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Thread: Loading static images (png, jpeg) using QImage

  1. #1
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    Default Loading static images (png, jpeg) using QImage

    I am using Visual Studio 2015 with 32-bit Qt libraries which i built from qt-everywhere-src-5.12.0. Trying to load a static image using QImage.
    Receive the following message when i debug :
    QImage not loading, Error : <Information not available, no symbols loaded for Qt5Gui.dll>

    I tried the same approach in Qt creator and I am able to load the image.

    Have used the following code :
    Qt Code:
    1. void BqtOglCanvas::drawImage(int width, int height, BmRect imageRect)
    2. {
    3.  
    4. imgFlag = true;
    5.  
    6. resultSize = QSize(width, height);
    7. paintRect = QRect(QPoint(imageRect.pnt1.x, imageRect.pnt1.y), QPoint(imageRect.pnt2.x, imageRect.pnt2.y));
    8. }
    9.  
    10. QImage* BqtOglCanvas::loadImage(const QString &fileName, QImage *image) {
    11.  
    12. image->load(fileName);
    13.  
    14. *image = image->scaled(resultSize, Qt::KeepAspectRatio);
    15.  
    16. return image;
    17. }
    18.  
    19. QImage BqtOglCanvas::getSourceImage() {
    20. return sourceImage;
    21. }
    22.  
    23. void BqtOglCanvas::paintEvent(QPaintEvent *e)
    24. {
    25.  
    26. if (imgFlag) {
    27. imgFlag = false;
    28.  
    29. QImage sourceImage = getSourceImage();
    30.  
    31. QImage* img = loadImage("C:/Users/qu826e/Downloads/ply.png", &sourceImage);
    32.  
    33. const QRect imageRect = paintRect;
    34. const QImage resImage = *img;
    35. QPainter painter(this);
    36. painter.drawImage(imageRect, resImage);
    37. }
    38. }
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    Any leads will be really helpful.

  2. #2
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    Default Re: Loading static images (png, jpeg) using QImage

    Receive the following message when i debug :
    QImage not loading, Error : <Information not available, no symbols loaded for Qt5Gui.dll>
    If you really are running a Debug version of your program, it should be reporting "Qt5GuiD.dll". Be sure you are linking with the correct libraries.

    QImage::load() returns a Boolean to indicate whether the load succeeded. Why don't you check it before trying to do anything more?

    Are you sure the fileName value points to the correct location on disk? Are you passing an absolute path or a relative path?

    Is a "image" a non-null pointer to a QImage? You can't call a class method through a null pointer, and "load" will not create a QImage instance.
    <=== The Great Pumpkin says ===>
    Please use CODE tags when posting source code so it is more readable. Click "Go Advanced" and then the "#" icon to insert the tags. Paste your code between them.

  3. #3
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    Default Re: Loading static images (png, jpeg) using QImage

    It's reporting Qt5Guid.dll. Have a doubt regarding the libraries. I built the lib using qt-everywhere-src-5.12.0 using the command : configure -debug -nomake examples -nomake tests -skip qtwebengine –opensource –opengl es2. Does this generate appropriate lib for QImage?

    QImage::load() returns a Boolean value true.

    fileName value points to the correct location on disk. it as an absolute path.

    QImage sourceImage = getSourceImage();
    sourceImage comes out to be null.

  4. #4
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    Default Re: Loading static images (png, jpeg) using QImage

    Quote Originally Posted by avinaskpai12 View Post
    QImage sourceImage = getSourceImage();
    sourceImage comes out to be null.
    Qt Code:
    1. QImage BqtOglCanvas::getSourceImage() {
    2. return sourceImage;
    3. }
    To copy to clipboard, switch view to plain text mode 

    Where do you fill this (member) variable?

  5. #5
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    Default Re: Loading static images (png, jpeg) using QImage

    Qt Code:
    1. void BqtOglCanvas::drawImage(int width, int height, BmRect imageRect)
    2. {
    3.  
    4. imgFlag = true;
    5.  
    6. resultSize = QSize(width, height);
    7. QImage image(resultSize, QImage::Format_RGB32);
    8. sourceImage = image;
    9. paintRect = QRect(QPoint(imageRect.pnt1.x, imageRect.pnt1.y), QPoint(imageRect.pnt2.x, imageRect.pnt2.y));
    10. }
    To copy to clipboard, switch view to plain text mode 

    filling the variable in drawImage.

  6. #6
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    Default Re: Loading static images (png, jpeg) using QImage

    You create an empty (uninitialized) image with the size width/height and assign it to sourceImage. Nothing more.
    Last edited by ChristianEhrlicher; 31st March 2020 at 15:11.

  7. #7
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    Default Re: Loading static images (png, jpeg) using QImage

    can you help me out with the steps to load the image?

  8. #8
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    Default Re: Loading static images (png, jpeg) using QImage

    It's pretty simple:

    Qt Code:
    1. QImage image;
    2. if ( image.load( filename ) )
    3. {
    4. // If you get here, the image was loaded successfully and is valid
    5. }
    6. else
    7. {
    8. // If you end up here, something went wrong
    9. }
    To copy to clipboard, switch view to plain text mode 
    <=== The Great Pumpkin says ===>
    Please use CODE tags when posting source code so it is more readable. Click "Go Advanced" and then the "#" icon to insert the tags. Paste your code between them.

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