This is an example of a code of vtk to read a jpeg image http://www.vtk.org/Wiki/VTK/Examples/Cxx/IO/JPEGReader or dicom file http://www.vtk.org/Wiki/VTK/Examples/Cxx/IO/ReadDICOM ,
when I run these projects, i can zomm the image with the right button of the mouse
however, in the code there is nothing in a direct relation with zoom or something like this, so there is something inside the classes
can anyone tell me how vtk can do this zoom because i need it in another project ?
Yes, certainly there is code inside the other classes. vtkRenderWindow, vtkRenderWindowInteractor, and vtkRenderer are all referenced by that sample. You can trace down the zooming code through those. https://github.com/Kitware/VTK/tree/master/Rendering/Core
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I have been searching around about this problem for awhile. I am making a cross platform program and I have figured out how to load an animated cursor with the windows API and how to create a cursor during run time from raw bitmap data. However I can't find good documentation for this for X11, for my Unix/Linux build of my program. I know I need to use the XRender extension functions, XRenderCreateCursor and XRenderCreateAnimCursor from this documentation https://www.x.org/releases/X11R7.6/doc/libXrender/libXrender.txt but I do not know how to use these functions and the documentation does now show any examples.
Also the raw image data is in the ARGB format, and I want to support the Alpha channel if possible with these cursors.
Could someone show me how to use the X11 and XRender (or XCursor) Library to create a cursor, static and animated, and possibly how to do it so the cursor can be used with any X11 window.
Thanks!
PS.
I am acually editing a open source libary for cross platfrom Gui that I am using for my program, and I am trying to add this feature into the libary but I am not used to programing with X11.
When it comes to X, nothing is simple.
First, review the specification of the X render extension.
The steps for creating an animated cursor are as follows.
First, you need to create a PICTURE for each frame of the animated cursor, using CreatePicture.
Use CreateCursor to create a CURSOR from each PICTURE. CreateCursor returns a CURSOR handle.
Then, you take the list of all CURSORs for all of the frames, and then use CreateAnimCursor to create a single CURSOR representing the animated cursor.
This all comes down to creating a PICTURE for each frame. A PICTURE is created using CreatePicture from a DRAWABLE and a PICTFORMAT. DRAWABLE would be the PIXMAP with the actual bitmask for the cursor's frame, and PICTFORMAT specifies which channels in the pixmap represent the red, color, and green channels, and must be one of the enumerated PICTFORMATs returned from QueryPictformat.
For more information, see the aforementioned X render extension specification.
Recently I have tried to do some graphics on the top of VLC video using vlc-qt (which provides a video widget). The approach was trying to draw something on the widget. But it failed duo to the fact that vlc-qt's widget uses an internal widget to render video. (See more details here)
Now I'm trying to do something different. I want to try drawing text (or some rectangles) on the VLC media itself (not the widget). I suppose it's the way how VLC media player renders subtitles (isn't it?)
So the question is this: Having a vlc-qt interface, how can I access underlying vlc object and draw something on it [using libVLC API]?
I'm afraid the only way to do it with libvlc is to use libvlc_video_set_callbacks + libvlc_video_set_format_callbacks. It will decode media stream's frames to memory, which you could use as you wish.
I have a small app that renders an image. It's in .ppm format and opens nicely in Mac's Xee image viewer. The image is created in the default project folder.
However, the user doesn't know where the image is after it is rendered and I would like to open it automatically or perhaps offer where to save the image before it is created.
That is the first problem. The second problem is .ppm - it's not opened by default on Windows, you need Irfan Viewer or something alike.
Is there a way to solve both those problems easily in Qt? For instance, the image is created where the user wants and my app displays it in that ppm format without using some other software? And If a user wants to reopen the image, I should probably make it possible, as well.
I am not a Qt, nor a C++ developer so I am struggling a bit with this, but I have to do it.
Thanks in advance for the tips and advices.
If you convert your image to a QImage (if it's not one already), you can specify where and in what format to save it when calling the QImage::save method.
OpenCV recently upgraded its display window, when it is used in Qt.
It looks very good, however I did not find any possibility for it to be embedded into an existing Qt GUI window. The only possibility seems to be the creation of a cvNamedWindow or cv::namedWindow, but it creates a free-floating independent window.
Is there any possibility to create that OpenCV window inside an existing GUI? All I could find on the OpenCV forums is an unanswered question, somewhat similar to my own.
There is a straight-forward possibility to show an OpenCV image in Qt, but it has two major problems:
it involves copying the image pixel by pixel, and it's quite slow. It has function calls for every pixel! (in my test application, if I create a video out of the images, and display it in a cvNamedWindow, it runs very smoothly even for multiple videos the same time, but if I go through the IplImage --> QImage --> QPixmap --> QLabel route, it has severe lag even for one single video)
I can't use those nice new controls of the cvNamedWindow with it.
First of all, the image conversion is not as inefficient as you think. The 'function calls' per pixel at least in my code (one of the answers to the question you referenced) are inlined by optimized compilation.
Second, the code in highgui/imshow does the same. You have to get from the matrix to an ARGB image either way. The conversion QImage -> QPixmap is essentially nothing else than moving the data from main memory to GPU memory. That's also the reason why you cannot access the QPixmap data directly and have to go through QImage.
Third, it is several times faster if you use a QGLWidget to draw the image, and I assume you have QT_OPENGL enabled in your OpenCV build. I use QPainter to draw the QPixmap within a QGLWidget, and speed is no issue. Here is example code:
http://sourceforge.net/p/gerbil/svn/19/tree/gerbil-gui/scaledview.h
http://sourceforge.net/p/gerbil/svn/19/tree/gerbil-gui/scaledview.cpp
Now to your original question: Your current option is to take the code from OpenCV, include into your project under a different namespace, and alter it to fit your needs. Apart from that you have no alternative right now. OpenCV's highgui uses its own event loop, connection to the X server etc. and it is nothing you can intercept.
My first guess is to want to say this: I'm sure that if you dig into the code for namedWindow, you will find that they use some sort of standard, albeit not oft-referenced, object for painting said window (that's in the openCV code). If you were ambitious enough, you could extend this class yourself, to interface directly to a frame or custom widget in Qt. There might even be a way to take the entire window and embed it, using a similar method of a Qt frame, or an extension of the (general) widget class. This is a very interesting question and relates rather directly to work I've been doing of late, so I'll continue to think about and research it and see if I can't come up with something else more helpful.
[EDIT] What specific new controls are you so interested in? It might be more efficient on the part of the programmer to extend a Qt control to emulate that, as opposed to my first suggestion.[/EDIT]
simply check out the opencv highgui implementation. as i recall it uses qt.
All,
I must have a fundamental neuron missing, but I cannot get a simple program to load a PNG file and display it in a window. I'm not sure if it is a QPixmap, a QPicture, or what. All of the samples in the QTCreator are a bit more than I need right now. Baby steps...
I can get the window to display, and the program doesn't barf when I try to load the PNG, but it never gets displayed.
If someone would post a simple program to load a PNG from a file and display it, it would greatly appreciated. (I know, asking a lot, but...).
Thanks!
:bp:
this example is minimal: http://doc.trolltech.com/4.6/widgets-imageviewer.html
You will want to have a look at the function ImageViewer::open():
Build a QImage object from a filename;
Convert your QImage to a QPixmap with QPixmap::fromImage();
Put your QPixmap in a QLabel with QLabel::setPixmap().
The QImage object will automatically chose an appropriate reader according to the format of the image it detects in step 1.