pythonopencvbounding-boximage-stitchingmser

Merging regions in MSER for identifying text lines in OCR

I am using MSER to identify text regions in MSER. I am using the following code to extract the regions and save them as an image. Currently, each identified region is saved as a separate image. But, I want to merge regions belonging to a line of text merged as a single image.

import cv2

img = cv2.imread('newF.png')
mser = cv2.MSER_create()


img = cv2.resize(img, (img.shape[1]*2, img.shape[0]*2))

gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
vis = img.copy()

regions = mser.detectRegions(gray)
hulls = [cv2.convexHull(p.reshape(-1, 1, 2)) for p in regions[0]]
cv2.polylines(vis, hulls, 1, (0,255,0))

How can I stitch the images that belong to a single line together? I get the logic to do will mostly be based on some heuristic for identifying areas with nearby y-coordinates.

But how exactly the regions can be merged in OpenCV. I am missing out on this as I am new to openCV. Any help would be appreciated.

Attaching a sample image enter image description here

The desired output(s) is as follows enter image description here

Another line enter image description here

Another Line enter image description here

Solution

  • Maybe even something as primitive as dilate-erode could be made work in your case? For example, if I use erode operation followed by dilate operation on your original image, and mostly in horizontal direction, e. g.:

    img = cv2.erode(img, np.ones((1, 20)))
img = cv2.dilate(img, np.ones((1, 22)))

    the result is something like:

    enter image description here

    So if we draw that over the original image, it becomes:

    enter image description here

    I didn't resize the original image as you do (probably to detect those small separate dots and stuff). Not ideal (I don't know how MSER works), but with enough tweaking maybe you could even use simple detection of connected components with this?