Fail to decode after printing: Error: cannot find upper left corner about optar

[monperrus]

For the record, finally got 0% error:

• with XCROSSES=45 and YCROSSES=65
• with TIF scan instead of JPG
• by decreasing scanning DPI to 400 (counter-intuitive)

[monperrus]

Encoding a different file (bigger so fewer blank spaces), plus using the repo's pgm2ps plus a new scan.

[colindean]

Note: I'm not the original author; I have this repo because the original source code wasn't in one and was hard to find.

It's been a while since I've tried a print/scan cycle. Most problems are a result of inadequately high-resolution printing or inadequately high-resolution scanning, and mostly the latter. Can you verify your printing and scanning resolutions meet the recommendation in the documentation?

[monperrus]

Thanks for your answer, everything is at 600 DPI but still have the problem.

[colindean]

Try scanning at 1200 DPI.

Are you able to share the original image that you used to create hard copy?

[monperrus]

Try scanning at 1200 DPI.

I only have a 600 DPI scanner

[monperrus]

Tried again, the corners can now be found.

Hitting 63544 bits bad from 3196368, bit error rate 1.98801%. 68.3353% black dirt, 25.9364% white dirt and 3640 (5.72831%) irreparable.

I'll try Change XCROSSES and YCROSSES in optar.h to lower values which yields bigger pixels and lower capacity per page, but higher reliability.

Thanks!

[colindean]

When you "tried again," what did you do differently? A new scan?

[monperrus]

With my 600 DPI scanner and

#define XCROSSES 52 /* Number of crosses horizontally */
#define YCROSSES 74 /* Number of crosses vertically */

The percentage of irreparable drops to 0.68%.