This command works for me for the 1st image file. I'm using ImageMagick version 6.7.9-0 2012-08-17 Q16
:
convert 1school.jpg \
-scale 1000% \
-blur 1x65535 -blur 1x65535 -blur 1x65535 \
-contrast \
-normalize \
-despeckle \
-despeckle \
-type grayscale \
-sharpen 1 \
-posterize 3 \
-negate 1school.tif \
&& \
tesseract 1school.tif OUT && cat OUT.txt
Tesseract Open Source OCR Engine v3.01 with Leptonica
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SCHOOL
ZONE
The 2nd image requires a different command:
convert 15071917.jpg \
-type grayscale \
-negate \
-gamma 1 \
-contrast -contrast -contrast -contrast -contrast -contrast -contrast -contrast -contrast -contrast \
-normalize -normalize -normalize -normalize -normalize -normalize -normalize -normalize -normalize -normalize \
-despeckle -despeckle -despeckle -despeckle -despeckle -despeckle -despeckle -despeckle -despeckle -despeckle \
15071917.tif \
&& \
tesseract 1school.tif OUT && cat OUT.txt
Tesseract Open Source OCR Engine v3.01 with Leptonica
Page 0
TE§§IO
Ok, the second one was not quite as successful. But you get the idea...
Here are the resulting images. Left are the originals, right results from commands: