Qpixmap of 32 bit Depth

[augusbas]

Dear all,

One of my third party library needs a Qpixmap which should be of ARGB(32) format to enable the transparency. By default in Linux Qpixmap is of 24 bit depth.

I have tried the below method for conversion and passed the Qpixmap, and still it shows as 24 bit depth....How do i create a pixmap of 32 bit depth in Qt.

QImage overlay_image(768,768,QImage::Format_ARGB32);
 
            bool loaded = overlay_image.load ("/aegea.png",  0 );
 
            QPixmap overlay_map;
 
            overlay_map= overlay_map.fromImage ( overlay_image,Qt::AutoColor );

QImage overlay_image(768,768,QImage::Format_ARGB32);

            bool loaded = overlay_image.load ("/aegea.png",  0 );

            QPixmap overlay_map;

            overlay_map= overlay_map.fromImage ( overlay_image,Qt::AutoColor );

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Please advice me..

[ChrisW67]

What is the data in aegea.png, because it is this you are manipulating (you discard the unitialised Format_ARGB32 QImage)? Are you doing anything with the QImage other than loading the file? If not, then why not just load the QPixmap directly?

My example image is identified (ImageMagick) as:

$ identify -verbose plane.png
Image: plane.png
  Format: PNG (Portable Network Graphics)
  Class: DirectClass
  Geometry: 1040x138+0+0
  Resolution: 72x72
  Print size: 14.4444x1.91667
  Units: Undefined
  Type: TrueColorMatte
  Endianess: Undefined
  Colorspace: RGB
  Depth: 8-bit
  Channel depth:
    red: 8-bit
    green: 8-bit
    blue: 8-bit
    alpha: 8-bit
...

$ identify -verbose plane.png
Image: plane.png
  Format: PNG (Portable Network Graphics)
  Class: DirectClass
  Geometry: 1040x138+0+0
  Resolution: 72x72
  Print size: 14.4444x1.91667
  Units: Undefined
  Type: TrueColorMatte
  Endianess: Undefined
  Colorspace: RGB
  Depth: 8-bit
  Channel depth:
    red: 8-bit
    green: 8-bit
    blue: 8-bit
    alpha: 8-bit
...

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and is a mostly transparent banner of an aircraft with partial transparency of the spinning propeller. This code:

// Your code with adjustment for static method
    QImage overlay_image(768,768,QImage::Format_ARGB32); 
    bool loaded = overlay_image.load ("plane.png",  0 ); 
    QPixmap overlay_map = QPixmap::fromImage ( overlay_image,Qt::AutoColor );
    qDebug() << loaded;
    qDebug() << overlay_map.size() << overlay_map.depth() << overlay_map.hasAlphaChannel();
 
// Load the PNG directly
    overlay_map.load("plane.png");
    qDebug() << overlay_map.size() << overlay_map.depth() << overlay_map.hasAlphaChannel();

// Your code with adjustment for static method
    QImage overlay_image(768,768,QImage::Format_ARGB32); 
    bool loaded = overlay_image.load ("plane.png",  0 ); 
    QPixmap overlay_map = QPixmap::fromImage ( overlay_image,Qt::AutoColor );
    qDebug() << loaded;
    qDebug() << overlay_map.size() << overlay_map.depth() << overlay_map.hasAlphaChannel();

// Load the PNG directly
    overlay_map.load("plane.png");
    qDebug() << overlay_map.size() << overlay_map.depth() << overlay_map.hasAlphaChannel();

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outputs

true 
QSize(1040, 138) 32 true 
QSize(1040, 138) 32 true

true 
QSize(1040, 138) 32 true 
QSize(1040, 138) 32 true

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on Linux, Qt 4.7.2.