Qpixmap of 32 bit Depth

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.

Code:

---

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 );

---

Please advice me..

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:

Code:

---

$ 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
...

---

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

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();

---

outputs

Code:

---

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

---

on Linux, Qt 4.7.2.

Hi Chris,

I did the same and found the properties of my image as below:

I think it doesnt have alpha : 8 bit

Code:

---

identify -verbose aegean-120km.png 
Image: aegean-120km.png                                
  Format: PNG (Portable Network Graphics)              
  Class: DirectClass                                   
  Geometry: 1292x1001+0+0                              
  Resolution: 37.79x37.79                              
  Print size: 34.1889x26.4885                          
  Units: PixelsPerCentimeter                           
  Type: TrueColor                                      
  Endianess: Undefined                                 
  Colorspace: RGB                                      
  Depth: 8-bit                                         
  Channel depth:                                       
    red: 8-bit                                         
    green: 8-bit                                       
    blue: 8-bit                                        
  Channel statistics:                                  
    red:                                               
      min: 0 (0)                                       
      max: 235 (0.921569)                              
      mean: 54.9768 (0.215595)                         
      standard deviation: 22.5171 (0.0883024)          
      kurtosis: 1.95082                                
      skewness: 0.869281                               
    green:                                             
      min: 3 (0.0117647)                               
      max: 243 (0.952941)                              
      mean: 74.8666 (0.293594)                         
      standard deviation: 21.6226 (0.0847946)          
      kurtosis: 1.41052                                
      skewness: 0.226536                               
    blue:                                              
      min: 1 (0.00392157)                              
      max: 241 (0.945098)                              
      mean: 93.5669 (0.366929)                         
      standard deviation: 31.2464 (0.122535)           
      kurtosis: -0.907665                              
      skewness: -0.429502
  Image statistics:
    Overall:
      min: 0 (0)
      max: 243 (0.952941)
      mean: 55.8526 (0.21903)
      standard deviation: 41.3977 (0.162344)
      kurtosis: -0.988763
      skewness: 0.0747025
  Rendering intent: Saturation
  Gamma: 0.45455
  Chromaticity:
    red primary: (0.64,0.33)
    green primary: (0.3,0.6)
    blue primary: (0.15,0.06)
    white point: (0.3127,0.329)
  Interlace: None
  Background color: rgb(1,1,1)
  Border color: rgb(223,223,223)
  Matte color: grey74
  Transparent color: black
  Page geometry: 1292x1001+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: Zip
  Orientation: Undefined
  Properties:
    date:create: 2011-05-19T10:17:37+06:00
    date:modify: 2010-11-29T18:15:51+06:00
    signature: e48cd3c45e0ab3014e55d9ae6f51de1d41f485add63ec622c074a58b31a39933
  Artifacts:
    verbose: true
  Tainted: False
  Filesize: 1.372mb
  Number pixels: 1.233mb
  Version: ImageMagick 6.5.4-7 2010-02-26 Q16 OpenMP http://www.imagemagick.org

---

I did the same of loading the PNG directly for me on both the cases it gives me a depth of 24 bit.....

Code:

---

true
QSize(1292, 1001) 24 false
QSize(1292, 1001) 24 false

---

Anything i have to try chris .....

---

Added after 26 minutes:

Hi chris,

I tried this, it sets my pixmap to 32 bit ......

Code:

---

overlay_map.load("/aegean-60km.bmp");
 
            qDebug() << overlay_map.size() << overlay_map.depth() << overlay_map.hasAlphaChannel();
 
            overlay_map.setAlphaChannel(QPixmap("/aegean-60km.bmp"));
 
            qDebug() << overlay_map.size() << overlay_map.depth() << overlay_map.hasAlphaChannel();

---

QSize(1292, 1076) 24 false
QSize(1292, 1076) 32 true

Now i didnt get any error .....This is the right way to set the pixmap to 32 Bit depth....

No, the right way would be to create a PNG file with an alpha channel in the first place. The setAlphaChannel() method is obsolete and likely to disappear.

If you really cannot supply a source image with an alpha channel then you could load it into a QImage and use QImage::convertToFormat()

Quote:

---

Originally Posted by ChrisW67

No, the right way would be to create a PNG file with an alpha channel in the first place. The setAlphaChannel() method is obsolete and likely to disappear.

If you really cannot supply a source image with an alpha channel then you could load it into a QImage and use QImage::convertToFormat()

---

OK Chris, i will follow the same ....

Thank you for your support Chris...:)