Qwt Plot using an image as background reference

[Tinou[FR]]

Hi all,
I'm french so excuse me for my English.

I have some problem on qwt, I generate a lot of graphics (polar graphics particulary) and save them as image (8000 images) so it take many time.
I want to use an image (of the curve are already same on 8000 images) for the background.

Does anyone have an idea ?
I see about canvas but I don't arrived to use it.

An example in image :
Lidar.png------->00001Lidar.png
Thank you for attention
Kind regards,
Tinou

[Tinou[FR]]

Any idea ?

[Uwe]

I want to use an image (of the curve are already same on 8000 images) for the background.

Well you could always load an image - assuming you are talking about some raster graphic format - as spectrogram, but in your case I wouldn't even spend a second on trying it. Scaling the antialiased lines from your image from your screenshot will result in in something horrible.

If you can't vectorize your images you should try to find out how they were calculated. When there is some mathematics behind the 8000 plots - maybe it is not so much work to show them as a regular curve.

Uwe

[Tinou[FR]]

Hi,
Thank you for reply.
I foud a solution here my code :

QImage img;
img.load(imgPath+"/Lidar.png");
qDebug() << img.size();
QBrush qbrush(img);
qbrush.setTextureImage(img);
qDebug() << "Taille" << qbrush.textureImage().size();

polarPlot->setPlotBackground(qbrush);


Here the result :
Image use for Background --------> Background --------> Image
Lidar.png-------->Lidar2.png-------->00001Lidar.png
But the problem is the brush is resize and I don"t know why, have you an idea?
Regards,
Tinou

[Uwe]

As said before: the idea itself is not a good one and I don't want to spend time on assisting you in running in the wrong direction.

Uwe

[Tinou[FR]]

Ok then I will try to found an other way. Thanks

Is that possible to attach an Item one time for all 8000 time?


EDIT : Ok then I have wrong since the beginning !!
It's not the "attach" who take time but the renderer as an image, any idea how optimise this??

[Uwe]

Ah o.k. - maybe now I got what you want.

class YourCurve: public QwtPolarCurve
{
...
    virtual void draw( QPainter *painter,
        const QwtScaleMap &azimuthMap, const QwtScaleMap &radialMap,
        const QPointF &pole, double radius,
        const QRectF &canvasRect ) const
    {
        if ( ( canvasRect.size() != m_image.size() ) || other_conditions_to_invalidate_the_image() )
        {
            m_image = QImage( canvasRect.size(), QImage::Format_ARGB32_Premultiplied );
            m_image.fill( 0 );
 
            QPainter p( &m_image );
            p.translate( -canvasRect.topLeft() );
            QwtPloarCurve::draw( &p, azimuthMap, radialMap, pole, radius, canvasRect );
        }
 
        painter->drawImage( canvasRect.topLeft(), m_image );
    }
 
    QImage m_image;
};

class YourCurve: public QwtPolarCurve
{
...
    virtual void draw( QPainter *painter,
        const QwtScaleMap &azimuthMap, const QwtScaleMap &radialMap,
        const QPointF &pole, double radius,
        const QRectF &canvasRect ) const
    {
        if ( ( canvasRect.size() != m_image.size() ) || other_conditions_to_invalidate_the_image() )
        {
            m_image = QImage( canvasRect.size(), QImage::Format_ARGB32_Premultiplied );
            m_image.fill( 0 );

            QPainter p( &m_image );
            p.translate( -canvasRect.topLeft() );
            QwtPloarCurve::draw( &p, azimuthMap, radialMap, pole, radius, canvasRect );
        }

        painter->drawImage( canvasRect.topLeft(), m_image );
    }

    QImage m_image;
};

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};

[Tinou[FR]]

I'm trying to understand, is that a surcharge of the function draw to set the result in a Qimage?
The objective is to make a video from the 8000 image so I think to render temporary the image in a QImage or something else but I used a Qprocess (with mencoder) for the video so I need real images.
I don't no other way.
Clearly is that possible to render plot in a Qimage or something else and make a video, with what?

Thank you again for reply

[Tinou[FR]]

Hi all,
I'm sorry for the double post, but does anyone now how to reduce or optimise the renderer function ?
OR
How to create a video from the plot without save as file the image.