Processing tiff images for TessertactGUI

When processing images, tesseract is very restrictive about the images it processes.
It only touches TIFF files, with the extension "tif" and uncompressed.

Unfortunately, TesseractGUI is not very straightforward about the reason it rejects files from processing (it would just say "Error reading tesseract output").

Here's how you can identify the error and fix it:

Run tesseract from the command line to find out more about the rejection cause

cristi:~ diciu$ export TESSDATA_PREFIX=/Applications/TesseractGUI.app/Contents/Resources/
cristi:~ diciu$ /Applications/TesseractGUI.app/Contents/Resources/tesseract ~/Desktop/tiffs/page1.tif /tmp/ocrtest.txt
Tesseract Open Source OCR Engine
read_tif_image:Error:Illegal image format:Compression
/Applications/TesseractGUI.app/Contents/Resources/tesseract:Error:Read of file failed:/Users/diciu/Desktop/tiffs/page1.tif
Signal_exit 31 ABORT. LocCode: 3  AbortCode: 3

the problem with this particular TIFF file is the compression.

Fixing the problem

Step 1/ Download ImageMagick

Step 2/ Identify the TIFF file we want to use:

cd /Users/diciu/Downloads/ImageMagick-6.5.8/bin
export DYLD_FALLBACK_LIBRARY_PATH=/Users/diciu/Downloads/ImageMagick-6.5.8/lib
export MAGICK_HOME=/Users/diciu/Downloads/ImageMagick-6.5.8/
cristi:bin diciu$ tiffutil -info ~/Desktop/tiffs/page1.tif 
Directory at 0x837f8
  Subfile Type: (0 = 0x0)
  Image Width: 1200 Image Length: 2088
  Resolution: 200, 200
  Resolution Unit: pixels/inch
  Bits/Sample: 8
  Compression Scheme: Lempel-Ziv & Welch encoding
  Photometric Interpretation: palette color (RGB from colormap)
  Predictor: none
  Samples/Pixel: 1
  Rows/Strip: 10
  Number of Strips: 209
  Planar Configuration: Not planar
  Color Map: (present)

Note the compression scheme (LZW).

Step 3/ Uncompress the TIFF file

tiffutil -none ~/Desktop/tiffs/page1.tif -out ~/Desktop/tiffs/page1_uncompressed.tif

Now use page1_uncompressed.tif with tesseract.


Related:

• TesseractGUI


• tesseract