1.\" 2.Dd September 27, 1991 3.Dt PBM 5 4.Os 5.Sh NAME 6.Nm pbm 7.Nd portable bitmap file format 8.Sh DESCRIPTION 9The portable bitmap format is a lowest common denominator monochrome 10file format. 11It was originally designed to make it reasonable to mail bitmaps 12between different types of machines using the typical stupid network 13mailers we have today. 14Now it serves as the common language of a large family of bitmap 15conversion filters. 16The definition is as follows: 17.Pp 18.Bl -bullet -compact 19.It 20A "magic number" for identifying the file type. 21A pbm file's magic number is the two characters "P1". 22.It 23Whitespace (blanks, TABs, CRs, LFs). 24.It 25A width, formatted as ASCII characters in decimal. 26.It 27Whitespace. 28.It 29A height, again in ASCII decimal. 30.It 31Whitespace. 32.It 33Width * height bits, each either '1' or '0', starting at the top-left 34corner of the bitmap, proceeding in normal English reading order. 35.It 36The character '1' means black, '0' means white. 37.It 38Whitespace in the bits section is ignored. 39.It 40Characters from a "#" to the next end-of-line are ignored (comments). 41.It 42No line should be longer than 70 characters. 43.El 44.Pp 45Here is an example of a small bitmap in this format: 46.Bd -literal 47P1 48# feep.pbm 4924 7 500 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 510 1 1 1 1 0 0 1 1 1 1 0 0 1 1 1 1 0 0 1 1 1 1 0 520 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 1 0 530 1 1 1 0 0 0 1 1 1 0 0 0 1 1 1 0 0 0 1 1 1 1 0 540 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 550 1 0 0 0 0 0 1 1 1 1 0 0 1 1 1 1 0 0 1 0 0 0 0 560 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 57.Ed 58.Pp 59Programs that read this format should be as lenient as possible, 60accepting anything that looks remotely like a bitmap. 61.Pp 62There is also a variant on the format, available 63by setting the RAWBITS option at compile time. 64This variant is 65different in the following ways: 66.Pp 67.Bl -bullet -compact 68.It 69The "magic number" is "P4" instead of "P1". 70.It 71The bits are stored eight per byte, high bit first low bit last. 72.It 73No whitespace is allowed in the bits section, and only a single character 74of whitespace (typically a newline) is allowed after the height. 75.It 76The files are eight times smaller and many times faster to read and write. 77.El 78.Sh AUTHORS 79Copyright (C) 1989, 1991 by 80.An Jef Poskanzer . 81.\" Permission to use, copy, modify, and distribute this software and its 82.\" documentation for any purpose and without fee is hereby granted, provided 83.\" that the above copyright notice appear in all copies and that both that 84.\" copyright notice and this permission notice appear in supporting 85.\" documentation. This software is provided "as is" without express or 86.\" implied warranty. 87