Theodore Kilgore wrote: > Matter of fact, I did do soem searching about "gamma" and I did come up > with an impression, at least: It seems to be a correction for > non-linearity of gain in the hardware (i.e. hardware does not respond in > linear fashion to a certain kind of stimulus, so we do something to fix > that).
Right, that's probably the most common description. Often an arbitrary table or function is used for gamma correction, sometimes a function like out = pow(in, x) is called "gamme correction" and x is called the "gamma value". Occasionally, one can find 1/x being called the gamma value. > The raw downloaded data for one 352x288 picture is exactly 352x128=101376 > bytes. If you put this directly into a file, you get a file of exactly > 101376 bytes. If you stick a ppm header on it you have a file with a ppm > header on it, and you get an error message if you try to view it. For a PPM file of 352x288 pxiels you'll need 352x288x3 bytes. (1 byte for red, one for green, one for blue) > If I am not mistaken, this is 8-bit color, since I recall somewhere seeing > that the camera gives 256 colors. Also this would fundamentally make sense > to me because the actual data gives exactly one pixel per byte. So I > guess a natural question might be, that how many "standard" ways are there > by which 8-bit color at one pixel can be represented by one byte? As far as i know, most if not all CCD sensors have a color filter in front of each sensor element, so that one element "sees" only red light, and another one only green or blue light. A camera with better firmware will build some interpolated values for the "missing colors" of a pixel, or the data from three sensor elements may be merged into one pixle value. I would that your camera simply delivers the raw data. > > > And as to this particular instance, I suspect the order RGB is the one > being used, not GRB or GBR or such. Peter already mentioned that the best way to get a clue about the color representation within the scan data is to make photos of pure red/green/blue areas. This should show data with repeate sequences of two bytes with smaller values and one byte with a larger value, if my guess is right. And if data for all colors is stored in one byte, you'll also quickly get a clue, which bits represents which colors. But I wold bet a few virtual beers that the camera delivers one color channel per byte. Abel
