modify background images and a backward view

Author: wangyida

modules/README.md

@@ -47,7 +47,7 @@ $ cmake -D OPENCV_EXTRA_MODULES_PATH=<opencv_contrib>/modules -D BUILD_opencv_re
 19. **opencv_xfeatures2d**: Extra 2D Features Framework containing experimental and non-free 2D feature algorithms.
 
 20. **opencv_ximgproc**: Extended Image Processing: Structured Forests / Domain Transform Filter / Guided Filter / Adaptive Manifold Filter / Joint Bilateral Filter / Superpixels.
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 21. **opencv_xobjdetect**: Integral Channel Features Detector Framework.
 
 22. **opencv_xphoto**: Additional photo processing algorithms: Color balance / Denoising / Inpainting.