I think you are referring to homography based stitching, you will need to do interpolation or inpainting to fill the holes or black pixels

well, my idea was using base64 algorithm, just select image or any point (x,y) you like and do encoding and decoding, this was the best (i think) to transfer image.

Did you use a mask?

In that case you can manually edit the mask. 

Check this link

http://stackoverflow.com/questions/31464912/black-lines-around-image-using-warpperspective-for-stitching-in-opencv