I may have answered one of my questions after researching the sane pages. The "curve tool" is a transfer function graph. http://www.scantips.com/curve2.html Good stuff. R/ Michael -----Original Message----- From: Michael Watson [mailto:[email protected]] Sent: Friday, January 04, 2013 5:28 PM To: 'sane-devel at lists.alioth.debian.org' Subject: Sane Scanimages Too Dark
Request insights from the brain trust. Sane scanimage files are too dark while windows' scans (Canon drivers/applications) are fine? I have an archlinuxarm box and an Lide210 scanner. Utilizing SaneTwain on a windows box the network scans were too dark. Similarly, scanimage (local) scans were also too dark. Trying to compensate the SaneTwain gamma was experimented with. What worked well was a straight line curve that maxed out at the top while 3/4 of the way to the right (0,0 --> 191,65535 --> 65535, 65535) and not the top right corner ((0,0 --> 65535, 65535). With this information the scanimage (local) was adjusted with gamma4scanimage 1.75 0 181 255 65535, which works well. I do not understand why the upper limit is at approximately 191 and not 255. >From the sane debug it appears the gamma is initially set to 1.7, which produces dark images because the initial gamma table is equivalent to gamma4scanimage 1.7 0 255 255 65535? [genesys] sanei_genesys_create_gamma_table: size = 256, maximum = 65535, gamma_max = 65535, gamma = 1.7 Also, SaneTwain will send the gamma table to the scanner when initially set. If it is saved (ini file) and SaneTwain is started up, the custom gamma table checkbox (custom-gamma=yes/no) has no visible impact on the scanned image - too dark. Any insights appreciated. R/ Michael -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.alioth.debian.org/pipermail/sane-devel/attachments/20130104/6d0287f5/attachment.html>
