QImage and scaling problems

Kris Revi

This is my code

void MainWindow::on_BUTTON_SELECTIMAGE_MATRIX_clicked()
{
    // Open QFileDialog and store the path in fileName
    QString filePath = QFileDialog::getOpenFileName(this, tr("Open Image"), "c\\",
                                                          tr("Image Files (*.png *.jpg *.bmp)"));

    ui->TEXT_IMG_PATH->setText(filePath); // Display the path to the image selected

    imageObject = new QImage();           // Make a new imageObject
    imageObject->load(filePath);          // Load the image from path

    if(!filePath.isEmpty())               // Check to see that a image is selected and stored in fileName
    {
        QFile f(filePath);
        QFileInfo fileInfo(f.fileName());
        QString filename(fileInfo.fileName());

        imageHandler(imageObject, filename);        // Send the Image for processing
    }
}

void MainWindow::imageHandler(QImage *img, QString fileName)
{
    if(img->size() == QSize(32, 32))
    {
        qDebug() << "[IMAGEHANDLER][INFO] 1. Image is 32x32";
    }
    else
    {
        qDebug() << "[IMAGEHANDLER][INFO] 1. Image is NOT 32x32";
        qDebug() << "[IMAGEHANDLER][INFO] 2. Resizing Image to 32x32";

        img->scaled(32, 32, Qt::KeepAspectRatio, Qt::SmoothTransformation); // Scale the image down to 32x32
    }

    QImage img2{32, 32, QImage::Format_RGB16}; // The image is stored using a 16-bit RGB format (5-6-5).
    img2.fill(QColor(Qt::black).rgb());        // Fill the new image with a black background (needs to be filled to get the correct color data)
    QPainter painter(&img2);                   // Prepare new image for painting
    painter.drawImage(0, 0, *img);             // Paint the original image onto the new image
    img2.save(fileName);                      // Save that fucker and lets move on

    // Get the color 16bit (5-6-5) color data and put it in a QVector and prepare for sending to ESP32
    QVector<quint16> RGB565;
    RGB565.reserve(img2.width() * img2.height());
    for(int y = 0; y < img2.height(); y++) {
        const quint16 *line = reinterpret_cast<const quint16*>(img2.constScanLine(y));
        for(int x = 0; x < img2.width(); x++)
            RGB565 << *(line++);
    }
}

Original Picture

what i get

so what am i doing wrong? (the size of the image is 32x32 and alpha channel is removed and replaced with a black background! that is correct! however as you can see in the right bottom corner you see alittle red from marios hat so the image did not get scaled down)

VRonin

@Kris-Revi said in QImage and scaling problems:

img->scaled(32, 32, Qt::KeepAspectRatio, Qt::SmoothTransformation);

scaled() is const. it doesn't change the image but return a copy of the image scaled.