• Dave

    Dave - 2007-06-25

    I was wondering what the axes are on the pnghist.cgi and histogram.cgi plots.

    I was also wondering where in the code the histograms are generated, and where the values are stored (or if they are generated when needed).

    Thanks a bunch,

    • Andrey Filippov

      Andrey Filippov - 2007-06-25


      Histograms are generated in 2 stages (even 3). First is FPGA code (http://elphel.cvs.sourceforge.net/elphel/elphel353/elphel353/fpga/x3x3/histogram333.v?revision= that actually calculates histogram for each of the 4 Bayer components (including 2 greens), using 8-bit (after the gamma table) data.

      Two arrays are used in a ping-pong manner- while one is accumulating frame data the other is visible to the CPU, so it is not needed to synchronize readout with the frames.

      Next stage - driver, that reads the FPGA data to the array in system memory and exposes it (through mmap) to applications (like pnghist.cgi - http://elphel.cvs.sourceforge.net/elphel/elphel353/elphel353/apps/png/pnghist.c?view=markup and histogram.cgi)

      Now I'm converting drivers to be more php-friendly and there will be php access to histogram data too.


    • Dave

      Dave - 2007-06-26

      Thanks a lot for the quick response.


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