43.25 The Portable Bitmap Package

There are dozens of formats used for graphics files across the computer industry. There are tiff files, PICT files, and gif files. There are different formats for displaying on different hardware, different formats for printing on different printers, and then there are the internal formats used by graphics programs. This means that importing a graphics file from one platform to another (or from one program to another) can be a large undertaking, requiring a filter written specially to convert from one format to the next.

netpbm	The netpbm package can be used to convert between a wide variety of graphics formats. netpbm evolved from the original Portable Bitmap Package, pbmplus , which was written by Jef Poskanzer. A group of pbmplus users on the Internet cooperated to upgrade pbmplus ; the result was netpbm .

The idea behind pbm is to use a set of very basic graphics formats that (almost) all formats can be converted into and then converted back from. This is much simpler than having converters to and from each individual format. These formats are known as pbm , pgm , and ppm : the portable bitmap, graymap, and pixmap formats. (A bitmap is a two-dimensional representation of an image; a graymap has additional information encoded that gives grayscale information for each bit; a pixmap encodes color information for each bit.) The name "pnm " is a generic name for all three portable interchange formats (with the n standing for "an y"), and programs that work with all three are said to be "anymap" programs.

The netpbm package contains well over a hundred conversion programs. There are three basic kind of programs:

• Programs that convert a graphics file to one of the pnm formats. For example, if I had a tiff file and I wanted to convert it to PostScript, I might start the process by using tifftopnm :

  % tifftopnm Hobbes.tiff > Hobbes.pnm
  
  

• Programs that convert from one of the pnm formats to another format. For example, if I wanted to convert the Hobbes.pnm file directly to PostScript, I could use pnmtops :

  % pnmtops Hobbes.pnm > Hobbes.ps
  
  

• Programs used to manipulate the image in pnm format. For example, if I wanted to crop the image, I could use pnmcut before I converted the file to PostScript and printed it:

  % tifftopnm Hobbes.tiff > Hobbes.pnm
  
  
  % pnmcut 10 10 200 200 Hobbes.pnm > Hobbes.cut
  
  
  % pnmtops Hobbes.cut > Hobbes.ps
  
  
  % lpr Hobbes.ps
  
  

  or, on one command line (and without cluttering your disk with intermediary files):

  % tifftopnm Hobbes.tiff | pnmcut 10 10 200 200 | pnmtops | lpr
  
  

I frequently like to create X11 (1.31 ) bitmaps out of pictures in newspapers or magazines. The way I do this is to first scan the picture in on a Macintosh and save it as tiff or PICT format. Then I ftp (1.33 ) the file to our UNIX system and convert it to pnm format, and then use pbmtoxbm to convert it to X bitmap format. If the picture is too big, I use pnmscale on the intermediary pnm file. If the picture isn't right-side-up, I can use pnmrotate and sometimes pnmflip before converting the pnm file to X11 bitmap format.

The programs provided with the netpbm package are far too many to discuss in detail, and some of these formats are ones that you've probably never even heard of. But here's a summary of them. Table 43.2 lists the conversion programs. Table 43.3 lists the programs that perform various kinds of editing, enhancement, or transformations on image files.

Table 43.2: Image Format Conversion Programs

Format	To pnm	From pnm
ASCII graphics	asciitopgm	pbmtoascii
AT&T 4425 terminal (132 col mode)		pbmto4425
Abekas YUV bytes	yuvtoppm	ppmtoyuv
Abekas YUV triplets (MPEG/JPEG)	yuvsplittoppm	ppmtoyuvsplit
Andrew Toolkit raster object	atktopbm	pbmtoatk
Atari Degas .pi1	pi1toppm	ppmtopi1
Atari Degas .pi3	pi3topbm	pbmtopi3
Atari compressed Spectrum file	spctoppm
Atari uncompressed Spectrum file	sputoppm
AutoCAD database or slide	sldtoppm	ppmtoacad
BBN BitGraph graphics		pbmtobbnbg
Bennet Yee "face" file	ybmtopbm	pbmtoybm
Biorad confocal microscope files	bioradtopgm
CMU window manager bitmap	cmuwmtopbm	pbmtocmuwm
DEC LN03+		pbmtoln03
DEC sixel format		ppmtosixel
DDIF format		pnmtoddif
Encapsulated PostScript preview bitmap		pbmtoepsi
Epson printer graphics		pbmtoepson
FITS	fitstopnm	pnmtofits
GEM .img file	gemtopbm	pbmtogem
GIF	giftopnm	ppmtogif
Gemini 10X printer graphics		pbmto10x
Gould scanner file	gouldtoppm
GraphOn graphics (compressed)		pbmtogo
Group 3 fax file	g3topbm	pbmtog3
HIPS	hipstopgm
HP LaserJet format		pbmtolj
HP PaintJet	pjtoppm	ppmtopj
HP PaintJet XL PCL file		ppmtopjxl
IFF ILBM	ilbmtoppm	ppmtoilbm
Img-whatnot	imgtoppm
Lisp Machine bitmap	lispmtopgm	pgmtolispm
MGR bitmap	mgrtopbm	pbmtomgr
MacPaint	macptopbm	pbmtomacp
Macintosh PICT	picttoppm	ppmtopict
Mitsubishi S340-10 printer format		ppmtomitsu
Motif UIL icon file		ppmtouil
NCSA ICR format		ppmtoicr
PCX	pcxtoppm	ppmtopcx
packed (PK) format font	pktopbm	pbmtopk
Photo-CD file	hpcdtoppm
PostScript "image" data	psidtopgm
PostScript (pstopnm uses ghostscript )	pstopnm	pnmtops
Fast PostScript creator		pbmtolps
Printronix printer graphics		pbmtoptx
SGI image file	sgitopnm	pnmtosgi
Solitaire image recorder format	sirtopnm	pnmtosir
SPOT satellite images	spottopgm
Sun icon	icontopbm	pbmtoicon
Sun rasterfile	rasttopnm	pnmtorast
TIFF file	tifftopnm	pnmtotiff
TrueVision Targa file	tgatoppm	ppmtotga
Unix plot(5) file		pbmtoplot
Usenix FaceSaver(tm)	fstopgm	pgmtofs
Windows (PC) bitmap	bmptoppm	ppmtobmp
X10 bitmap	xbmtopbm	pbmtox10bm
X10 window dump	xwdtopnm
X11 "puzzle" file		ppmtopuzz
X11 bitmap	xbmtopbm	pbmtoxbm
X11 pixmap	xpmtoppm	ppmtoxpm
X11 window dump	xwdtopnm	pnmtoxwd
Xim file	ximtoppm
XV "thumbnail" picture	xvminitoppm
Zeiss confocal microscopes	zeisstopnm
Zinc bitmap		pbmtozinc
doodle brush	brushtopbm
output from the MTV or PRT ray tracers	mtvtoppm
output from the QRT ray tracer	qrttoppm
portable bitmap		pgmtopbm
portable graymap		pbmtopgm
		ppmtopgm
portable pixmap		pgmtoppm
raw RGB bytes	rawtoppm
raw grayscale bytes	rawtopgm
text	pbmtext
three portable graymaps	rgb3toppm	ppmtorgb3
unknown	anytopnm

Table 43.3: Manipulating pnm Files

Program	Purpose
pbmlife	Apply Conway's rules of Life to a portable bitmap.
pbmmake	Create a blank bitmap of a specified size.
pbmmask	Create a mask bitmap from a regular bitmap.
pbmpscale	Enlarge pbm image with edge smoothing.
pbmreduce	Read a portable bitmap and reduce it N times.
pbmupc	Create a Universal Product Code bitmap.
pgmbentley	Bentleyize a portable graymap.
pgmcrater	Create cratered terrain by fractal forgery.
pgmedge	Edge-detect a portable graymap.
pgmenhance	Edge-enhance a portable graymap.
pgmhist	Print a histogram of the values in a portable graymap.
pgmkernel	Generate a convolution kernel (for pnmconvol use).
pgmnoise	Create a PGM made up of white noise.
pgmnorm	Normalize the contrast in a portable graymap.
pgmoil	Turn a portable graymap into an oil painting.
pgmramp	Generate a grayscale ramp.
pgmtexture	Calculate textural features on a portable graymap.
pnmalias	Antialias a PNM (remove jaggies).
pnmarith	Perform arithmetic on two portable anymaps.
pnmcat	Concatenate portable anymaps.
pnmcomp	Create composite image from two PNMs.
pnmconvol	General MxN convolution on a portable anymap.
pnmcrop	Crop a portable anymap.
pnmcut	Cut a rectangle out of a portable anymap.
pnmdepth	Change the maxval in a portable anymap.
pnmenlarge	Read a portable anymap and enlarge it N times.
pnmfile	Describe a portable anymap.
pnmflip	Perform one or more flip operations on a portable anymap.
pnmgamma	Perform gamma correction on a portable anymap.
pnmhisteq	Histogram equalize a PNM.
pnmhistmap	Draw a histogram for a PGM or PPM file.
pnmindex	Build a visual index of a bunch of anymaps.
pnminvert	Invert a portable anymap.
pnmmargin	Add a border to a portable anymap.
pnmnlfilt	Miscellaneous non-linear filters.
pnmnoraw	Force a portable anymap into plain format.
pnmpad	Add borders to a PNM.
pnmpaste	Paste a rectangle into a portable anymap.
pnmrotate	Rotate a portable anymap by some angle.
pnmscale	Scale a portable anymap.
pnmshear	Shear a portable anymap by some angle.
pnmsmooth	Smooth out an image.
pnmtile	Replicate a portable anymap into a specified size.
ppm3d	Merge two PPM files into a red/blue (3-D glasses) PPM.
ppmbrighten	Change image saturation and value on an HSV map.
ppmchange	Change one color into another color.
ppmdim	Dim a portable pixmap (similar to ppmbrighten).
ppmdist	Simplistic grayscale convert for color images.
ppmdither	Ordered dither for color images.
ppmflash	Brighten a picture (similar to ppmbrighten).
ppmforge	Fractal forgeries of clouds, planets, and starry skies.
ppmhist	Print a histogram of a portable pixmap.
ppmmake	Create a pixmap of a specified size and color.
ppmtomap	Extract all colors from a PPM file.
ppmmix	Blend together two portable pixmaps (fade between).
ppmnorm	Normalize the contrast in a portable pixmap.
ppmntsc	Make PPM look like a television image (dim every other row).
ppmpat	Make a pretty pixmap.
ppmquant	Quantize the colors in a portable pixmap down to a specified number.
ppmquantall	Run ppmquant on a bunch of files all at once, so they share a common colormap.
ppmqvga	Eight plane quantization.
ppmrelief	Run a Laplacian relief filter on a portable pixmap.
ppmshift	Shift rows randomly left and right (water reflection).
ppmspread	Displace pixels by random amounts (unfocus image).

bitmaps	The netpbm package is also distributed with a set of public domain bitmaps. We've put these bitmaps on the CD-ROM as well.