QImage doesn't take in a JPG

[Rapidrain]

I have two photos, f1.bmp and f1.jpg each at 4608 x 3456 pixels

Using this I can see the photo appear in MyLabel derived from QLabel

QImage* image = new QImage();
image->load("D:\\Projects\\FridgeMagnets3\\src\\f1.bmp", Q_NULLPTR);
setPixmap(QPixmap::fromImage(*image));

the f1.bmp is enormous so it shows the upper left corner in my 600 x 450 MyLabel.

shrinking to f2.bmp (600 x 450) fits perfectly.

However a jpg of the very same photo (converted by PaintShopPro) never, never, ever
appears.

QImage* image = new QImage();
	bool b1 = image->load("D:\\Projects\\FridgeMagnets3\\src\\f1.jpg", "jpeg");
	if (b1 == true) {

		std::cout << "true " << std::endl;
	}
	else {
                // this guy always appears for *.jpg
		std::cout << "false " << std::endl;
	}
	setPixmap(QPixmap::fromImage(*image));

shrinking the jpg down to 600 x 450 or 595 x 446 or 500 x 375 doesn't help

Documentation says I need to write a const char* to indicate format.....I've tried "JPG" "jpg" "jpeg" and "JPEG".
nothing works!!!

How do I make QImage swallow a jpg??

[jsulm]

@Rapidrain Did you verify that this jpeg image is valid - open it in an image viewer?

[Rapidrain]

@jsulm : "open it in an image viewer" --- do you mean look at the picture with an app like MS Paint??

or do you mean use another class in Qt to ascertain its format????

[jsulm]

@Rapidrain I mean open it in any image viewer or MS Paint or whatever

[Rapidrain]

@jsulm I just tried it with

1. Fotos
2. Paint
3. Paint 3D
4. Paint Shop Pro 7

all show the image of f1.jpg

[jsulm]

@Rapidrain Some question:

1. How did you install Qt (is it your own build or precompiled binary)?
2. Not related to your problem: why do you allocate image on the heap using new operator (QImage image; would be enough)?

[J.Hilk]

@Rapidrain said in QImage doesn't take in a JPG:

QImage* image = new QImage();
	bool b1 = image->load("D:\\Projects\\FridgeMagnets3\\src\\f1.jpg", "jpeg");
	if (b1 == true) {

		std::cout << "true " << std::endl;
	}
	else {
                // this guy always appears for *.jpg
		std::cout << "false " << std::endl;
	}
	setPixmap(QPixmap::fromImage(*image));

your image is made with the jpg-codec but you tell QImage to use explicitly jpeg. I'm not 100% sure but I believe the headers are different.

Try it with the default probe/guess of the image format.

bool b1 = image->load("D:/Projects/FridgeMagnets3/src/f1.jpg");

[Rapidrain]

@jsulm

1. How did you install Qt (is it your own build or precompiled binary)?

my own build, 64 bit Qt

2. on the heap or local .... I am trying everything. As a local it doesn't work...As a new it doesn't work.

[Rapidrain]

@J.Hilk I have used "jpg" and "jpeg" and "JPG" and "JPEG" and none of them work

As you suggested, I left out the second argument completely and it still doesn't work.

I am compiling this with MinGW using Eclipse Neon

the Compile statements are :

15:15:53 **** Build of configuration Debug for project FridgeMagnets3 ****
MinGW32-make -f mf.Debug alld

1 create obj/Debug/FridgeMagnets3d.o
D:/MinGW/64/bin/g++ -c -g -std=gnu++11 -pipe -fno-keep-inline-dllexport -O0 -frtti -Wall -Wextra -fexceptions -mthreads -I'D:/Qt64/qt-install/include' -I'D:/Qt64/qt-install/include/QtWidgets' -I'D:/Qt64/qt-install/include/QtGui' -I'D:/Qt64/qt-install/include/QtCore' -I'D:/Qt64/qt-install/qtbase/include/QtWidgets' -I'D:/Qt64/qt-install/qtbase/include/QtGui' -I'D:/Qt64/qt-install/qtbase/include/QtCore' -I'D:/Projects/FridgeMagnets3/obj/Debug' -I'D:/Projects/FridgeMagnets3/src' -I'D:/Projects/FridgeMagnets3' -o obj/Debug/FridgeMagnets3d.o src/FridgeMagnets3.cpp

2a create obj/Debug/MyLabeld.o
D:/MinGW/64/bin/g++ -c -g -std=gnu++11 -pipe -fno-keep-inline-dllexport -O0 -frtti -Wall -Wextra -fexceptions -mthreads -I'D:/Qt64/qt-install/include' -I'D:/Qt64/qt-install/include/QtWidgets' -I'D:/Qt64/qt-install/include/QtGui' -I'D:/Qt64/qt-install/include/QtCore' -I'D:/Qt64/qt-install/qtbase/include/QtWidgets' -I'D:/Qt64/qt-install/qtbase/include/QtGui' -I'D:/Qt64/qt-install/qtbase/include/QtCore' -I'D:/Projects/FridgeMagnets3/obj/Debug' -I'D:/Projects/FridgeMagnets3/src' -I'D:/Projects/FridgeMagnets3' -o obj/Debug/MyLabeld.o src/MyLabel.cpp

2b create src/moc_MyLabeld.cpp
D:/Qt64/qt-install/bin/moc.exe -DUNICODE -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -D__GNUC__ -DWIN32 -I'D:/Qt64/qt-install/include' -I'D:/Qt64/qt-install/include/QtWidgets' -I'D:/Qt64/qt-install/include/QtGui' -I'D:/Qt64/qt-install/include/QtCore' -I'D:/Qt64/qt-install/qtbase/include/QtWidgets' -I'D:/Qt64/qt-install/qtbase/include/QtGui' -I'D:/Qt64/qt-install/qtbase/include/QtCore' -I'D:/Projects/FridgeMagnets3/obj/Debug' -I'D:/Projects/FridgeMagnets3/src' -I'D:/Projects/FridgeMagnets3' src/MyLabel.h -o src/moc_MyLabeld.cpp
2c create obj/Debug/moc_MyLabeld.o

D:/MinGW/64/bin/g++ -c -g -std=gnu++11 -pipe -fno-keep-inline-dllexport -O0 -frtti -Wall -Wextra -fexceptions -mthreads -DUNICODE -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -I'D:/Qt64/qt-install/include' -I'D:/Qt64/qt-install/include/QtWidgets' -I'D:/Qt64/qt-install/include/QtGui' -I'D:/Qt64/qt-install/include/QtCore' -I'D:/Qt64/qt-install/qtbase/include/QtWidgets' -I'D:/Qt64/qt-install/qtbase/include/QtGui' -I'D:/Qt64/qt-install/qtbase/include/QtCore' -I'D:/Projects/FridgeMagnets3/obj/Debug' -I'D:/Projects/FridgeMagnets3/src' -I'D:/Projects/FridgeMagnets3' -o obj/Debug/moc_MyLabeld.o src/moc_MyLabeld.cpp
3a create obj/Debug/DragWidgetd.o

D:/MinGW/64/bin/g++ -c -g -std=gnu++11 -pipe -fno-keep-inline-dllexport -O0 -frtti -Wall -Wextra -fexceptions -mthreads -I'D:/Qt64/qt-install/include' -I'D:/Qt64/qt-install/include/QtWidgets' -I'D:/Qt64/qt-install/include/QtGui' -I'D:/Qt64/qt-install/include/QtCore' -I'D:/Qt64/qt-install/qtbase/include/QtWidgets' -I'D:/Qt64/qt-install/qtbase/include/QtGui' -I'D:/Qt64/qt-install/qtbase/include/QtCore' -I'D:/Projects/FridgeMagnets3/obj/Debug' -I'D:/Projects/FridgeMagnets3/src' -I'D:/Projects/FridgeMagnets3' -o obj/Debug/DragWidgetd.o src/DragWidget.cpp
^
3c create obj/Debug/moc_MyLabeld.o
D:/MinGW/64/bin/g++ -c -g -std=gnu++11 -pipe -fno-keep-inline-dllexport -O0 -frtti -Wall -Wextra -fexceptions -mthreads -DUNICODE -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -I'D:/Qt64/qt-install/include' -I'D:/Qt64/qt-install/include/QtWidgets' -I'D:/Qt64/qt-install/include/QtGui' -I'D:/Qt64/qt-install/include/QtCore' -I'D:/Qt64/qt-install/qtbase/include/QtWidgets' -I'D:/Qt64/qt-install/qtbase/include/QtGui' -I'D:/Qt64/qt-install/qtbase/include/QtCore' -I'D:/Projects/FridgeMagnets3/obj/Debug' -I'D:/Projects/FridgeMagnets3/src' -I'D:/Projects/FridgeMagnets3' -o obj/Debug/moc_DragWidgetd.o src/moc_DragWidgetd.cpp

Link objects obj/Debug/FridgeMagnets3d.o obj/Debug/MyLabeld.o obj/Debug/moc_MyLabeld.o obj/Debug/DragWidgetd.o obj/Debug/moc_DragWidgetd.o
D:/MinGW/64/bin/g++ -Wl,-subsystem,windows -mthreads -o D:/Projects/FridgeMagnets3/bin/Debug/FridgeMagnets32d.exe obj/Debug/FridgeMagnets3d.o obj/Debug/MyLabeld.o obj/Debug/moc_MyLabeld.o obj/Debug/DragWidgetd.o obj/Debug/moc_DragWidgetd.o -LD:/Qt64/qt-install/lib -lglu32 -lopengl32 -lgdi32 -luser32 -lmingw32 -lqtmain -lQt5Widgets -lQt5Core -lQt5Gui

any libraries missing?

[jsulm]

@Rapidrain Your own build? That could explain your problem: you probably do not have the JPEG plug-in. Check the content of the plugins/imageformats directory of your Qt set-up.
If you compile Qt by yourself you should check the output of the configure command: it will tell your what is going to be built and what not.

[Rapidrain]

@jsulm the imageformats directory does (!) exist in the build. I found it last night. Now I wonder if I must include all of them in my compile and link statements, mention them in some manner.

My link command was :
g++ -Wl,-subsystem,windows -mthreads -o D:/Projects/FridgeMagnets3/bin/Debug/FridgeMagnets32d.exe obj/Debug/FridgeMagnets3d.o obj/Debug/MyLabeld.o obj/Debug/moc_MyLabeld.o obj/Debug/DragWidgetd.o obj/Debug/moc_DragWidgetd.o -LD:/Qt64/qt-install/lib -lglu32 -lopengl32 -lgdi32 -luser32 -lmingw32 -lqtmain -lQt5Widgets -lQt5Core -lQt5Gui

I copied the two files qjpeg.dll and qjpegd.dll into a directory imageformats and placed it next to the executable.
Then I changed the link command to :

g++ -Wl,-subsystem,windows -mthreads -o D:/Projects/FridgeMagnets3/bin/Debug/FridgeMagnets32d.exe obj/Debug/FridgeMagnets3d.o obj/Debug/MyLabeld.o obj/Debug/moc_MyLabeld.o obj/Debug/DragWidgetd.o obj/Debug/moc_DragWidgetd.o -LD:/Projects/FridgeMagnets3/imageformats -LD:/Qt64/qt-install/lib -lglu32 -lopengl32 -lgdi32 -luser32 -lmingw32 -lqtmain -lQt5Widgets -lQt5Core -lQt5Gui

Note that I added the imageformats directory as a source of libraries in the link command.

It didn't help though.

[jsulm]

@Rapidrain Sure it exists, but does it contain the JPEG plug-in? It should be named like libqjpeg.so
You do not have to add any of them to your compile/link config!
When deploying your app later you just need to make sure you deploy all needed plug-ins as well. See http://doc.qt.io/qt-5/linux-deployment.html

[Rapidrain]

@jsulm there is qjpeg.dll in the imageformats directory but ....
libqjpeg.so is nowhere on my computers.
I have used Qt for years and have countless versions here.
I have never seed libqjpeg.so

[jsulm]

@Rapidrain Sorry forgot that you're on Windows. qjpeg.dll is what you need.
Try to start your app with QT_DEBUG_PLUGINS environment variable set to 1 (you can add it in QtCreator Run settings of your project).

[Rapidrain]

@jsulm said in QImage doesn't take in a JPG:

QT_DEBUG_PLUGINS

I'm not using QtCreator

[jsulm]

@Rapidrain When do it wherever you're developing. If you start your app from a terminal:

QT_DEBUG_PLUGINS=1 && ./my_app

[Rapidrain]

@jsulm said in QImage doesn't take in a JPG:

QT_DEBUG_PLUGINS=1 && ./my_app

I tried what you suggested, it doesn't help.

[jsulm]

@Rapidrain Sorry, again forgot that you're on Windows:

set QT_DEBUG_PLUGINS=1
./my_app

[Rapidrain]

@jsulm said in QImage doesn't take in a JPG:

QT_DEBUG_PLUGINS=1

guess what?
It doesn't help.
Can you suggest a chain of options I must add to g++ when compiling and linking this code?

[jsulm]

@Rapidrain said in QImage doesn't take in a JPG:

Can you suggest a chain of options I must add to g++ when compiling and linking this code?

As I said before: there is no need to add any options to compiler/linker. The plug-ins are automatically loaded at runtime when needed. You either have some issues with your JPEG plug-in or with the picture you're trying to display. See http://doc.qt.io/qt-5/debug.html
After setting QT_DEBUG_PLUGINS your app should actually output a lot of text. Do you test a debug build?