Add jpg support for Qt::Pixmap on Windows

[stomar]

Creating a QPixmap with a jpg file does not work on Windows and results
in a null pixmap (on Linux it works just fine).

require 'Qt'
app = Qt::Application.new ARGV
Qt::Widget.new do
  pixmap = Qt::Image.new 'test.jpg'
  puts 'Null Pixmap'  if pixmap.null?  # => Null Pixmap
  puts Qt::ImageReader.supported_image_formats  # => bmp, pbm, pgm, png, ppm, xbm, xpm
end

System:

• Windows XP Professional
• Ruby 1.9.3-p125
• qtbindings 4.6.3.4 x86-mingw32

[kanfet]

Workaround:

1. Create 'plugins' folder in your application folder
2. Copy 'imageformats' folder to this 'plugins' folder from qtbindings gem, e.g. for me it is 'C:\RoR\RailsInstaller\Ruby1.9.3\lib\ruby\gems\1.9.1\gems\qtbindings-4.6.3.4-x86-mingw32\bin\plugins'
3. Add line after creating Qt::Application

app = Qt::Application.new ARGV
app.add_library_path('./plugins')

OR
You can just add line with correct path to 'plugins' folder in qtbindings gem

app = Qt::Application.new ARGV
app.add_library_path('path/to/gems/qtbindings/bin/plugins')

[kanfet]

Update to previous comment
Universal way:

app.add_library_path(Gem::Specification.find_by_name("qtbindings").gem_dir + '/bin/plugins')

[jmthomas]

The good news is that the current QtBindings built using the QT 4.8 works out of the box. When I run your program I get this for supported_image_formats:
bmp, gif, ico, jpeg, jpg, mng, pbm, pgm, png, ppm, svg, svgz, tga, tif, tiff, xbm, xpm

kanfet thanks for the workaround.

[stomar]

Since I am using the version from rubygems.org I am still using 4.6, but I am looking forward to the new version.

@ kanfet: Thanks a lot, your solution works like a charm.

[jmthomas]

Ryan just pushed the new 4.8.3.0 qtbindings gem. Let me know if this fixes your problem.

[stomar]

On the system mentioned on top the behaviour is still the same, even with qtbindings 4.8.3.0 x86-mingw32. But for me including the plugins path works fine.

[kybu]

JPG is still not supported out-of-box.

[ryanmelt]

After creating your application, you just need to add this line:

Qt::Application.instance.addLibraryPath(Qt::PLUGIN_PATH)

I will update the README.

[ghost]

Still not working, even after hardcoding the plugin path... JPEG SHOULD BE OUT OF THE BOX. No... plugins.. . these are known to be a pain in the ass! (for example: "windows plugin"... ahhhh)