Rendering an image within QwtPlot

Hi all,

How can I attach an image file to QwtPlot as if it's a QwtPlotCurve so that I'll get to use the axis, legend, selection, zoom, etc ...

It seems that subclassing the QwtPlotRasterItem may be it, but I don't know how to override the renderImage method.

Code:

---

QImage OverlayImagePlot::renderImage(const QwtScaleMap &xMap, 
    const QwtScaleMap &yMap, const QwtDoubleRect &area) const
{
  //return QImage(_filename);
}

---

Thanks

I'm adding more information for clarity


How can I attach an image file, pix1.JPG, to QwtPlot as if it's a QwtPlotCurve so that I'll get to use the axis, legend, selection, zoom, etc ... see the attached image3.JPG

It seems that subclassing QwtPlotRasterItem, but I must haven't written the renderImage method correctly

Code:

---

QImage OverlayImagePlot::renderImage(const QwtScaleMap &xMap, 
    const QwtScaleMap &yMap, const QwtDoubleRect &area) const
{
  if ( area.isEmpty() )
        return QImage();
 
  QRect rect = transform(xMap, yMap, area);
 
  QPixmap pixmap(rect.width(), rect.height());
  pixmap.load(_filename);
 
  return pixmap.toImage();
}

---

Two problems that I'm facing:
1) the grid is drawn on top of the image, see pix4.JPG
2) when drawing this pix1.JPG on top of a QwtPlot that already contains a red standard curve and a blue custom rectangle [as in pix2.JPG snapshot] results in a very strange behavior: the red standard curve draws fine, but the blue custom rectangle disappeared (or being drawn behind the image) , pix3.JPG

QwtPlotRasterItem is for displaying raster data - something you don't have. In your case I would recommend to implement a special type of image item ( or combine it with your selection item ), where you simply do a QPainter::drawPixmap().

The painting order of depends on the z-value of the plot items.

Uwe

Hello, i have the same problem than ttvo

Quote:

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In your case I would recommend to implement a special type of image item ( or combine it with your selection item ), where you simply do a QPainter::drawPixmap().

---

Could you, please be more clear in your explanation Uwe?

Thanks in advance, and congratulations, Qwt jusks rocks ! ;)

In the examples you find implementations for some individual plot items. But probably the code of QwtPlotSvgItem should be enough ( strip the draw method down to a QPainter::drawPixmap ).

AFAIR I had already posted some code here or at the mailing list.

Uwe