HDR Imaging - Exposure Compensation Tried HDR Algorithms of OpenCV. Since the algorithm takes pretty much time. I tried few alternative steps as follows.

Took sample images from: HDR Images

1. Divided the image into four equal regions as Top Left and Right, Bottom Left and Right
2. Estimated the brighter region and the darker region from the Highly exposed image by taking average of the regions respectively
3. Replaced the brighter region with the average of Low and Mid exposed image.
4. Replaced the darker region with the average of High and Mid exposed image.
5. Then merged the images back into a single image.
  
 Can someone suggest how to compensate the difference in them
 Tried Exposure Compensator of OpenCV but does not get expected result.
 
 The result image looks like:
Here is one idea:
Merge the HDR images per-pixel using known thresholds for saturation etc. The final image will have pixel values above 256. 

Apply a CLAHE (Contrast Limited Adaptive Histogram Equalization, its in OpenCV) to get the final image.

Often just doing the later will make your images look good.