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  1. Qt
  2. QTBUG-16033

OpenGL paint engine fails to render images bigger than the maximum texture size

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Details

    • Bug
    • Resolution: Done
    • P2: Important
    • 4.7.2
    • 4.7.1
    • None
    • Maemo 5, N900 sw20.2010.36-3.203.1
    • 69ed34d2aa77a3bacc7f66797baa514f35358b7e

    Description

      When trying to use QPainter and OpenGL graphics system to draw a QImage with dimensions bigger than the maximum texture size in N900 (2048x2048), the result is either no output at all (black rectangle), or severe artifacts (only some sub-tiles are rendered).

      QOpenGLPaintEngine::drawImage() should be able to partition/scale the image down to the max. supported texture size, but this doesn't seem to work on Maemo platform. Same applies to drawPixmap().

      Simple test application to reproduce the issue:

      #include <QApplication>
      #include <QPaintEngine>
      #include <QImage>
      #include <QPainter>
      #include <QWidget>
      
      class Widget : public QWidget
      {
          Q_OBJECT
      public:
          Widget(QWidget* parent = 0);
      
      protected:
          void paintEvent (QPaintEvent* event);
      
      private:
          QImage m_image;
          int m_imgWidth;
          int m_imgHeight;
      };
      
      Widget::Widget(QWidget* parent)
          :QWidget(parent),
          m_imgWidth(2560), // fails to render if width or height > 2048
          m_imgHeight(1440) 
      {
          QRect rect(0, 0, m_imgWidth, m_imgHeight);
          m_image = QImage(rect.size(), QImage::Format_RGB32);
      
          QPainter painter(&m_image);
          QColor color(200, 240, 160);
          QBrush brush(color);
          painter.setBrush(brush);
          painter.setPen(color);
          painter.drawRect(rect);
      
          // draw a checkerboard pattern on image
          color = QColor(240, 160, 200);
          brush.setColor(color);
          painter.setPen(color);
          painter.setBrush(brush);
          int length = 157;
          int y = 0;
          int c = 0;
            while(y*length+length < m_imgHeight) {
              int x = c % 2;        
              while(x*length+length < m_imgWidth) {
                  rect.setCoords(x*length, y*length, x*length+length, y*length+length);
                  painter.drawRect(rect);
                  x +=2;
              }
              ++y;
              ++c;
          }
      }
      
      void Widget::paintEvent(QPaintEvent* event) {
          Q_UNUSED(event)
          QPainter painter(this);
          QRect imageRect(20, 20, m_imgWidth/1.3, m_imgHeight/1.3);
          // draw image scaled to widget's size
          painter.drawImage(contentsRect(), m_image, imageRect);
      }
      
      #include "main.moc"
      
      int main(int argc, char **argv)
      {
          QApplication::setGraphicsSystem("opengl");
          QApplication a(argc, argv);
      
          Widget w;
          w.resize(800, 400);
          w.show();
          
          return a.exec();
      }
      

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            rodal Samuel Rødal
            treinio Topi Reiniö
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            Dates

              Created:
              Updated:
              Resolved:

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