Re: [hpoj-devel] ptal-hp scan changes (T series now supported!)

[<pa...@rc...>]

Hi, Joe.

Joe Piolunek wrote:
> I'm happy to see color scanning begin to work.
...
> Some of the defaults work well. Using the command "ptal-hp mlc:par:0 scan 
> -length 1110" produced a 100x100 color scan that didn't quite match the size 
> of the original, but was close.
> 
> The scanned pages never seem to display or print at the original 
> size (either too small or too large). For pc-assisted copying, would 
> automatic scaling be needed?
If none of the device-native resolutions are quite right, then scaling might
need to be done.  However, if the hpinkjet driver is really capable of 300
dpi the way it claims, then it seems to me that you should be able to scan
and print at that resolution and not need any scaling.  What threshold of
resolutions did you observe between too small and too large?

> The color scans always seem somewhat grainy, even at -res 200. My system 
> doesn't handle color 300x300 scans well, so I haven't tried it again.
I've scanned on many different devices in my testing but haven't been paying
much attention to the image quality.  Here are some thoughts off the top of
my head:

- Depending on what you're scanning, especially at a higher resolution
you might end up seeing the dithering that was used when the page was
originally printed.

- It's possible that the scanning hardware on an older model like the 600
doesn't have quite as good clarity as a more recent model (but I don't know
for sure).  There might be some image processing that can be done in software
to improve this, but IMO this is best left to dedicated IP tools like GIMP.
Of course, a copy app might need to do something like this automatically.

- There is a "sharpening coefficient" PML object on some models which may
make a difference.  However, my sources indicate that it was first supported
on the PSC 300 series, which came out after the OfficeJet 600 series.  Try
"ptal-pml mlc:par:0 get 1.2.2.1.15" and see if you get an error back.  If
not, then try hacking a different value into "int sharpeningCoefficient=0x37;"
in ptal-hp, since I haven't yet made it adjustable on the command line.

- This probably isn't the right answer, but the scanner strip might be in
need of cleaning.  Just be careful not to damage anything if you try to clean
it.

> When trying to scan with "-res 200" , the printer often quits near the end of 
> the scan and displays the LCD message "SYSTEM ERROR2252". I think it also 
> happened once at -res 150. After power cycling the printer, it is able to 
> scan again, but only after resetting  its clock. I used ptal-hp to do that.
I've seen problems like this under certain circumstances.  I'll need to
research this to find out what's causing it.  From your description it sounds
like it's repeatable but doesn't happen every time.

> When opening out.jpg in gimp, an error message often appears that is similar 
> to  "Corrupt JPEG data: 8472 extraneous bytes before marker 0xd9". The number 
> of extraneous bytes varies, but the message always ends in '0xd9'.
That's because the length you specified was too short, and it truncated the
image.  However, it's probably OK if you're not missing anything important
at the end.

David