go for edge detection operators in spatial domain

i am using sobel operator how to perform runlength along gradient direction on every edge pixels

As far as I understand you want to collect

the points that make up an edge on an

image to which you have applied the

Sobel operator.

What about doing it with a custom flood fill

algorithm? Or, if you want to use a

conventional flood fill algorithm, you

could do a Gauss blur first, followed by

applying a threshold.

Regards,

Joachim