QPainter does not show up the image file

Prabu Subroto

20 Sep 2004 20 Sep '04

17:46

Dear my friends... I am using SuSE 9.1 and Qt 3.2 . I try this simple code: #include #include void pixForm::init(QPainter * p) { p->drawPixmap( 0,0, QPixmap("images/iamlagiajan.jpg"),0,0,100,100); } No problem in compiling. But if I run the compiled code, no picture showed up in the dialog form. Where is my mistake? Please tell me. Thank you very much in advance. __________________________________ Do you Yahoo!? New and Improved Yahoo! Mail - Send 10MB messages! http://promotions.yahoo.com/new_mail

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alan＠ibgames.com

20 Sep 20 Sep

19:06

New subject: [suse-programming-e] QPainter does not show up the image file

On 20 Sep 2004 at 10:46, Prabu Subroto wrote: Date sent: Mon, 20 Sep 2004 10:46:48 -0700 (PDT) From: Prabu Subroto To: suse-programming-e@suse.com Subject: [suse-programming-e] QPainter does not show up the image file

...

Dear my friends...

I am using SuSE 9.1 and Qt 3.2 .

I try this simple code: #include #include

void pixForm::init(QPainter * p) { p->drawPixmap( 0,0, QPixmap("images/iamlagiajan.jpg"),0,0,100,100); }

No problem in compiling. But if I run the compiled code, no picture showed up in the dialog form.

Where is my mistake?

Please tell me.

Thank you very much in advance.

Try turning it into a .png file (and don't forget to run qmake). Qt doesn't support .jpg out of the box... alan -- http://www.ibgames.net/alan Registered Linux user #6822 http://counter.li.org Winding Down - Weekly Tech Newsletter - subscribe at http://www.ibgames.net/alan/winding/mailing.html

Prabu Subroto

21 Sep 21 Sep

11:55

New subject: [suse-programming-e] QPainter does not show up the image file

Dear Alan... Firstly, thank you very much for your answer. I converted the image into png format with gimp 2.0 . I did the same like this: #include #include void pixForm::init(QPainter * p) { p->drawPixmap( 0,0, QPixmap("images/iamlagiajan.png"),0,0,100,100); } I compiled with... qmake -project qmake make no error message at all. but than if I run the compiled code, than it still does not the image file in the dialog form. Where is my mistake? Please...tell me. Thank you very much in advance. --- alan@ibgames.com wrote:

...

On 20 Sep 2004 at 10:46, Prabu Subroto wrote:

Date sent: Mon, 20 Sep 2004 10:46:48 -0700 (PDT) From: Prabu Subroto To: suse-programming-e@suse.com Subject: [suse-programming-e] QPainter does not show up the image file

...
Dear my friends...

I am using SuSE 9.1 and Qt 3.2 .

I try this simple code: #include #include

void pixForm::init(QPainter * p) { p->drawPixmap( 0,0, QPixmap("images/iamlagiajan.jpg"),0,0,100,100); }

No problem in compiling. But if I run the compiled code, no picture showed up in the dialog form.

Where is my mistake?

Please tell me.

Thank you very much in advance.

Try turning it into a .png file (and don't forget to run qmake). Qt doesn't support .jpg out of the box...

alan -- http://www.ibgames.net/alan Registered Linux user #6822 http://counter.li.org Winding Down - Weekly Tech Newsletter - subscribe at http://www.ibgames.net/alan/winding/mailing.html

-- To unsubscribe, email: suse-programming-e-unsubscribe@suse.com For additional commands, email: suse-programming-e-help@suse.com Archives can be found at: http://lists.suse.com/archive/suse-programming-e

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Stefan Hundhammer

11:51

New subject: [suse-programming-e] QPainter does not show up the image file

On Monday 20 September 2004 19:46, Prabu Subroto wrote:

...

void pixForm::init(QPainter * p) { p->drawPixmap( 0,0, QPixmap("images/iamlagiajan.jpg"),0,0,100,100); }

No problem in compiling. But if I run the compiled code, no picture showed up in the dialog form.

Where is my mistake?

You need to do that in a paint event, not at widget initialzation. You might want to read the first few chapters of a book about Xlib (e.g. http://www.amazon.com/exec/obidos/tg/detail/-/1565920023/ ) to learn why. CU -- Stefan Hundhammer Penguin by conviction. YaST2 Development SuSE Linux AG Nuernberg, Germany

Prabu Subroto

13:46

New subject: [suse-programming-e] QPainter does not show up the image file

Uffhh.... OK, I am going to buy the book. but at this moment, please help me to solve my problem. I have not understood how should I use QPaintEvent. All of the example code show this function in this form " void pixForm::paintEvent( QPaintEvent * event) ". Since I just want to make a try with "init()" (constructor) I don't understand how should the QPaintEvent implemented in my case. I just want if my program executed than the pixForm form appear, executes the constructor ( init() ), and finally the image file showed up in the dialog form (pixForm) . Please give me a very short example code, please... the example from trolltech is too complicated for me at this time. what does the QPaintEvent have to do with QPainter? I meant the relationship. I know from my book that QPaintEvent is a trigger but why I can not use init() to start the image file to be showed up. Thank you very much in advance. ==== #include #include #include void pixForm::init(QPaintEvent *, QPainter * p) { p->drawPixmap( 0,0, QPixmap("images/iamlagiajan.png"),0,0,100,100); } --- Stefan Hundhammer wrote:

...

On Monday 20 September 2004 19:46, Prabu Subroto wrote:

...
void pixForm::init(QPainter * p) { p->drawPixmap( 0,0, QPixmap("images/iamlagiajan.jpg"),0,0,100,100); }

No problem in compiling. But if I run the compiled code, no picture showed up in the dialog form.

Where is my mistake?

You need to do that in a paint event, not at widget initialzation. You might want to read the first few chapters of a book about Xlib (e.g.

http://www.amazon.com/exec/obidos/tg/detail/-/1565920023/

...

) to learn why.

CU -- Stefan Hundhammer Penguin by conviction. YaST2 Development SuSE Linux AG Nuernberg, Germany

-- To unsubscribe, email: suse-programming-e-unsubscribe@suse.com For additional commands, email: suse-programming-e-help@suse.com Archives can be found at: http://lists.suse.com/archive/suse-programming-e

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Stefan Hundhammer

22 Sep 22 Sep

09:33

New subject: [suse-programming-e] QPainter does not show up the image file

On Tuesday 21 September 2004 15:46, Prabu Subroto wrote:

...

I have not understood how should I use QPaintEvent. All of the example code show this function in this form " void pixForm::paintEvent( QPaintEvent * event) ".

Since I just want to make a try with "init()" (constructor) I don't understand how should the QPaintEvent implemented in my case.

I just want if my program executed than the pixForm form appear, executes the constructor ( init() ), and finally the image file showed up in the dialog form (pixForm) .

X doesn't work this way (come to think of it, neither does Win32). You don't actively begin painting on the screen, the windowing system tells your application when to do that - by sending an event. In X11 lingo this is called an "expose event" - which means that parts of your application's window (or all of it) are "exposed", i.e. either uncovered from windows that had been obscuring it, or simply displayed for the first time. In Qt this is mapped directly to the paintEvent() - a virtual function every QWidget has. Normally, you don't have to care about this, but if you want to do low-level drawing, this is your entry point. For your purposes (just displaying PNG or JPG graphics) you could also have used a QLabel with a QPixmap in it - I had suggested that earlier in this thread. It's basically like this: QLabel * imageViewer = new QLabel( parent ); QPixmap * pixmap = new QPixmap( "/wherever/mypixmap.png" ); imageViewer->setPixmap( pixmap ); But of course you can also derive your own custom widget class and do that yourself - by overwriting the paintEvent() virtual function and doing your own drawing there. Of course, you also have to take care of resizing your widget according to the pixmap's size (something QLabel also takes care of automatically).

...

Please give me a very short example code, please... the example from trolltech is too complicated for me at this time.

Too complicated?! http://doc.trolltech.com/3.3/showimg-example.html#x1260 void ImageViewer::paintEvent( QPaintEvent *e ) { if ( pm.size() != QSize( 0, 0 ) ) { // is an image loaded? QPainter painter(this); painter.setClipRect(e->rect()); painter.drawPixmap(0, menubar->heightForWidth( width() ), pmScaled); } } It doesn't get very much easier than this...

...

what does the QPaintEvent have to do with QPainter? I meant the relationship.

paintEvent() typically uses a QPainter to do the drawing.

...

I know from my book that QPaintEvent is a trigger but why I can not use init() to start the image file to be showed up.

X clients (applications) are not supposed to initiate drawing. They are supposed to do that upon receiving an expose event. Since the X protocol is a pretty complex client-server architecture, you might be lucky if you violate that convention, and sometimes it might even work out and your image might be displayed, but you might as well be not so lucky. I'd rather not rely on my luck too much in programming. ;-) -- Stefan Hundhammer Penguin by conviction. YaST2 Development SuSE Linux AG Nuernberg, Germany

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alan＠ibgames.com
Prabu Subroto
Stefan Hundhammer