While trying to use OpenCV for face detection on Windows, I need to pull in almost all the libraries (2d, 3d, ml, gui etc.). Otherwise my program wouldn't run. I am not really sure why I need any GUI for something as algorithmic as object detection. What is the minimal set of libraries required and is there a special way to build OpenCV such that there aren't that many dependencies?
You need opencv_core to get base objects like cv::Mat, opencv_imgproc to use thresholds, histograms and other image pre-processing, and opencv_highgui for reading, writing and displaying images, and using video streams from cameras and video files. That's all I can tell you without knowing how to run openCV on Windows, and not knowing which version of openCV You are using. As far as I know there is no way of building only some parts of openCV.
Generally from my experience You only need to add libraries associated to headers which You are using. So, if you have problems with tracking them try to avoid using #include "opencv2/opencv.hpp" and try a bit harder way of #include "opencv2/core/core.hpp" etc.
Yes, you can build OpenCV without certain library features. OpenCV uses CMake, which requires a little learning if you don't know it already, but you can uncheck OpenCV components you don't need in the CMake build configuration.
You can get away without using highgui in your app if you can read images with some other library (but not sure if you can build OpenCV without it).
Also - you will need to #include "opencv2/objdetect/objdetect.hpp" for support of Haar cascade classifiers (as of OpenCV 2.3.1).
Related
I want to create a framework for automated rendering tests for video games.
I want to test an application that normally renders to a window with OpenGL. Instead, I want it to render into image files for further evaluation. I want to do this on a Linux server with no GPU.
How can I do this with minimal impact on the evaluated application?
Some remarks for clarity:
The OpenGL version is 2.1, so software rendering with Mesa should be possible.
Preferably, I don't want to change any of the application code. If there is a solution that allows me to emulate a X server or something like that, I would prefer it.
I don't want to change any of the rendering code. If it is really necessary, I can change the way I initialize OpenGL, but after that, I want to execute arbitrary OpenGL code.
Ideally, your answer would explain how to set up an environment on a headless Linux server that allows me to start arbitrary OpenGL binaries and render its output into images. If that's not possible, I am open for any suggestions.
Use Xvfb for your X server. The installation of Mesa deployed on any modern Linux distribution should automatically fall back to software rasterization if no supported GPU is found. You can take screenshots with any X11 screen grabber program; heck even ffmpeg -i x11grab will work.
fbdev/miniglx might be something that you are looking for. http://www.mesa3d.org/fbdev-dri.html I haven't used it so I have no idea if it works for your purpose or not.
Alternative is to just start and xserver without any desktop environment with xinit. That setup is using well tested code paths making it better suited for running your test. miniglx might have bugs which none has noticed because it isn't used everyday.
To capture the rendering output to images could be done with LD_PRELOAD trick to wrap glXSwapBuffers. Basic idea is to add your own swapbuffers function in between your application and gl library where you can use glReadPixels to download rendered frame and then use your favorite image library to write that data to image/video files. After the glReadPixels has completed you can call to library glXSwapBuffers to make swap happen like it would happen in real desktop.
The prog subdirectory has been removed from main git repository and you can find it from git://anongit.freedesktop.org/git/mesa/demos instead.
I'm toying around with constructing a basic music composition system for fun. I can represent music in memory, but I'd (obviously) like to be able to output actual sounds! I don't really care what the format is (MIDI, mp3, ogg, whatever). I just want to be able to load samples into the program and play them in the simplest way possible. I've searched around for a solution but everything I'm seeing is either a) too complex (overhead-wise) for my needs, b) not actively supported, or c) not well-documented. I would love to see an example of sound output or otherwise, some direction on the simplest way to do so.
You might like Euterpea, which isn't on Hackage but was a breeze to install and has quite verbose documentation (it seems it forms the core of an introductory Haskell course at Yale). Hover over the word "Euterpea" in the menu at the top to find more links/instructions.
I ended up using MIDI and sending events to SimpleSynth, on Mac OSX. This was achieved using the hmidi package and the bindings to OSX's CoreMIDI by bkomuves. I had to install a fork of the hmidi package from here to get it working with the latest GHC. I then installed SimpleSynth and enabled an IAC Driver using the Audio MIDI Setup utility on OSX. I then set SimpleSynth to listen from the IAC Driver I set up and was able to use the enumerateDestinations function from bkomuvres' bindings to CoreMIDI to grab the first available Destination and send MidiEvents from hmidi using send. It works like a charm!
With Haskell, you may wish to get a handle on the language fully by utilising other libraries/applications from your code, however the following link is a link to libraries for music and sound.
http://www.haskell.org/haskellwiki/Applications_and_libraries/Music_and_sound
Another idea is to gain familiarity with OpenAL with C/C++ and then from there you will have some familiarity with the structure of HOpenAL (Haskell binding of OpenAL which indeed calls the OpenAL DLL/SO).
Link with straightforward tutorial for OpenAL ago!
http://enigma-dev.org/forums/index.php?topic=730.0;wap2
I hope this helps...
This is a follow up to my previous question,
OpenCV PS 3 Eye
Can someone suggest a library that would allow me grab frames from camera without too much fuss (like video videoinput lib for windows) and pass them to opencv within my application?
I had a parallel problem using a completely different webcam: worked well in cheese/etc, v4l-info showed proper setup, but openCV would fail with:
HIGHGUI ERROR: V4L2: Pixel format of incoming image is unsupported by OpenCV
Unable to stop the stream.: Bad file descriptor
After much flailing I found that at least one guy had similar problems with webcams in various applications.
In blind faith I promptly punched in export LD_PRELOAD=/usr/lib/libv4l/v4l1compat.so and «poof» it worked.
The openCV v4l2 interface is not as robust as the v4l implementation and the export is a quick workaround (openCV appears to revert to v4l).
With a quick browse of opencv/modules/highgui/src/cap_v4l.cpp it would appear as though openCV would like to use v4l2.
I'm running Ubuntu Lucid 2.6.32-28-generic x86_64, libv4l-0 v0.6.4-1ubuntu1 with openCV pulled from the HEAD of the repo a few days ago.
In the course of explaining this I've resolved my issue. It turns out that openCV forces the resolution on a v4l2 device to 640x480 by default - and my device had a max 320x240 resolution which caused the fault when testing for the format type in opencv::highgui::cap_v41::try_palette_v4l2. I changed DEFAULT_V4L_WIDTH and, DEFAULT_V4L_HEIGHT.
I am writing an OpenGL game which will hopefuflly be for both linux and iphoneOS, I basically want to be able to build using the OpenGL ES 1.5 headers and run it on my linux desktop. Can I do this? IE, I want to only use the subset of API calls common between OpenGL and OpenGL-ES.
Doing the above and linking with normal libGL.a from my system gets me my screen but I seem to be able to do nothing but change the scene background colour.
I've done exactly that, and it worked well for me.
There are a bunch OpenGL|ES extensions that aren't available on standard OpenGL but very nice to have on a low spec platform. glDrawTexImage is such an extension. Emulating these extensions using a hand full of desktop OpenGL-calls is not a big deal though.
Also OpenGL|ES supports the fixed-point data-format for most entrypoints. Take glClearColorx for example. These aren't available for the desktop OpenGL, so you have to write a wrapper if you want to use them. It's a bit more work if you also store your vertex data in this format.
Oh - and note that OpenGL|ES does not come with the glu-library. You can use it on the desktop, but if you do you'll have to reimplement them later (see the 100 questions about gluLookAt and gluUnproject).
There is no such thing as OpenGL ES 1.5. Did you mean 1.1 ?
Also, how do you get a window ? This is platform specific.
In any case, you still should compile against the header that corresponds to the lib you will link against. You don't know for sure what the header sets up (e.g. on windows, which you don't care about but still, calling conventions are specified in there).
There are also some calls that don't map well between the 2. E.g. APIs that are only using doubles in GL are float in GLES (from the ES spec):
The double-precision only commands
DepthRange, Frustum, and Ortho are
replaced with single-precision or
fixed-point variants
So in short, there is a bit more work than just using the same code, although the work in question is still minimal if you stick to GL ES subset.
I woud like to create a cross-platform drawing program. The one requirement for writing my app is that I have pixel level precision over the canvas. For instance, I want to write my own line drawing algorithm rather than rely on someone elses. I do not want any form of anti-aliasing (again, pixel level control is required.) I would like the users interactions on the screen to be quick and responsive (pending my ability to write fast algorithms.)
Ideally, I would like to write this in Python, or perhaps Java as a second choice. The ability to easily make the final app cross-platform is a must. I will submit to different API's on different OS'es if necessary as long as I can write an abstraction layer around them. Any ideas?
addendum: I need the ability to draw on-screen. Drawing out to a file I've got figured out.
I just this week put together some slides and demo code for doing 2d graphics using OpenGL from python using the library pyglet. Here's a representative post: Pyglet week 2, better vertex throughput (or 3D stuff using the same basic ideas)
It is very fast (relatively speaking, for python) I have managed to get around 1,000 independently positioned and oriented objects moving around the screen, each with about 50 vertices.
It is very portable, all the code I have written in this environment works on windows and Linux and mac (and even obscure environments like Pypy) without me ever having to think about it.
Some of these posts are very old, with broken links between them. You should be able to find all the relevant posts using the 'graphics' tag.
The Pyglet library for Python might suit your needs. It lets you use OpenGL, a cross-platform graphics API. You can disable anti-aliasing and capture regions of the screen to a buffer or a file. In addition, you can use its event handling, resource loading, and image manipulation systems. You can probably also tie it into PIL (Python Image Library), and definitely Cairo, a popular cross-platform vector graphics library.
I mention Pyglet instead of pure PyOpenGL because Pyglet handles a lot of ugly OpenGL stuff transparently with no effort on your part.
A friend and I are currently working on a drawing program using Pyglet. There are a few quirks - for example, OpenGL is always double buffered on OS X, so we have to draw everything twice, once for the current frame and again for the other frame, since they are flipped whenever the display refreshes. You can look at our current progress in this subversion repository. (Splatterboard.py in trunk is the file you'll want to run.) If you're not up on using svn, I would be happy to email you a .zip of the latest source. Feel free to steal code if you look into it.
If language choice is open, a Flash file created with Haxe might have a place. Haxe is free, and a full, dynamic programming language. Then there's the related Neko, a virtual machine (like Java's, Ruby's, Parrot...) to run on Mac, Windows and Linux. Being in some ways a new improved form of Flash, naturally it can draw stuff. http://haxe.org/
QT's Canvas an QPainter are very good for this job if you'd like to use C++. and it is cross platform.
There is a python binding for QT but I've never used it.
As for Java, using SWT, pixel level manipulation of a canvas is somewhat difficult and slow so I would not recommend it. On the other hand Swing's Canvas is pretty good and responsive. I've never used the AWT option but you probably don't want to go there.
I would recommend wxPython
It's beautifully cross platform and you can get per pixel control and if you change your mind about that you can use it with libraries such as pyglet or agg.
You can find some useful examples for just what you are trying to do in the docs and demos download.