imageformats plugins

[ht1]

Hi,

I followed the Qt centre instructions and I copied everything from QT's "plugins/imageformats" into my "C:/my_qt_compiling_directory/imageformats" and recompiled my program but still my program cannot handle image files. Do I need to make some changes to the project file? Or maybe I'm missing somethig else. Thanks.

[wysota]

It doesn't matter where the imageformats are when you compile the application. It matters where they are when you run it. If you run it on a computer that has Qt installed, they should work fine regardless where you place the application binary. When you deploy on another machine they have to be where the FAQ states.

[ht1]

Thanks Wysota,

When I run my program on a machine that doesn't have Qt installed and I put the image plugins in the folder suggested in the FAQ, they still don't function. Is there a way to statically link these plugins to my exe file during compilation somehow?

[wysota]

If you have their static versions compiled, then yes. But I suggest to take a look at why the plugins are not working for you. Verify it is really related to the plugins by loading a PNG image that doesn't use a plugin. Do it exactly the same way you do for other images. At best just replace a ".jpg" with ".png" in your application code and replace the JPEG image with a PNG one.

[ht1]

Thansk again, Wysota,

I know that my program is OK because it works with BMP (and not with TIFF, GIF or JPG) images on the computer that does not have Qt4 installed and it works with all images on the computer that has Qt4 installed.

How could I obtain/compile static versions of the imageformats dll files. Linking them to my exe seems like the best solution to me.

[wysota]

Thansk again, Wysota,

I know that my program is OK because it works with BMP (and not with TIFF, GIF or JPG) images on the computer that does not have Qt4 installed and it works with all images on the computer that has Qt4 installed.

What does this small program return on either of the machines?

#include <QtGui>
#include <QtDebug>
 
int main(int argc, char **argv){
  QApplication app(argc, argv);
  foreach(const QByteArray &fmt, QImageReader::supportedImageFormats()){
    qDebug() << QString(fmt);
  }
  return 0;
}

#include <QtGui>
#include <QtDebug>

int main(int argc, char **argv){
  QApplication app(argc, argv);
  foreach(const QByteArray &fmt, QImageReader::supportedImageFormats()){
    qDebug() << QString(fmt);
  }
  return 0;
}

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How could I obtain/compile static versions of the imageformats dll files. Linking them to my exe seems like the best solution to me.

You need to reconfigure and rebuild Qt. configure -help will show you the proper options.

[ht1]

Hi Wysota.

I ran your test program on the machine that has Qt4 but I did not detect anything happening at all. Is this program supposed to list the file extentions supported?

In order to compile imageformats dll files I have to reconfigure Qt in on my computer??That sounds a bit complicated for my current knowledge but I'd like to try it. Are there any step by step instructions available?

[wysota]

I ran your test program on the machine that has Qt4 but I did not detect anything happening at all.

Add CONFIG+=console to the project file, rerun qmake and rebuild the project.

Is this program supposed to list the file extentions supported?

Yes.

In order to compile imageformats dll files I have to reconfigure Qt in on my computer??

Yes.

That sounds a bit complicated for my current knowledge

So use the shared versions. They are much less complicated and you still haven't verified they are the ones causing trouble. Do that first before trying more tedious options like the one below.

Are there any step by step instructions available?

configure -help then configure <your set of switches go here> and then mingw-make or whatever your make command is.

[ht1]

Thanks again, Wysota, I got your test program to work now.

The computer that does not have Qt4 recognizes bmp, pbm, pgm, png, ppm, xbm, xpm as image files. The list is not getting longer when I put all the Qt image dll files in the "imageformats" folder.
The computer that has Qt4 recognizes all 14 file formats as image files.
So, what's your professional verdict? What do you think could be wrong? Many thanks!

[jacek]

The list is not getting longer when I put all the Qt image dll files in the "imageformats" folder.

Could you post the full paths to that folder and the executable? Is that application compiled in release mode?

[wysota]

So, what's your professional verdict?

My professional verdict is that your image plugins are not loaded.

What do you think could be wrong?

You are probably mixing debug and release mode files, you have missing dependencies or your paths are incorrect. I suspect Jacek will want to suggest at least one of the three right after you answer his questions.

Oh, and I'd like to add one more question to his few - Could you list the exact file names of Qt libraries you have deployed on the target machine?

[ht1]

Wysota and Jacek, your recommendations were very good and I was able to get my program to work. Thanks! Mixed up paths was the problem.

I'd like to pursue trying to put everytihing (all the dll files) into one exe file. I understand that I have 2 options:
1) reconfigure my mingw
2) obtain static versions of these dll files

I played with reconfiguring and did not get very far. I am not sure what the configuration options are that I need to use. Has anybody recently done this with mingw? I'd be very thankful for your help.
The second question is about obtaining these static versions of the dll files. How?

[banzai.ed]

I have this problem before and it can fixed below:

1. Assuming your program is in c:\myapp
2. Copy imageformats folder in your program folder: c:\myapp, and you can just keep those dlls you really need.
3. Add library path right after the initiation of the qApplication

Should be OK

[wysota]

I played with reconfiguring and did not get very far. I am not sure what the configuration options are that I need to use. Has anybody recently done this with mingw?

The essential switch is "-static".

The second question is about obtaining these static versions of the dll files. How?

They are not distributed anywhere.

[ht1]

Banzai.ed, thanks!

I am a bit unclear how you do this:

3. Add library path right after the initiation of the qApplication

Do you just type in your main functions something like

c:/myapp/imagefomats

c:/myapp/imagefomats

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This won't compile.

[jpn]

He was talking about QCoreApplication::addLibraryPath().

[ht1]

JPN, thanks for your clarification.
So it looks like this is the way to add a library path?

QString myPath;
myPath = "c:/Qt/myapp/imageformats";
application.addLibraryPath(myPath);

QString myPath;
myPath = "c:/Qt/myapp/imageformats";
application.addLibraryPath(myPath);

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It looks like this achieves that my DLL's can be in any folder I want to put them but I still have to have separate DLL's to make my program run. I'd really like to figure out how to statically link DLL's to my executable using mingw.

[jpn]

You'd start with building static version of Qt and its plugins. See our wiki for more details: [WIKI]Building static applications[/WIKI]. Make sure you pay attention to configure output. It will inform you about plugins being built. Once you have succeed building a static Qt + plugins, you will have to import static plugins to your app: Static Plugins.

[ht1]

JPN, that was a very useful link, thanks.

I got my Qt rebuilt and it now makes exe files that are idependent of mingw DLL's and that part is great.

But when I try to use Qt plugins as explained in http://doc.trolltech.com/4.3/plugins-howto.html (I updated both main.cpp and myproject.pro as suggested in tutorial), the compiler gives me error message "can't find -lqjpg". This means it cannot find the static plugin. How do I make the compiler find it? Where is this file located? Do I need to put it in the same folder with my main.cpp when I compile? Is there more to compiling in the static mode than just typing "make" at my mingw prompt (this is all I did back when I used DLL's)?

[wysota]

Did you configure Qt to build static plugins? Do you have them after the built is complete?