[Qt-interest] Difficulty creating Pixmaps

[Szalata, Zenon M.]

I hope that someone has time to read this lengthy note and help me with the following:

I am using QT 4.7.0 on RedHat Linux.
I have taken a few statements from the example qt/examples/painting/basicdrawing program
to create a simple test program, which I am using to learn how to display images from image files (jpeg and or png).  One of the image files, qt-logo.png, came with the example "basicdrawing" program.

My test program displays correctly the image from qt-logo.png file.  However, when I use a different file then no image is displayed.  I have used image files that I have created with GIMP or converted jpeg files to png with GIMP, they do not seem to work.  I have also taken the file
qt/examples/painting/imagecomposition/images/butterfly.png
and my test program does not work with it.
I have also taken the original qt-logo.png, converted it to qt-logo.jpg using GIMP.  This jpg file does not work.  I have then converted the qt-logo.jpg back to qtLogo.png using GIMP.  This new png file does not work either.  Also, this doubly converted png file is about 2.5 time the size of the original.  I don't understand why it is so much bigger than the original.  I am attaching some of the image files.

The test program is constructed by inserting an object of the RenderArea in a main window.

Here is the source code for the RenderArea class:

#include <QtGui>
#include "renderarea.h"

RenderArea::RenderArea(QWidget *parent): QWidget(parent){
  QString file1=":/images/qt-logo.png";
  QString file2=":/images/nlctaSketch.png";
  QString file3=":/images/21.png";
  QString file4=":/images/qt-logo.jpg";
  QString file5=":/images/button.png";
  QString file6=":/images/21.jpg";
  QString file7=":/images/place.jpg";
  QString file8=":/images/butterfly.png";

  pixmap1.load(file1);
  image1.load(file7);
//  pixmap1.fromImage( image1);

  setBackgroundRole(QPalette::Base);
  setAutoFillBackground(true);
  QRect rect=this->geometry();
  qDebug()<< "RenderArea:: rect = "<<rect;
  qDebug()<<"RenderArea:: pixmap size="<<pixmap1.size();
}
QSize RenderArea::minimumSizeHint() const{ return QSize(100, 100);}
QSize RenderArea::sizeHint() const{ return QSize(400, 200);}
void RenderArea::paintEvent(QPaintEvent * /* event */){

  QPainter painter(this);
  painter.drawPixmap(0,0,pixmap1);

  painter.setPen(palette().dark().color());
  painter.setBrush(Qt::NoBrush);
  painter.drawRect(QRect(0, 0, width() - 1, height() - 1));
}

Of all the files listed in the constructor only qt-logo.png gets painted in my test program.  Now, all these can be used successfully in a QLabel.  The size of the image which works is printed correctly when the program starts up.  The size for all the other images, which do not work, is printed as (-1,-1).  I could not find documentation which explains what that mean.  It probably means that the Pixmap is empty.

#ifndef RENDERAREA_H
#define RENDERAREA_H

#include <QBrush>
#include <QPen>
#include <QPixmap>
#include <QWidget>

class RenderArea : public QWidget{
  Q_OBJECT
public:
  RenderArea(QWidget *parent = 0);
  QSize minimumSizeHint() const;
  QSize sizeHint() const;

protected:
  void paintEvent(QPaintEvent*);

private:
  QPixmap pixmap1;
  QImage image1;
};
#endif

I am completely stuck on this, since I have no experience handling images in QT applications.

I will be grateful for any help, hints, etc.

Thanks,
Zen
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