Exporting Image Labels in .json format

[mcanset]

Hello everyone,

I am trying to use the KNIME image processing tools and would like to extract the labels that I created after using node connected component analysis. Is there a way to export input images+annotations as something like collections etc. ? My second question if exporting is possible then, could we export the labels in coco json or json format?

Thanks in advance,

[LukasS]

Hi @mcanset and welcome to the community!

There are in fact multiple ways of exporting your labels - it depends on what you want to do with them. Exporting the labels as json will hardly work, as a json is basically a string representation - you can think of using the base64 representation, but I doubt this is what you really want.

I would probably go with a Segmennt Features node after the Connected Component Analysis. Besides calculating all kinds of interesting features of each label, it gives the labels as a bitmask. The Bitmasks you can save to disk with an Image Writer and the rest of the table you can convert to a json with the Table to JSON and write with a JSON Writer.

But as said, it depends a little bit on what you intend to do with the data afterwards - could you elaborate on that? Maybe there is a more fitting solution.

Kind regards,
Lukas

[mcanset]

Hello Lukas,

Many thanks for the quick response. I want to use knime for labeling purposes for my training data and the reason why i choose knime is that its capability of image pre-processing.I use some other nodes before connected component analysis to reduce noise, applying threshold etc.
I followed your description and it works. I guess the same applies also for yolo format, but with .csv writer and then i need to convert it to .txt format.
My last question is that which node should i use to determine the coordinates of labeling ? I have DimensionX-Y-Z and Centroid X-Y-Z from segment features but i need to have polygonal point coordinates information to capture the contour of the object.
Thanks,
Canset

[LukasS]

Hi Canset,

I’m glad it works! Getting the vertices of the polygon sounds difficult to me right now - do you maybe have an example of your labelings? How and where do you specify the vertices of the polygon - maybe there is a way of getting them right there in order to save them out? If not, I can think of the Convex Hull node, which you could apply to the bitmask of your labeling. Maybe this would help to find a non-pixel representation of the outline, e.g. via python or the like?

Best,
Lukas

[mcanset]

Hi Lukas,

I mean with using interactive annotator, i already created polygon labels. Is there a way to access point information from interactive annotator and export as .json format.

Many thanks for your time,

Canset

[LukasS]

Hi Canset,

unfortunately, it doesn’t seem possible with the Interactive Annotator to get the polygon vertices, at least I can’t think of a way.

A cumbersome approach that might work: You can try and find the polygon lines afterwards, e.g. with a Hough Transform (see e.g. this workflow). If your polygon resembles the shape of a circle, you might abstract them this way and detect circles instead?

Since this is unsatisfactory at best, however, I asked internally whether there is a more clever way of getting the polygon vertices right from the annotator. If there is a better solution I’ll come back to you in this topic and I also added a feature request (for internal reference: AP-11010)

Kind regards,
Lukas