The best replacement for opencv is matlab.

The best alternatives to opencv are rated as following:
★★★★★  matlab
★★★★★  imagemagick
★★★★★  opengl
★★★★  opencv2
★★★  aforge
★★★  itk
★★★  pil
★★★  cimg
★★★  fastcv
★★  pcl
★★  javacv
★  imagej
★  emgu cv
  matlab image processing
  openframeworks
  simplecv

Your alternative for opencv is not listed? Suggest!
Speaking about opencv, one probably shouldn't forget about qt.

Other search terms related to opencv and their ratings are:
★★★★★ qt
★★★★★ ffmpeg
★★★★★ opencl
★★★ kinect
★★ cmake
★★ visual c++
★ visual studio 2010
★ openmp
★ ipp
★ matlab
processing
cuda
opengl
You have in mind a companion for opencv and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of opencv in all years. Click on graph for more.
opencv
matlab
imagemagick