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GOCR(1) User's Manual GOCR(1)


gocr - command line text recognition tool


gocr [OPTION] [-i] pnm-file


gocr is an optical character recognition program that can be used from the command line. It takes input in PNM, PGM, PBM, PPM, or PCX format, and writes recognized text to stdout. If the pnm file is a single dash, PNM data is read from stdin. If gzip, bzip2 and netpbm are installed and your system supports popen(3) also pnm.gz, pnm.bz2, png, jpg, jpeg, tiff, gif, bmp, ps (only single pages) and eps are supported as input files (not as input stream), where pnm can be replaced by one of ppm, pgm and pbm.


show usage information
show version information
read input from file (or stdin if file is a single dash)
send output to file instead of stdout
send errors to file instead of stderr or to stdout if file is a dash
progress output to file (file can be a file name, a fifo name or a file descriptor 1...255), this is useful for GUI developpers to show the OCR progress, the file descriptor argument is only available, if compiled with __USE_POSIX defined
database path, a final slash must be included, default is ./db/, this path will be populated with images of learned characters
output format of the recognized text (ISO8859_1 TeX HTML XML UTF8 ASCII), XML will also output position and probability data
set grey level to level (0<160<=255, default: 0 for autodetect), darker pixels belong to characters, brighter pixels are interpreted as background of the input image
set dust size in pixels (clusters smaller than this are removed), 0 means no clusters are removed, the default is -1 for auto detection
set spacewidth between words in units of dots (default: 0 for autodetect), wider widths are interpreted as word spaces, smaller as character spaces
be verbose to stderr; verbosity is a bitfield
only verbose output of characters from string to stderr, more output is generated for all characters within the string, the underscore stands for unknown chars, this function is usefull to limit debug information to the necessary one
only recognise characters from string, this is a filter function in cases where the interest is only to a part of the character alphabet, you can use 0-9 or a-z to specify ranges, use -- to detect the minus sign
set value for certainty of recognition (0..100; default: 95), characters with a higher certainty are accepted, characters with a lower certainty are treated as unknown (not recognized); set higher values, if you want to have only more certain recognized characters
output this string for every unrecognized character (default is "_")
set oprational mode; mode is a bitfield (default: 0)
if bool is non-zero, only recognise numbers (this is now obsolete, use -C "0123456789")

The verbosity is specified as a bitfield:

print more info
list shapes of boxes (see -c) to stderr
list pattern of boxes (see -c) to stderr
print pattern after recognition for debugging
print debug information about recognition of lines to stderr
create outXX.png with boxes and lines marked on each general OCR-step

The operation modes are:

use database to recognize characters which are not recognized by other algorithms, (early development)
switching on layout analysis or zoning (development)
don't compare unrecognized characters to recognized one
don't try to divide overlapping characters to two or three single characters
don't do context correction
character packing, before recognition starts, similar characters are searched and only one of this characters will be send to the recognition engine (development)
extend database, prompts user for unidentified characters and extends the database with users answer (128+2, early development)
switch off the recognition engine (makes sense together with -m 2)


Joerg Schulenburg (see for EMAIL)
First version of man page by Tim Waugh <>


This man page documents gocr, version 0.52.


Report bugs to Joerg Schulenburg


More details can be found at /usr/share/doc/gocr-X.XX/gocr.html. Also read /usr/share/doc/gocr-X.XX/README to learn, how to improve results.


output verbose information, out30.png is created to see details of recognition process
verbose output for unknown chars and chars Y and V
convert a jpeg file to pnm format and input via pipe
20 Sep 2018 Linux