166 lines
7 KiB
Text
166 lines
7 KiB
Text
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GOCR (JOCR at SF.net)
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GOCR is an optical character recognition program, released under the
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GNU General Public License. It reads images in many formats and outputs
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a text file. Possible image formats are pnm, pbm, pgm, ppm, some pcx and
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tga image files. Other formats like pnm.gz, pnm.bz2, png, jpg, tiff, gif,
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bmp will be automatically converted using the netpbm-progs, gzip and bzip2
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via unix pipe.
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A simple graphical frontend written in tcl/tk and some
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sample files are included.
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Gocr is also able to recognize and translate barcodes.
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You do not have to train the program or store large font bases.
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Simply call gocr from the command line and get your results.
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To see installation instructions, see the INSTALL file.
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How to start? (QUICK START)
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---------------------------
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Some examples of how you can use gocr:
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gocr -h # help
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gocr file.pbm # minimum options
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gocr -v 1 file.pbm >out.txt 2>out.log # generate text- and log file
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djpeg -pnm -gray text.jpg | gocr - # using JPEG-files
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gzip -cd text.pbm.gz | gocr - # using gzipped PBM-files
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giftopnm text.gif | gocr - # using GIF-files
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gocr -v 1 -v 32 -m 4 file.pbm # zoning and out30.bmp output
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xli -geometry 400x400 out30.bmp # see details using xli (recommanded viewer)
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wish gocr.tcl # X11-tcl/tk-frontend (development version)
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# see manual pages for more details
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How to get image files?
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-----------------------
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Scan text pages and save it as PGM/PBM/PNM file. Use a program such as
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The GIMP or Sane. You can also use netpbm-progs to convert several image
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formats into PGM/PBM/PNM. The tool djpeg can be used to convert jpeg into pgm.
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If you have a POSIX compatible system like linux and PNM-tools, gzip and bzip2
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are installed, you are lucky and gocr will do conversion
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from [.pnm.gz, .pnm.bz2, .jpg, .jpeg, .bmp, .tiff, .png, .ps, .eps]
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to [.pgm] for you. This list can easily be extended editing src/pnm.c.
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Gocr also comes with some examples, try: make examples.
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Memory limitations
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------------------
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WARNING!!!
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If you use a 300dpi scan of A4 letter, the image is about 2500x3500 pixels and
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gocr requires 8.75MB for storing the picture into the memory. Not only that,
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but gocr may create a 2nd copy, using a total of 17MB. This is independent
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of using b/w or gray-scale images. Be sure that you have enough RAM installed
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in your machine! Alternatively you can cut the picture into small pieces.
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You can use the pnmcut, from the netpbm package to cut the file. Example:
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pnmcut -left 0 -right 2500 -top 0 -height 1000 bigfile.pnm > smallfile.pnm
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And then use gocr in the cropped image as usual. Take care: if you chopp the
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characters, gocr won't be able to understand that line.
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Future versions will take care of this issue automatically.
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Limitations
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-----------
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gocr is still in its early stages. Your images should fit in these requirements
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if you want a good output:
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- good scans (all chars well seperated, one column, no tables etc, 12pt 300dpi)
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should work well
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- fonts 20-60 pixels ( 5pt * 1in/72pt * 300 dpi = 20 dots )
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- output of image file for controlling detection
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And note that speed is very slow (this will be changed when recognition works
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well)
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12pt 300dpi 1700x950 16lines 700chars 22x28 P90=40s..90s v0.2.3 (gcc -O0)
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You can try to optimize the results:
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- make good scans/treat image
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- try to change the critical gray level (option -l <n>)
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- control the result on out10.png, out30.png (option -v 32)
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example: ./gocr -v 32 -m 4 -m 256 -m 56 ~/aac.jpg # only check layout
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- enlarge option -d <n> for high resolution images which are noisy
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- try different combinations for option -m <n>
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- for thousends of documents with same font
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you can use/create a database (-m 2/-m 130)
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- use options -d 0 -m 8 on screen shots (font8x12)
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- use filter option -C to through out wrong recognized chars (ex: gothic)
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What does >> NOT << work at the moment:
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- complex layouts (try option -m 4)
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- bad scans, noisy/snowy images, FAX-quality images
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- serif fonts, italic fonts, slanted fonts
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- handwritten texts (this is valid for the next ten years I guess)
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the exisctence of autotrace can shorten this
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- rotated images (but slightly rotated images should be no problem)
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- small fonts (fax like) or mix of different font size
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- colored images (use gray or black/white)
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- Chinese, Arabian, Egyptian, Cyrillic or Klingon fonts
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How it works or how it should work?
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- put the entire file into RAM (300dpi grayscale recommended)
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- remove dust and snow
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- detect small angle (lines which are not horizontal)
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- detect text boxes (option -m 4)
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- detect text-lines
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- detect characters
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- first step recognition (every character has its own empirical procedure)
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- no neural network or similar general algorithms
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- analyze not detected chars by comparison with detected ones
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- try to divide overlapping chars
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- testwise: compare all letters (like compression of pictures)
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- for more details look to the gocr.html documentation
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Why the result of the new version are worse compared to the old version?
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- the algorithms of gocr are sometimes evolutionary, a fine tuned old
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algorithm will be replased by a completly new algorithm which is more
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general but a bit worse for your problem.
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Please send your sample and give the new algo the chance to become
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better as the old one.
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Security
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--------
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Because gocr only reads and writes files it is quite sure, except the
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popen-function which allows you to call gocr with non-pnm-image formats
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directly. The popen function can be misused to start other probably
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dangerous programs.
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If you care about conversion to pnm format, you can safely disable
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popen-function by removing "#define HAVE_POPEN 1" from config.h before
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compiling the gocr package.
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How can you help gocr?
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----------------------
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- Send comments, ideas and patches (diff -ru gocr_original/ gocr_changed/).
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- If you have a lot of money, spend a bit (paypal). Ok, paypal has changed,
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so please forget about it. Also the importand problem is now the missing
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spare time for coding.
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- I always need example files (.pbm.gz or jpeg <100kB) for testing
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the behavior of the ocr engine under different conditions,
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because scanning does take a lot of time which I do not have.
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But do not send files which are not convertable by commercial ocr programs
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or which are protected from copying and electronic processing by copyright.
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That will help, to get the world's best OCR open source program. :) Thanks!
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- Please dont send captchas.
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- Send me your results (errors,num_chars,dpi) and if possible results
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and name of professional OCR programs for statistics.
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- Read OCR literature, extract the essentials and send a short report
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to me ;).
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- If you have a good idea, how to manage some OCR-tasks, tell me!
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- Tell your friends about gocr. Tell me about your success. Be happy.
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After all, is it gocr or jocr?
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------------------------------
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The original name of this project is gocr, from GNU Optical Character
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Recognition. Another project is using the same name, however; so the
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name was changed to jocr. If you have a good idea for a name, please
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send it.
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Latest news
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------------
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http://jocr.sourceforge.net
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Authors: (see AUTHORS)
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