[sane-devel] Bug in snapscan or sane network protocolo?

Giuseppe Sacco giuseppe@eppesuigoccas.homedns.org
Thu, 09 Jun 2005 16:47:05 +0200

Hi all,
I am using an EPSON Perfection 1670 over the network, via saned, and I
just found a problem.

Basically I do a scan of 210.0x297.0mm, using a 200dpi resolution.
Prior to scan I call get_parameters and receive an *estimated* values
for lines, pixelsperline, bytesperline; after receiving this data I
receive the frame data.

The problem is that get_parameters says:

[snapscan] sane_snapscan_get_parameters (0x8090aa8, 0xbffffc24)
[snapscan] sane_snapscan_get_parameters: Using estimated data
[snapscan] sane_snapscan_get_parameters: depth = 8
[snapscan] sane_snapscan_get_parameters: lines = 2338
[snapscan] sane_snapscan_get_parameters: pixels per line = 1653
[snapscan] sane_snapscan_get_parameters: bytes per line = 4959

while, when scanning, I get a different amount of data:

[snapscan] inquiry: exposure time: 4.6 ms
[snapscan] inquiry: ms per line: 4.600000
[snapscan] inquiry: G2R_DIFF: 131
[snapscan] inquiry: B2R_DIFF: 134
[snapscan] inquiry: Chroma offsets=6; Red=6, Green:=3, Blue=0
[snapscan] inquiry: hardware config = 0xbd
[snapscan] inquiry: bits per pixel = 14
[snapscan] inquiry: pixels per scan line = 1652
[snapscan] inquiry: bytes per scan line = 4956
[snapscan] inquiry: number of scan lines = 2338
[snapscan] inquiry: effective buffer size = 64428 bytes, 27 lines
[snapscan] inquiry: expected total scan data: 11616864 bytes
[snapscan] sane_snapscan_start: after measuring speed:
        4956 bytes per scan line
        4.600000 milliseconds per scan line.
        ==>1077.391327 bytes per millisecond
[snapscan] scan

As you may notice, the "pixel per line" value changed. So when I try to
create the image I have less data than expected.

I see two possible options:

1. Change the snapscan algorithm to have better supposed values
2. Change the sane network protocol in order to get all corrected
   parameter *with* or *after* the scanned data.

Any comment?