20 Apr
1998
20 Apr
'98
5:49 a.m.
I'd love to write a program to "OCR" punched card images. Now, if
I only had some spare time. :-)
Scanners are cheap and ubiquitous. You could lay several cards on the
scanner at once, perhaps placing a specially-colored paper on the
normally white reflective lid, and presto - like chroma-key on video,
you can easily "see" the borders, index notch and holes. I wonder if
any of today's "paper port" auto-feeding cheapo scanners would handle
a punched card - I don't see why not.
It could save the card data in Jone's proposed file format. One advantage
of this system would be that it could handle aged cards that some physical
imperfection (like dents from rubber bands, folds, worn edges, etc.) that
might jam a card reader.
- John
Jefferson Computer Museum <http://www.threedee.com/jcm>
20 Apr
20 Apr
11:46 a.m.
I'd love to write a program to "OCR" punched card images. Now, if
I only had some spare time. :-)
Ain't that the truth.
Scanners are cheap and ubiquitous. You could lay
several cards on the
scanner at once, perhaps placing a specially-colored paper on the
normally white reflective lid, and presto - like chroma-key on video,
you can easily "see" the borders, index notch and holes. I wonder if
any of today's "paper port" auto-feeding cheapo scanners would handle
a punched card - I don't see why not.
I've got a Brother el-cheapo parallel port scanner that was able to
scan punch cards after I put the card (singular) in the torn paper
sleeve, in front of a piece of purple construction paper (I was going
for contrast and it was the darkest I had). The scans at 400 dpi look
great. I shrunk them 4:1 in Photoshop and saved them as GIFs. My
thought was to use the GIF library by Tom Boutell to slurp in a GIF,
run a high-frequency (edge detect) on them, guess the dpi based on
height and width, look for the notched corner (or be told the orientation
by the user) and pixel-column by pixel column, look for holes or the
absence thereof.
It could save the card data in Jone's proposed
file format. One advantage
of this system would be that it could handle aged cards that some physical
imperfection (like dents from rubber bands, folds, worn edges, etc.) that
might jam a card reader.
I hadn't thought of the benefits to damaged cards, but I agree on using
Doug Jones' format (which I just discovered, thanks to this thread).
The one drawback I've seen is speed. It's a pain in the butt to
stick a card in a scanner, scan the card, save the image, etc., etc. I
can't see reading much more than a couple of cards per minute. With
a modified scanner (to back up the scan area with black, not white), or
with suitably modified cards - say by xeroxing cards on a xerox machine
with a black background and scanning the xeroxes, it could be made to go
faster. Even a digital camera would probably be faster than a scanner.
With that speed, it's more efficient to take a block of lumber, dado
out a channel, drill 12 holes and wire up a dozen phototransistors into
a parallel port. Maybe a Basic Stamp could drive it? That way, any
machine, parallel equipped or not, could read the cards over a serial
port. The BS might even be trainable to output the file in D.J. format.
One issue I haven't gotten around is how rigidly oriented the cards have to
be. The technique I've been mulling around will work, providing that the
pixels of one card column don't overlap the pixels of another card column
in the same pixel column. I'm trying to do this in a portable manner,
in C, with code that is completely insensitive to OS and windowing scheme.
Right now, I'm scanning cards with Win95 (because of the PP scanner) and
will be interpreting them on a Linux box (because it's nicer to program).
Anyone who suggests VisualBasic will be forced to stuff the chad back into
a case of lace cards. ;-)
-ethan
4:42 p.m.
A non-text attachment was scrubbed...
Name: not available
Type: text
Size: 1066 bytes
Desc: not available
Url :
http://www.classiccmp.org/pipermail/cctalk/attachments/19980421/53ab104a/at…
6:15 p.m.
Punched cards have one major design bug IMHO
that's not shared by paper
tape. There's no 'column reference' on a card. On a tape, you can strobe
off the sprocket track, but alas on a card a totally unpunched column is
valid (=a space character).
True. If you write the program to keep careful time (and reject cards with
fewer than 80 chars), it _might_work. There is, of course, a brute-force
approach - 960 phototransistors. Additionally, one could build a 4 dpi
scanner (12 pixels and a stepper motor). With the steppper from a 5.25"
drive and either a mechanical amplifier (lever) to pull the 7" stroke or
either a) multiple 12-bit sensors or b) one 80-bit sensor w/3" stroke,
it wouldn't be that hard to make, not that I have the time to make a
contraption of that complexity.
My Documation M200 uses the leading edge of the card
as a reference. It
then counts pulses from a toothed wheel/pickup head on the card roller
shaft to deteremine where the columns should be.
So gut a mouse and stick a wheel in the wood block...
It's therefore almost impossible to make a
hand-pulled card reader.
Not with the reading accuracy of a mechanized reader, no.
If you can solve the timing problem, it's probably
easier/quicker to
program the microcontroller in assembly language. PIC assembler takes
about a day to learn...
I'm not worried about learning PIC assembler, it's a lack of a PIC
programmer and a portability issue... any boob that would have a deck
of cards to read should be able to put together a Stamp-based reader.
I wouldn't expect a straight-PIC reader to be as trivial for a non-
hardware hacker to assemble. Easier than hacking a PIC board would
be to build a C-64 based card reader... there's plenty of I/O bits if
you bogart the keyboard lines.
-ethan
21 Apr
21 Apr
12:06 p.m.
A non-text attachment was scrubbed...
Name: not available
Type: text
Size: 2550 bytes
Desc: not available
Url :
http://www.classiccmp.org/pipermail/cctalk/attachments/19980421/797b42fe/at…
20 Apr
20 Apr
6:17 p.m.
Regarding OCRing punch cards, I forgot to mention that I'm scanning the
back side to eliminate registation marks and other scribbles from
interfering with a rock-stupid program attempting to locate the holes.
-ethan
9595
days inactive
9596
days old
5 comments
3 participants
participants (3)
-
ard＠p850ug1.demon.co.uk -
erd＠infinet.com -
jfoust＠threedee.com