Just let Qt do its work. If by drawing directly on QWidget you mean subclassing it and rewriting its Paint() method - don't do it unless you absolutely have to. Or, when you need to provide a delegate for a view. So far I've not had the necessity to dive that deep. And since you can display (and scale) images and videos using QLabel, push buttons can be readily supplied with an icon... I just had not need. Then again, your needs might differ.

Thank you all guys. Your suggestions and expert opinion helped a lot with solving the problem. QT forum is always so helpful. After trying many things here is the conclusion and code is now working perfectly fine I removed the tic toc part time(&start); timer = double(getTickCount()); tic(); It was working but crashing then just to make sure that QImage is not NULL I removed the img = QImage(); // releasing memory with if(!img.isNull()) img = QImage(); Its working perfectly fine now.

@Bonnie Thank you very much, it worked perfectly.

@Bonnie said in QfileDialog::Getopenfilename does not open the second time and after: Remove that static. Static local variables Variables declared at block scope with the specifier static or thread_local (since C++11) have static or thread (since C++11) storage duration but are initialized the first time control passes through their declaration (unless their initialization is zero- or constant-initialization, which can be performed before the block is first entered). On all further calls, the declaration is skipped. So with the static keyword, getOpenFileName will only be called at the first time. Thanks! I just realized that I should not have copy pasted that line of code without looking at it closer. Cheers.

Hi, How did you set the QLabel on your QScrollArea ? If you put it in a layout on the scroll area then that's wrong.

Rather than giving the pointer to your MainWindow instance, pass directly the pointer to your label. Basically: mainwindow->ui->label

Then maybe QTreeView::drawBranches is what you are looking for.

Thanks for the support guys. I tried making a transparent QPixmap image using Qt::transparent fill for the axis and overlaying it onto my other QPixmap, however it didn't work properly. So I ended up just drawing directly onto the image itself. Not the most efficient method but it seems to work...

@rjmoses Yes it will scale all images to match IconSize.

Hi, I got the expected output from grab(QRect) https://stackoverflow.com/questions/16362191/qt-grab-widget-and-save-image m_graphicsView->grab(rect).save("OUT.jpg"); Thanks all.

@mrjj Thanks for the help

@dheerendra Okay, done, thank you for reminding!

@mdma2 Can you post the full code of this short example, so that it can be tried out immediately using simple copy/paste...

@VRonin Yes, they are, but the pixmap is just grabbed QGraphicsView's content using grab() method.

I found where the problem was! As Christian Ehrlicher said according to the Documentation QByteArray::fromRawData() only store the pointer to the data. That explain why it doensn't work outside the function since the data goes out of scope. Instead of using this method I used one the constructors that make deep copy of the data. And it just works fine! QByteArray data (value.dataPointer (), value.dataSize ()); return data; Thanks all!

Hi, See my answer one the other thread.

Why create a QList and not do the conversion directly after calling CaptureImage ? Otherwise, does the library you are using to get the image provide a streaming API ?

Hi, Can you show how your create the image that you pass to the function ? Also, can you provide a stack trace of your application crash ?

Yes, a file with size 0 kb is being created

What do you think about this? int length = this->boundingRect().width(); length = (int)(((double)length * (double)value) / 100.0); QPixmap pix(this->boundingRect().width() - length, this->boundingRect().height()); pix.fill(Qt::transparent); QPainter p; p.begin(&pix); p.fillRect(pix.rect(), QColor(0, 0, 0, 120)); p.end(); gauge->setPixmap(pix); gauge->setPos(pos().x()+length, pos().y()); It works fine and the effect is the same as on example pixtures above.

I have find a way to get a QImage of an QWindow: Make a standard QWindow with is surface and add the following code: // set the current context OpenGL // check if an OpenGlContext is created QOpenGLContext context; context.setFormat(format()); if (!context.create()) qFatal("Cannot create the requested OpenGL context!"); context.makeCurrent(this); // init a new framebuffer QOpenGLFramebufferObjectFormat fboFormat; fboFormat.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil); fboFormat.setMipmap(true); fboFormat.setSamples(4); fboFormat.setTextureTarget(GL_TEXTURE_2D); fboFormat.setInternalTextureFormat(GL_RGB); resize(this->width(), this->height()); const QRect drawRect(0, 0, this->width(), this->height()); const QSize drawRectSize = drawRect.size(); _fbo = new QOpenGLFramebufferObject(drawRectSize, fboFormat); _fbo->bind(); ... _fboImage = new QImage(_fbo->toImage(false)); But, this is work only if the window is "visible", when it is set to Hidden the rendering of Qt3D was made (the rendering loop, because the GPU is used and the FPS is divided by 3), but the QOpenGLFramebufferObject was not filled :/ Do you have any idea of how force the filling of the fbo ? PS: I have found this here : http://stackoverflow.com/questions/17221730/do-offscreen-renderopengl-with-qt5

The QPixmap class has a constructor that takes a QSize parameter and therefore allows you to create a pixmap of a given size. That is what @jsulm is doing in the first line of his last code example. Documentation.

Hi, QPainter can draw a QImage. So you can for example create a new Widget, subclass for QLabel for example if you want and reimplement paintEvent. Like this you work all the time with your QImage without creating another one. And better you can only update the region that changed, no need to refresh everything. I did not try it but it should work. Sincerely

Hi! The way to convert your matrix to a QPixmap is to convert it to QImage first (e.g. using void QImage::setPixel(const QPoint &position, uint index_or_rgb)) and then convert the QImage to a QPixmap (using [static] QPixmap QPixmap::fromImage(const QImage &image, Qt::ImageConversionFlags flags = Qt::AutoColor)).

@kevin32 Great :)

@Rohith : thanks.but your solution does not work for me. I have multi button. I for example want to set image (/pic/1.png) to btn1 and then set another image to another button. My question How to set image to them in my code behind?

@SGaist Hi, I'm running Windows 10, OpenGL 4.5.0

hi As far as I know there is no build in raster to vector conversion. Also many images are not really good for it. Im wonder if QGraphicsScene is scaling images with best quality. http://stackoverflow.com/questions/22652491/qt-resize-image-with-best-quality

@hskoglund You were right! Thank you.

Thanks for the reply. This is using intel graphics, and unfortunately your workaround does not help. After your message, I've tested the same code from a newer live image and also on my more up-to-date laptop (which has similar hardware) and I can not reproduce the issue in either of these cases. On the affected machine, I tried updating the intel driver and mesa, but this did not solve it, so I guess it probably needs the kernel or qt packages updated as well. Unfortunately, this is not an option at this point. I've worked around the issue by re-implementing paintEvent() to do something like the following if (no_pixmap_set) { pos = calculateTextPosition() QPainter::drawText(pos, text); return; } QLabel::paintEvent(event); Which seems to work just fine. In fact, re-implementing the paintEvent has given me the chance to animate the image changes which looks pretty nice, and it will be easy to simplify the code a bit when all my machines are fully updated and the glitch is gone. Thanks again!

Thank you. Both worked though I guess it is supposed to be int w = ui->label->width (); int h = ui->label->height (); ui->label->setPixmap (pix.scaled (w,h,Qt::KeepAspectRatio));

@Matt-Chaput said: It seems odd for a moderator to be so belligerent, and act so condescending I'm sorry you feel that way but there's nothing I can do about it. I did try to provide a solution and explain why the other one was incorrect mathematically. Overlay mode would be useful for tinting e.g. icons with color, except it writes over transparent areas. That shortcoming of overlay mode is exactly the reason I suggested a two step approach instead. It breaks the problem into an alpha step and a color step. To be useful, it should multiply the alpha of the source and destination. If you wanted to do it in one step, yes. But, since there's no such mode in Qt, you can use the two step approach I suggested. First is the original. Second is the mask created using the alpha of the source (CompositionMode_SourceIn). Third is the final result using overlay with the mask (CompositionMode_Overlay). As far as I can tell this is the result OP wanted, so can you explain what I got wrong? There's nothing sensible about Qt is doing. Qt is providing a pretty common set of composition modes implemented by various APIs, described e.g. here, here and here. If you know of a graphics API that does SourceIn+Overlay in one step could you point us to it?

@EarthHobbit Hi This sample works for me (i can click it ) #include <QApplication> #include<QGraphicsScene> #include<QGraphicsDropShadowEffect> #include<QGraphicsPixmapItem> #include<QMessageBox> #include<QGraphicsView> class myGraphicsPixmapItem: public QGraphicsPixmapItem { public: myGraphicsPixmapItem(QPixmap pixmap): QGraphicsPixmapItem(pixmap) { }; ~myGraphicsPixmapItem() { }; void mouseReleaseEvent(QGraphicsSceneMouseEvent* event) { QMessageBox::information(NULL, "Information!", "Mouse release Detected!"); }; }; int main(int argc, char* argv[]) { QApplication app(argc, argv); QGraphicsScene scene; QPixmap pix(200, 200); QPainter* paint = new QPainter(&pix); paint->setPen(QColor(255, 34, 255, 255)); paint->drawRect(0, 0, 200, 200); myGraphicsPixmapItem* pixmapItem = new myGraphicsPixmapItem(pix); pixmapItem->setFlags(QGraphicsItem::ItemIsMovable); delete paint; QGraphicsView view(&scene); scene.addItem(pixmapItem); view.showFullScreen(); return app.exec(); }

@iamqt I agree. Since it will really depends on user machines. I use ramdisk for saving so it is very fast, where old hd will take a long time. Besides I user makes full HD animation with 1000 frames, I assume he do know it is a bit heavy :)

Printing out thumbnailData.data(), I get: 302 Found The resource was found at https://... So I realize my problem now. The thumbnail url is redirecting me to another url which is what I actually want to use to download for the QPixmap. Thanks for your help everyone.

You're welcome ! Since you have it working now, please update the thread title prepending [solved] so other forum users may know a solution has been found :)

ah ok. Good to know that it will (try) to scale an image to 0,0 :) Remember to flag as solved if your happy.

Just don't create it on heap. QPixmap is implicitly shared. It does not matter how you create pixmap. What does is total number of allocated resources. Changes to your code might fix something if your previous code did not clean the memory -did not delete pixmap. So code causing problem was not posted.