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Thread: Is FilterPointsAggressive property using max-min decimation algorithm?

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    Question Is FilterPointsAggressive property using max-min decimation algorithm?

    so is this algorithm used when that property is checked?
    http://digital.ni.com/public.nsf/all...2576020075F784

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    Default Re: Is FilterPointsAggressive property using max-min decimation algorithm?

    The basic idea is the same, but as the page does not explain its algo ( only the effect ) and I can't tell you how similar it is to what Qwt does.

    In Qwt sequences of lines, that end up at the same x position are replaced by a maximum of 3 vertical lines, so that the outcome remains being a polygon ( the same is implemented for y coordinates and horizontal lines ).


    • entering point
    • minimum
    • maximum
    • leaving point


    So in the worst case you have 3 lines per pixel + 1 line connecting the pixels.

    In general it would also be possible to have even less lines by giving up having a polygon of connected lines. This would lead to even less work for the raster paint engine as the path "enter-min-max-leave" might have to pass some pixels twice.

    Uwe

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    Default Re: Is FilterPointsAggressive property using max-min decimation algorithm?

    Quote Originally Posted by Uwe View Post
    In general it would also be possible to have even less lines by giving up having a polygon of connected lines. T
    Am I understanding correctly, that you are saying that I can plot just dots, not lines? I.e. a dot plot, instead of the line plot?

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    Default Re: Is FilterPointsAggressive property using max-min decimation algorithm?

    Quote Originally Posted by r2com View Post
    Am I understanding correctly, that you are saying that I can plot just dots, not lines? I.e. a dot plot, instead of the line plot?
    Of course you can print dots as well - this is what QwtPlotCurve::Dots style does ( a scatter plot ). If you want to go this way have a look at the scatterplot example. It does a completely different type of optimization, one that works for unordered points, is independent of hardware acceleration ( no OpenGL required ) and can be processed multithreaded.

    But this is totally unrelated to my previous answers.

    Uwe

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    Default Re: Is FilterPointsAggressive property using max-min decimation algorithm?

    Quote Originally Posted by Uwe View Post
    In general it would also be possible to have even less lines by giving up having a polygon of connected lines.
    I am not quite understanding what you mean? How can I do it on my side? Or is it something what has to be coded inside SVN trunk cor Qwt itself?

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