Yet another Qwt curve fitting issue

[alexy]

Dear all,

please, don't beat me for posting such a topic once again. At the moment I'm trying to implement a typical functionality: to collect thousands of samples from hardware connected to PC and to precisely display it. I chose a Qwt library which is great and totally covers all of my "wishes". Every second a software receives about 1000 samples which are being saved to the HDD. After all samples are collected and sampling process is finished I need to discover what I've received. At this moment I enable the magnify/pan functionality of Qwt. And here is an "issue" that makes me mad a bit:

1. Magnifying to some interesting area of chart (step 1) is displayed at attached file with name wheel1.jpg

wheel1.jpg

2. On the next magnifying step (just one mouse wheel movement with default wheel factor 0.9) I see the following curve:

wheel2.jpg

3. Obviously, the shape and detalization of the curve becomes worsened. And that occurs when I tried to zoom in.

I tried both QwtCurveFitters: QwtWeedingCurveFitter and QwtSplineCurveFitter, but with no result at the moment. A magnifier is used with mostly default settings:

QwtPlotMagnifier*  magnifier = new QwtPlotMagnifier( ui->chart->canvas() );
    magnifier->setMouseButton( Qt::MidButton );
    magnifier->setWheelFactor( 0.9 ); // 0.95

QwtPlotMagnifier*  magnifier = new QwtPlotMagnifier( ui->chart->canvas() );
    magnifier->setMouseButton( Qt::MidButton );
    magnifier->setWheelFactor( 0.9 ); // 0.95

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Could you please help to make it behavior to be more predictable and logically clear.

[Uwe]

From your question it is not clear what you have implemented and what you want to achieve !

I'm pretty sure, that the magnifier works like expected, when not using any curve fitting. But then you are trying to improve the performance of your plot by introducing some curve fitting algo - and here is where you run into problems, right ?

Uwe