JKD wrote: > Debugging the windows library that manages my scanner I see that the > first thing the driver does is create six tables with unknown purposes > at the moment. Theese tables are created in the following way. > > 1 - Loop with 3 iterations. I think one iteration per colour (not sure) > 2 - In each iteration, 2 tables are created. All tables have the same > size (0xff0 bytes = 4080.) and contains data of two bytes size (0x7f8 words = > 2040.) > 3 - The first table in each iteration is filled with zeroes. > 4 - The second table in each iteration is filled with 0x7f8 words with value > 0x4000 (16384.) > > It seems to be minimum values and maximum values for something but I'm > not sure of that. Could anyone have any idea about the purpose of theese > values? Gain values or something else ?. Gamma tables have only 255 > posible values and I've located them.
Indeed, I can imagine that those tables are used for offset / gain correction of individual CCD pixels. The values you describe could then be the default fill for a neutral offset/gain setting. In that case, the first table looks like the offset. The second table looks like the gain (in fixed point format, where 0x4000 represents a gain of 1, 0x2000 is a gain of 0.5, 0x8000 is a gain of 2, etc.) I think you're right that there is one set of gain/offset tables for each colour. Once thing that does not quite match is the size of the table: I would expect the number of table entries to be equal to the number of pixels in the CCD, but 2040 pixels is not even enough to reach 300 DPI. Bertrik
