After I use opencv to identify rectangle will get the rectangle image of punctuation
I'll get the rectangle of punctuation as shown (red mark) in the picture on the X, Y coordinates


But when I image if disturbed
As is shown in


The lower right corner of the rectangular cannot identify

But I will have four rectangular known, and the proportion of four rectangular is ": : 1
"If I could have identified through three rectangular coordinates, the dynamic that last not identified rectangular coordinates are deduced to?