Archived:Transparent QPixmap picture

Comments

(no comments yet)

Log in or Join to leave comments.

Archived: This article is archived because it is not considered relevant for third-party developers creating commercial solutions today. If you think this article is still relevant, let us know by adding the template {{ReviewForRemovalFromArchive|user=~~~~|write your reason here}}.

Qt Quick should be used for all UI development on mobile devices. The approach described in this article (using C++ for the Qt app UI) is deprecated.

Article Metadata

---

Tested with

Devices(s): Nokia 5800 XpressMusic, Nokia N900

---

Compatibility

Platform(s): Qt

---

Article

Keywords: QPixmap, QPainter

Created: tepaa (21 Oct 2009)

Last edited: hamishwillee (11 Oct 2012)

Overview

This example shows how to change a QPixmap picture to transparent.

Preconditions

• Qt is installed on your platform.
  • Download Qt release from here: [1]
  • Qt on Maemo can be found here: Qt4 Maemo port

Header

private:
    // Original pixmap
    QPixmap pixmap;

Source

// Create new picture for transparent
QPixmap transparent(pixmap.size());
 
// Do transparency
transparent.fill(Qt::transparent);
QPainter p(&transparent);
p.setCompositionMode(QPainter::CompositionMode_Source);
p.drawPixmap(0, 0, pixmap);
p.setCompositionMode(QPainter::CompositionMode_DestinationIn);
// Set transparency level to 150 (possible values are 0-255)
// The alpha channel of a color specifies the transparency effect, 
// 0 represents a fully transparent color, while 255 represents 
// a fully opaque color.
p.fillRect(transparent.rect(), QColor(0, 0, 0, 150));
p.end();
 
// Set original picture's reference to new transparent one
pixmap = transparent;

Postconditions

The picture is now transparent.

See also

• QPainter