Difficulties compiling OpenCV on Ubuntu ARM - opencv

I'm trying to compile OpenCV to use it on a ODROID-UX3 machine (ARM architecture) with Ubuntu 14.04. Following the guide on the OpenCV website I'm trying to install the cross compilation tools (gnueabihf) with no luck. Apt-get doesn't seem to locate the package gcc-arm-linux-gnueabihf. Is there a compatibility issue?

No, Ubuntu has a package named gcc-arm-linux-gnueabihf
here:
Package: gcc-arm-linux-gnueabihf (4:4.6.2-7) [universe]
The GNU C compiler for armhf architecture
Your problem is something else.

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libQGLViewer-2.7.2 qmake opengl

I'm trying to compile libQGLViewer-2.7.2
on linux amd64 debian qt5
using qmake, I got
Project ERROR: Could not find feature opengles2.
Any idea what's wrong? how can I debug this?
rhanks

Trouble building the ROS wrapper for the Intel RealSense camera

I am having trouble building the ROS wrapper for the Intel RealSense camera.
This is the error message I am seeing:
IOError: could not find ddynamic_reconfigure among message packages. Does that package have a on message_generation in its package.xml?
I am following the instructions here. I get the above error when I run this command:
catkin_make -DCATKIN_ENABLE_TESTING=False -DCMAKE_BUILD_TYPE=Release
I installed the RealSense SDK2.0 from the Debian Package. I verified the SDK install by running
realsense-viewer
I am working on ROS Kinetic, on Ubuntu 16.04
you need to add message_generation as build_depends in package.xml and in COMPONENTS in CMakeLists.txt.
Quick Look at their Github Showed The Answer

Using GPU in OpenCV

If I want to use my computer's GPU with OpenCV, is it necessary that I build OpenCV from source with CUDA enabled? Or can I install OpenCV with CUDA support via apt-get? I noticed the following 2 packages in apt-get:
libopencv-gpu-dev - development files for libopencv-gpu2.4v5
libopencv-gpu2.4v5 - computer vision GPU library
But I am not sure if these will work with OpenCV3 or if they are only compatible with OpenCV2. I know that the gpu module in Opencv2 was split up into multiple CUDA modules in OpenCV3.
Yes it is necessary that you build opencv from the source with CUDA option enabled. The apt-get packages won't work with OpenCV3 and above versions. I suggest you install the CUDA Toolkit first and then attempt installation of OpenCV or the GPU functions won't work.

Issue building OpenCV with ccache and CUDA

Trying to build OpenCV 3.3.1 with CUDA support, using ccache:
Ubuntu 16.04 LTS
OpenCV 3.3.1
CUDA 8.0
CCACHE 3.2.4
Make fails for .cu files, giving error:
/usr/bin/ccache: invalid option -- 'E'
Usage:
ccache [options] ...
I've added the /usr/lib/ccache to PATH, which cc and which c++ outputs /usr/lib/ccache/cc and /usr/lib/ccache/c++ respectively. Manually added a symlink for nvcc in /usr/lib/ccache directory, but now OpenCV CMakeLists.txt cannot find CUDA.
But interestingly I can build this sample CUDA code, with this CMake file without any issue.
I've searched the net and read most posts on SO and other forums, but had no success. I've had this issue for previous versions of OpenCV as well, but always disabled ccache as a solution.
Can someone please explain the reason behind this error?
Trying to set
-DCUDA_TOOLKIT_ROOT_DIR=/usr/local/cuda
seems to solve this problem for me.

Compiling OpenCV-contrib for IOS (especially the SFM-Module)

I've tried to install openCV_contrib for IOS, therefore I execute
python opencv/platforms/ios/build_framework.py "framework_dest"
on my Mac (I need Xcode for compiling openCV for IOS) but all the times, i got the message:
-- Checking SFM deps... FALSE
-- Module opencv_sfm disabled because the following dependencies are not found: Glog/Gflags
I need the SFM module, hence I tried installing Glog and Gflags at several ways: using
brew install glog gflags
and brew outputs, that those packages are successfully installed respective already installed.
Later I tried to compile both from GitHub on my own, but with no success, I'm still not able to compile SFM for IOS.
On Linux I could compile openCV including the SFM module, but I can't compile it for IOS, because Xcode is not available for Linux.
I don't know, what to do! Do some of you know how to install glog/gflags on Mac or do you know how to build the IOS-Framework of OpenCV on Linux or maybe how to build the IOS-Framework on my Mac using the binaries created with cmake .. && make in my Linux (because there SFM is compiled)?
There have to be some solution, because Mac is based on Linux, so if it works on Linux, why doesn't it work on my Mac?!
Thanks!

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