Extracting data from oscilloscope bitmap screen capture

[CdeMills]

Dear Octavians,

this is a follow-up of my previous post; I tested most of the suggested
graph-to-data software mentioned.

All are based on the same assumption: the image is produced by a curve
tracer, that is, some device where x or absolute displacement speed is
constant, resulting in lines with uniform vertical width.

I enclose a small excerpt of the image produced by the oscilloscope.
- each vertical graduation is produced from 25 values, the vertical
amplitude representing the max and the min of those 25 points; the vertical
resolution is quite limited
- the color seems to be linked to the points density:
  when the vertical bar is bright, the average value is greater than the bar
mid-point
  when the vertical bar is faded, the average value is smaller than the bar
mid-point

Basically the vertical point density is non-uniform and somehow translated
by the brightness level. The data extraction software that I tested produced
different coverages between bright and faded zones, but with inverted logic,
taking a lot of points on isolated spikes and less on bright zones; so the
statistics are completely modified.

So I come back with the original question: how can I digitze the graph to
extract data; taking into account the color as a density indicator ?

Regards

Pascal 











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