Sorting Strategy

This is one of the core feature of BBOXHelper, its ability to order the blocks of text in a logial reading manner.

If you look at our Simple page layout, the middle block of text is a 2 column layout: you will read the first column then continue to the next column naturally without event thinking about it.

Well this is this natural reading order of things in a page, our default sorting algorythm tries to emulate. The implementation is done in the method named BBoxSort.contoursSort(...)

Default sorting Algorithm

It is the best algo I could came up with so far. Let me go through it a bit.

Ultimate Goal : Generate a rank for each block of text which we can sort upon, matching a certain natural reading order.

To generate a rank scoe, we need first to understand where the blocks stands.

Inspired by the following stackoverflow answer contributed by J-D, the default sorting algo implements the following tasks

First round: Vertical grouping

Find regions on the Y axis separated by empty regions: - Empty region is a region on the Y axis where there is no bounding boxes - By opposite we can then find regions on the Y Axis containing existing boxes See how blocks of text are grouped vertically like in the stackoverflow answer. For each non-empty region, - ascending sort on their opposite axis - add a sequence number to each belonging block + regularization value

I then repeat the same operation horizontally so I can handle the 2-columns of text locating on the same vertical group.

Second round: Horizontal grouping

Find regions on the X axis separated by empty regions: - Empty region is a region on the X axis where there is no bounding boxes - By opposite we can then find regions on the X Axis containing existing boxes For each non-empty region, - ascending sort on their opposite axis - add a sequence number to each belonging block + regularization value

At the end, each block has a rank which we can sort ascendantly.

This isn't perfect by all means, I'll be happy to receive feedback on this or welcome contributors to enhance this algorithm.

Others sorting algorithms

I'm providing few other "simplier" examples of sorting algorythm for convenience. Check the BBoxSort class in bboxutils.py.

Implement your own sorting algorithm

You can also implement your own algorithm defined as class method.

Define a class then function signature should be as follows

class myClass():
    @classmethod
    def mySort(cls,pageId,width,height,blocks):
        #...
        sorted=[]
        # Do your thing here with the incoming blocks
        #...
        return sorted

# Call the processing of your choice with the sortingAlgo parameter pointing to your own class
bboxresponse=BBoxHelper().processAzureOCRResponse(ocrresponse,sortingAlgo=myClass.mySort)