Change the size of pixmap in a label

[metRo_]

Hi,
I creat a label and add a image to pixmap of label:
#include "mainwindow.h"
#include <QtGui>

MainWindow::MainWindow(QWidget *parent) :
QWidget(parent)
{
QHBoxLayout *lay=new QHBoxLayout;
setLayout(lay);
QImage image("comando.jpg");
QLabel *imageLabel = new QLabel(this);
lay->addWidget(imageLabel);
imageLabel->setPixmap(QPixmap::fromImage(image));
}

MainWindow::~MainWindow()
{

}
and now i want to resize the image. I want set a size to the label like 200*200 and resize the image to it.

[tbscope]

http://doc.qt.nokia.com/4.6/qimage.html#scaled-2

[metRo_]

#include "mainwindow.h"
#include <QtGui>

MainWindow::MainWindow(QWidget *parent) :
QWidget(parent)
{
QHBoxLayout *lay=new QHBoxLayout;
setLayout(lay);
QImage image("comando.jpg");
image.scaled(200,200,Qt::IgnoreAspectRatio,Qt::FastTransformation);
QLabel *imageLabel = new QLabel(this);
lay->addWidget(imageLabel);
imageLabel->setPixmap(QPixmap::fromImage(image));
qDebug() << imageLabel->pixmap()->size();
}

MainWindow::~MainWindow()
{

}
Thanks but it's still the same, the image load into the label with original size :S

[tbscope]

The Qt documentation is one of the best. I wonder why people don't read it.

Returns a copy of the image scaled to a rectangle with the given width and height

[metRo_]

you're right, thanks very much

[metRo_]

QPixmap QPixmap::scaled ( int width, int height, Qt::AspectRatioMode aspectRatioMode = Qt::IgnoreAspectRatio, Qt::TransformationMode transformMode = Qt::FastTransformation ) constHow can i use it?

even is i use like this: QSize tam(200,200);
imageLabel->pixmap()->scaled(tam,Qt::IgnoreAspectRatio,Qt::FastTransformation); it doesn't change the size of the picture, why i have to use the QImage scaled instead of it?

[tbscope]

What happens if you use:

imageLabel->setPixmap(QPixmap::fromImage(image.scaled(200,200)));

imageLabel->setPixmap(QPixmap::fromImage(image.scaled(200,200)));

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[metRo_]

it's work but this or that "image = image.scaled(200,200,Qt::IgnoreAspectRatio,Qt::Fas tTransformation);" is the same. i tallking about the scaled function for pixmap.

[metRo_]

it's work, but this is the same of "image = image.scaled(200,200,Qt::IgnoreAspectRatio,Qt::Fas tTransformation);".
Why i can't use the scaled function of pixmap.

[tbscope]

Who said you can't?

[metRo_]

i tried and the image doesn't resize! :S

[metRo_]

#include "mainwindow.h"
#include <QtGui>
 
MainWindow::MainWindow(QWidget *parent) :
QWidget(parent)
{
QHBoxLayout *lay=new QHBoxLayout;
setLayout(lay);
QImage image("comando.jpg");
QLabel *imageLabel = new QLabel(this);
lay->addWidget(imageLabel);
imageLabel->setPixmap(QPixmap::fromImage(image.scaled(400,400,Qt::KeepAspectRatio,Qt::FastTransformation)));
qDebug() << imageLabel->pixmap()->size();
}
 
MainWindow::~MainWindow()
{
 
}

#include "mainwindow.h"
#include <QtGui>

MainWindow::MainWindow(QWidget *parent) :
QWidget(parent)
{
QHBoxLayout *lay=new QHBoxLayout;
setLayout(lay);
QImage image("comando.jpg");
QLabel *imageLabel = new QLabel(this);
lay->addWidget(imageLabel);
imageLabel->setPixmap(QPixmap::fromImage(image.scaled(400,400,Qt::KeepAspectRatio,Qt::FastTransformation)));
qDebug() << imageLabel->pixmap()->size();
}

MainWindow::~MainWindow()
{

}

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Now all the time i want change the imagelabel i will need to set again the pixmap :s I resize the image all the time that the user will change the mainwindow size.

[dflo]

metRo_: Yes, that is true, whether you resize the image and extract its pixmap each time, or save the extracted pixmap and resize the pixmap each time. If the label can change size and you want the pixmap to change size with it, somebody has to resize the pixmap. In Qt, that somebody is you.

One option is to subclass QLabel and override the resizeEvent() method. Within that, resize the pixmap (from the original! don't keep resizing the resized image!), and call setPixmap(). So you probably want a setOriginalPixmap() method also, in case you want to change the image that's on the the label.

void setOriginalPixmap(QPixmap *pixmap)
{
  if (original_pixmap)
    delete original_pixmap;
  original_pixmap = pixmap;
  setScaledPixmap();
}
 
void resizeEvent (QResizeEvent *event)
{
  setScaledPixmap();
}
 
void setScaledPixmap (void)
{
  scaled_pixmap = original_pixmap->scaled(width(), height(), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
  setPixmap(scaled_pixmap);
}

void setOriginalPixmap(QPixmap *pixmap)
{
  if (original_pixmap)
    delete original_pixmap;
  original_pixmap = pixmap;
  setScaledPixmap();
}

void resizeEvent (QResizeEvent *event)
{
  setScaledPixmap();
}

void setScaledPixmap (void)
{
  scaled_pixmap = original_pixmap->scaled(width(), height(), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
  setPixmap(scaled_pixmap);
}

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[JohannesMunk]

@dflo: Welcome!

But this thread is quite old to be picked up, don't you think?

Joh

[dflo]

Yeah probably. I was looking for something else, and meanwhile I found some questions I could answer. Maybe metRo_ put his project on hold and will come back to it?

Thanks for the welcome!

[JohannesMunk]

Yeah :-> Just don't be disappointed if nothing happens - that's all I wanted to say.

Happy coding,

Johannes

[sonulohani]

First set the pixmap to the label.
Then, set the size of the label by:-

QLabel label=new QLabel;
label.setPixmap(pix);
label.setFixedSize(w,h);

QLabel label=new QLabel;
label.setPixmap(pix);
label.setFixedSize(w,h);

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