I'm trying to use pictureBox->Image (Windows Forms) to display a cv::Mat image (openCV). I want to do that without saving the Image as a file ('cause i want to reset the image every 100ms).
I just found that topic here: How to display a cv::Mat in a Windows Form application?
When i use this solution the image appears to be white only. I guess i took the wrong PixelFormat.
So how do figure out the PixelFormat i need? Haven't seen any Method in cv::Mat to get info about that. Or does this depend on the image Source i use to create this cv::Mat?
Thanks so far :)
Here i took a screen. Its not completely white. So i guess there is some color info. But maybe i'm wrong.
Screen
cv::Mat.depth() returns the pixel type, eg. CV_8U for 8bit unsigned etc.
and cv::Mat.channels() returns the number of channels, typically 3 for a colour image
For 'regular images' opencv generally uses 8bit BGR colour order which should map directly onto a Windows bitmap or most Windows libs.
SO you probably want system.drawing.imaging.pixelformat.Format24bppRgb, I don't know what order ( RGB or BGR) it uses but you can use the opencv cv::cvtColor() with CV_BGR2RGB to convert to RGB
Thanks for the help! The problem was something else.
I just did not allocate memory for the Image Object. So there was nothing to really display.
Using cv::Mat img; in the headerFile and img = new cv::Mat(120,160,0); in Constructor (ocvcamimg Class) got it to work. (ocvcamimg->captureCamMatImg() returns img).
Related
I would like to read DICOM images in C++ and manipulate them using opencv.
I managed to read a dicom image using DCMTK however, I am unsure how to convert it to an opencv Mat.
The following is what I have so far:
DicomImage DCM_image("test.dcm");
cv::Mat image(int(DCM_image.getWidth()), int(DCM_image.getHeight()), CV_8U, (uchar*)DCM_image.getOutputData(8));
which results in the following:
In a DICOM viewer, it looks as follows:
After normalising, the grayed image appears as follows:
Any help would be greatly appreciated.
The main problem I can see now is the difference of pixel value ranges (depths).
AFAIK, DICOM can have a rather big depth (16 bit), and you are trying to fit in into CV_8U, which is only 8 bit. You can get DicomImage instance's depth using DicomImage::getDepth(), and then create a cv::Mat with appropriate depth to hold your image data.
You may also need to normalize the data to maximally utilize you available range, so that the display with cv::imshow() would look as expected.
So:
Do DicomImage::getDepth() on your DCM_image
Create a cv::Mat with sufficient depth to hold your data
Scale, if necessary
Before calling DicomImage::getOutputData() on a monochrome DICOM image, you should make sure that you've selected an appropriate VOI transformation (e.g. Window Center & Width). This could be done by DicomImage::setMinMaxWindow(), DicomImage::setWindow() etc. See documentation of the DicomImage class.
Please note, however, that DicomImage::getOutputData() always returns rendered pixel data, i.e. not the original Pixel Data that is stored in the DICOM dataset.
U need to read the data type in DICOM image encoding an convert that to opencv type Mat. The opencv docs provides the entire information on their Mat header.
I've gotten an XImage object from XGetImage() from a screenshot, but now I don't know what to do with it. I'm using C++. Thanks.
The next best thing you could do, would be to use XPutImage() or use some other X11 image manipulation function.
Here you can find some examples, reading/changing some pixels, as well as a little more about the XImage data structure.
I would like to write CPP code that is able to take in a PNG file, scan through its pixels and identify where the transparent pixels are.
I tried doing this with CIMG, but it didn't work out as CIMG only supports the RGB channels. Even after installing image magick, the 4th channel is not giving me the right values.
Anyone can suggest a library I could use?
My platform is Windows. I didn't expect reading indexed palette image to be this difficult in C++. In case you are not familiar with it, it's single channel image but expresses its pixel color with 256 indexed colors called palette.
I was using OpenCV but its imread just converts the file to a 3 channel image so I have no way to save it back to indexed palette image or compare it with another indexed palette image.
I tried to use Bitmap but for some reason, it does not read correct pixel values.
So right now, I am looking for a light library or code to read pixels from indexed palette file.
Using OpenCV to read or write a image from real cameras will lose and change the image information, so I prefer to use gdi+, which is more powerful in dealing with image format problems to solve your problem.
As comments on the question shows, I decided to have two methods, OpenCV for non-indexed-palette images and Bitmap (GDI+) for indexed palette images. Now everything is working perfect.
I am capturing images in real time using OpenCV, and I want to show these images in the OGRE window as a background. So, for each frame the background will change.
I am trying to use MemoryDataStream along with loadRawData to load the images into an OGRE window, but I am getting the following error:
OGRE EXCEPTION(2:InvalidParametersException): Stream size does not
match calculated image size in Image::loadRawData at
../../../../../OgreMain/src/OgreImage.cpp (line 283)
An image comes from OpenCV with a size of 640x480 and frame->buffer is a type of Mat in OpenCV 2.3. Also, the pixel format that I used in OpenCV is CV_8UC3 (i.e., each pixel is 8-bits and each pixel contains 3 channels ( B8G8R8 ) ).
Ogre::MemoryDataStream* videoStream = new Ogre::MemoryDataStream((void*)frame->buffer.data, 640*480*3, true);
Ogre::DataStreamPtr ptr(videoStream,Ogre::SPFM_DELETE);
ptr->seek(0);
Ogre::Image* image = new Ogre::Image();
image->loadRawData(ptr,640, 480,Ogre::PF_B8G8R8 );
texture->unload();
texture->loadImage(*image)
Why I always getting this memory error?
Quick idea, maybe memory 4-byte alignment issues ?
see Link 1 and
Link 2
I'm not an Ogre expert, but does it work if you use loadDynamicImage instead?
EDIT : Just for grins try using the Mat fields to setup the buffer:
Ogre::Image* image = new Ogre::Image();
image->loadDynamicImage((uchar*)frame->buffer.data, frame->buffer.cols, frame->buffer.rows, frame->buffer.channels(), Ogre::PF_B8G8R8);
This will avoid copying the image data, and should let the Mat delete it's contents later.
I had similar problems to get image data into OGRE, in my case the data came from ROS (see ros.org). The thing is that your data in frame->buffer is not RAW, but has a file header etc.
I think my solution was to search the data stream for the beginning of the image (by finding the appropriate indicator in the data block, e.g. 0x4D 0x00), and inserting the data from this point on.
You would have to find out were in your buffer the header ends and where your data begins.