[sane-devel] escl backend not working with HP ScanJet Pro 4500 fn1[99F5CD] adf, platen scanner

[Karl Weber]

Hi,

you might remember that I am having trouble scanning from HP ScanJet Pro 4500 
fn1 with the hpaio backend when using ADF or Duplex as source, but not when 
scanning from the Flatbed.

Since this scanner supports AirPrint (according to the manual), I tried the 
escl backend as well, but it does not work at all, not even when scanning from 
the Flatbed. My understanding, however, is, that this should work. Am I right?

First, the scanner is recognized with both backends:

scanimage -L
device `escl:http://192.168.5.20:8080' is a HP ScanJet Pro 4500 fn1[99F5CD] 
adf,platen scanner
device `hpaio:/net/hp_scanjet_pro_4500_fn1?ip=192.168.5.20&queue=false' is a 
Hewlett-Packard hp_scanjet_pro_4500_fn1 all-in-one

When using escl it supports even more options then when using the hpaio 
backend, which already is an advantage for the ecsl backend. (As shown by --
help.)

When testing the scanner with the -T option I get the following error

scanimage -T -d 'escl:http://192.168.5.20:8080'
Output format is not set, using pnm as a default.
scanimage: rounded value of br-x from 215.9 to 215.9
scanimage: rounded value of br-y from 355.6 to 355.6
scanimage: sane_start: Invalid argument

When debugging with SANE_DEBUG_ESCL=150 SANE_DEBUG_DLL=100  scanimage -v -v -v 
-T -d 'escl:http://192.168.5.20:8080' 2>xxx.log

the log contains the following part

[11:24:25.215061] [escl] Create NewJob : /
[11:24:25.215284] [escl] escl_curl_url: URL: http://192.168.5.20:8080/eSCL/
ScanJobs//NextDocument
[11:24:25.215349] [escl] Before use hack 
[11:24:25.215378] [escl] After use hack 
[11:24:31.188234] [escl] eSCL scan : [Success]  real read (11868)
[11:24:31.194000] [escl] Error : 
poppler_document_new_from_data[11:24:31.194025] [escl] 2-Size Image (0)[0x0|
0x0]
scanimage: sane_start: Invalid argument
[11:24:31.194036] [dll] sane_cancel(handle=0x563d201082a0)
[11:24:31.194041] [escl] escl sane_cancel
[11:24:31.194133] [escl] escl_curl_url: URL: http://192.168.5.20:8080/eSCL/
ScanJobs//NextDocument

Could you give me some help here? I would prefer to use the escl backend over 
the hpaio backend, since the former offers more options than the  latter. 
However the former does not seem to work at all.

Thanks in advance!
Best regards
Karl