QBitmap is a Qt class used for masking/transparency in QPixmap. QBitmap is a class for containing monochrome (that is: each pixel is either on or off) images, instead of the colored Windows bitmaps.

The code below, adapted from Qt example 1: moving a sprite over a background in 2D, shows how to add transparency to a QPixmap.


#include <QGraphicsPixmapItem>



struct Sprite : public QGraphicsPixmapItem

{

  Sprite(

    const std::string& filename,

    const QColor& transparency_color = QColor(0,255,0)) //Lime green

  {

    QPixmap pixmap(filename.c_str());

    const QBitmap mask = pixmap.createMaskFromColor(transparency_color);

    pixmap.setMask(mask);

    this->setPixmap(pixmap);

  }

};

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(C++) QBitmap