  0  0  7  7 7  7  0  0 11 11 11 11 0  0 15  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

PGMA File Characteristics:

ASCII
Gray
2D
No compression
1 image

Related Data and Programs:

PBMA is a data directory which describes ASCII Portable Bit Map files.

PGMB is a data directory which describes binary Portable Gray Map files.

PPMA is a data directory which describes ASCII Portable Pixel Map files.

Reference:

the NETPBM homepage.

Programs to create a PGMA file:

The gnuplot command "set terminal pbm gray" will cause the graphics information to be written to a PGM file.

Programs and routines to read a PGMA file:

MATLAB can read a PGMA file with a command like A=imread('file','PGM').
pgma_io a set of C++ routines;
pgma_io a set of FORTRAN90 routines;
pgma_io, a set of MATLAB functions.
The Visual Toolkit routine vtkPNMReader can read an ASCII PGM file into VTK.

Programs and routines to write a PGMA file:

MATLAB can write a PGMA file with a command like imwrite(a,'filename','PGM').
pgma_io a set of C++ routines;
pgma_io a set of FORTRAN90 routines;
pgma_io, a set of MATLAB functions.
The Visual Toolkit routine vtkPNMWriter can write a VTK image to an ASCII PGM file.

Programs to view a PGMA file include:

AVS includes a module read_any_image which can view a PGMA file;
GIMP, the GNU Image Manipulation Program, can view a PGMA file.
gqview, a Linux image viewing program, can view a PGMA file.
imgview, an image viewing program from ImageVision can view a PGMA file.

MATLAB can display a PGMA file, once it is read in, with a command like


            A = imread ( 'file.pgm', 'PGM' )
            image ( A )

xv can view a PGMA file on a unix system by a command like
```
            xv file.pgm
          
```

Programs to convert a PGMA file to another format:

cjpeg can convert a PGM file to JPEG format.
convert, a program that is part of ImageMagick, can convert a PGMA 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 PGMA file and write out a copy in a variety of formats.
PGMA_TO_PGMB is a C++ program which can convert a PGMA file to PGMB format.
The NETPBM program PGMTOFITS converts a PGMA file to FITS format.
xv can read a PGMA file and write out a copy in BMP, FIT, GIF, JPG, PBM, PPM, RGB or TIF format.

Programs to convert a file to PGMA 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 PGMA format. However, to force the ASCII format, you must include the switch "-compress none".
djpeg converts a JPEG file to PGMA format.
GIMP, the GNU Image Manipulation Program, can read a file in a variety of formats, and write it out as a PGMA file.
The NETPBM program FITSTOPGM converts a FITS file to PGMA format.
PGMB_TO_PGMA is a C++ program which can convert a PGMB file to PGMA format.
xv can read a file in a BMP, FIT, GIF, JPG, PBM, PPM, RGB or TIF format, and write it out as a PGMA file.

Sample PGMA files:

baboon.pgma, a 512 by 512 image of a baboon.
balloons.pgma, a 640x480 image of a couple, with balloons.
barbara.pgma,a 512x512 image
columns.pgma, a 640x480 image of a person standing by some columns;
feep.pgma, a simple 7 by 24 example that displays "FEEP" in block letters.
lena.pgma a 512x512 image.
pbmlib.pgma, a 600x200 image created by PBMLIB.
tracks.pgma, a 300x200 image that looks like tracks.

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Last revised on 05 September 2006.

PGMA Files Portable Gray Map (ASCII)