view image in a small part of window in qt

Question

I know how to view a image in the full window from Qt jpg image display but I need to display the image 200x300px size. that means I need the program to read the jpg image and rezise it and view it in a small box placed in the side of the window. I dont have eny idea which widget I should place for this and the method to do this. can somebody point out me some tutorial or give in simple advice.

thank you.

Nikos C. · Accepted Answer · 2012-12-14T17:33:28.147

3

After you load the image, for example:

QImage img;
img.loadFromData(data);

use QImage::scaled() to create a scaled copy of it and assign it to itself. Example:

img = img.scaled(200, 300, Qt::KeepAspectRatio, Qt::SmoothTransformation);

Adjust the flags as preferred (see the QImage::scaled() documentation on the available flags.)

You can then display it. The easiest way is to set it as a pixmap on a QLabel:

QLabel label;
label.setPixmap(QPixmap::fromImage(img));

You might want to set a fixed size for the QLabel, but this depends on how you handle your overall layout in your application.

edited Dec 14 '12 at 17:33

answered Dec 14 '12 at 17:17

Nikos C.

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@UmNyobe Welcome to the club ;-) – Nikos C. Dec 14 '12 at 17:22
I can add that fixing the size of the label may be required, otherwise re-sizing the window will re-size the label (thus the image displayed) – UmNyobe Dec 14 '12 at 17:25
@UmNyobe Can't QLabel::setScaledContents(false) be used for this? (Which is false by default anyway.) – Nikos C. Dec 14 '12 at 17:28
you are right with the image not being re-sized, but there is also layout issues. – UmNyobe Dec 14 '12 at 17:32
i replaced `img.loadFromData(data);` with `img.loadFromData("test.jpg"); now make it little more clear how to view it. – danial weaber Dec 14 '12 at 17:36
Im new in qt. I need help. what widget I should place to view the image in. – danial weaber Dec 14 '12 at 17:38
@LakshanPerera As written in the answer: a QLabel. – Nikos C. Dec 14 '12 at 17:39
I need the image appear on a button click. so I add the code in a slot function. is their a mistake. I get this error – danial weaber Dec 14 '12 at 17:51
error: request for member 'setPixmap' in '((MainWindow*)this)->MainWindow::.Ui::MainWindow::.Ui_MainWindow::label', which is of non-class type 'QLabel*' – danial weaber Dec 14 '12 at 17:51
@LakshanPerera You should read a Qt tutorial on how widgets work. I can't teach you Qt on StackOverflow :-/ – Nikos C. Dec 14 '12 at 17:56

view image in a small part of window in qt

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