Re: QwtSpectrogram problems...

[Joey M. <jo...@sw...>]

On May 26, 2006, at 1:45 PM, Uwe Rathmann wrote:

>> This code make a somewhat nicer looking color bar, but I have no idea
>> how to incorporate into Qwt.
>
> This is what QwtColorMap is about. You can have any type of color  
> mapping by
> implementing YourColorMap::rgb and YourColorMap::colorIndex.
>
> If you can improve the implementation of QwtLinearColorMap or find  
> a new
> interesting type of color map, please contribute it to Qwt.

Still working on the logarithmic thing, but thought I would share a  
new color bar before I go home for a long weekend.  I need a color  
bar that goes from blue to red, so that what I started with.  Anyway,  
change the main.cpp in examples/spectrogram to add these lines:

QwtLinearColorMap colorMap(Qt::blue, Qt::red);

     const int numcolors = 1000;  // 1000 is the max?
     QColor myColor (Qt::blue);
     double delta = 1.0 / (double) numcolors;
     double deltaHue = myColor.hueF () / (double) numcolors;
     double whichColor = 0.0;
     double whichPos = 1.0;
     for (int i = 0; i < numcolors; i++)
     {
        myColor.setHsvF(whichColor, 1.0, 1.0);
        colorMap.addColorStop (whichPos, myColor);
        whichColor += deltaHue;
        whichPos -= delta;
     }

I think its much nicer!  Its like a bad acid trip!  :-)

If there is a better way to do this, let me know.

Joey