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Code: Alles auswählen

QImage *testbild = new QImage(2 * screen_i_half_side,2 * screen_i_half_side,QImage::Format_ARGB32);
    testbild->fill(Qt::transparent);

    QPainter *testpainter;
    testpainter = new QPainter();
    testpainter->begin(testbild);
    testpainter->setBackground(Qt::transparent);
    testpainter->setPen(QPen(line2_color, 2, Qt::DashLine, Qt::RoundCap, Qt::RoundJoin));
    testpainter->drawLine(0, 0, testbild->width(), testbild->height());  //Testlinie
    testpainter->setBrush(Qt::NoBrush);
    testpainter->eraseRect(QRectF(300, 300, 200, 100)); // in dieses Rechteck soll die Beschriftung geschrieben werden...
    testpainter->end();

    testbild->save("testbild.png", "PNG");

    painter->setCompositionMode(QPainter::CompositionMode_SourceOver);
    painter->drawImage(QPointF(-screen_i_half_side, 0), *testbild);

Code: Alles auswählen

#include <QImage>
#include <QPainter>

int main(int, char *[])
{
  QImage img(500,500,QImage::Format_ARGB32);

  QPainter p(&img);
  p.fillRect(img.rect(),Qt::green);

  // transparentes Rechteck erzeugen
  for (int x=50; x<100; x++)
    for (int y=50; y<100; y++)
      img.setPixel(x,y,Qt::transparent);

  p.setBrush(Qt::red);
  p.drawLine(0,0,200,200);

  img.save("test.png");
  return 0;
}