QT display image with Qlabel in layouts not working

Question

new to QT and I am planning to display images aligning beautifully with layouts.

I create 3 Qlabels and group them in vertical and horizontal layouts to construct a widget like:

<layout class="QHBoxLayout" name="horizontalLayout">
<item>
 <layout class="QVBoxLayout" name="verticalLayout">
  <item>
   <widget class="QLabel" name="label">
    <property name="text">
     <string>TextLabel</string>
    </property>
   </widget>
  </item>
  <item>
   <widget class="QLabel" name="label_2">
    <property name="text">
     <string>TextLabel</string>
    </property>
   </widget>
  </item>
 </layout>
</item>
<item>
 <widget class="QLabel" name="label_3">
  <property name="text">
   <string>TextLabel</string>
  </property>
 </widget>
</item>

in designer:

I use following to load my images and display images:

 ui->setupUi(this);
src=cv::imread("image2.bmp");
cvtColor(src,src,CV_BGR2RGB);
img = QImage((const unsigned char*)(src.data),src.cols,src.rows,src.cols*src.channels(),QImage::Format_RGB888);

ui->label->setPixmap(QPixmap::fromImage(img).scaled(ui->label->width(), ui->label->height(),Qt::KeepAspectRatio));

ui->label_2->setPixmap(QPixmap::fromImage(img).scaled(ui->label_2->width(), ui->label_2->height(),Qt::KeepAspectRatio));

ui->label_3->setPixmap(QPixmap::fromImage(img).scaled(ui->label_3->width(), ui->label_3->height(),Qt::KeepAspectRatio));

displaying image spans 480*640, and I choose to keep the aspect ratio. however, the program runs like this: pic lays in screen shots here

the image is resizing in a surprisingly wrong way. I have try Qt::KeepAspectRatiobyExpanding and Qt::ignoreAspectRatio but none of these behavior as expect.

Any idea about this?

Answer 1

You can set the image to fill the label with: -

void QLabel::setScaledContents(bool)

So call: -

ui->label->setScaledContents(true);
ui->label_2->setScaledContents(true);
ui->label_3->setScaledContents(true);

Also note that you can set the pixmap in the designer. Just add the images as a resource, then set it on the label, in its properties: -

Answer 2

I cannot see the images you've pasted, but perhaps the problem is based on the size of QLabels: what is their size prior to:

ui->label->setPixmap(QPixmap::fromImage(img).scaled(ui->label->width(), ui->label->height(),Qt::KeepAspectRatio));

Perhaps it's very small or just enough to hold the "TextLabel" string, hence the weird resizing?