I would like to get the coordinates of framed text on an image. The paragraphs have thin black borders. The rest of the image contains usual paragraphs and sketchs.
Here is an example: 
Do you have any idea of what kind of algorithms should I use in Python with an image library to achieve this ? Thanks.
A few ideas to detect a framed text which largely comes down to searching boxes/rectangles of substantial size:
find contours with OpenCV, analyze shapes using cv2.approxPolyDP() polygon approximation algorithm (also known as Ramer–Douglas–Peucker algorithm). You could additionally check the aspect ratio of the bounding box to make sure the shape is a rectangle as well as check the page width as this seems to be a known metric in your case. PyImageSearch did this amazing article:
in a related question, there is also a suggestion to look into Hough Lines to detect a horizontal line, taking a turn a detecting vertical lines the same way. Not 100% sure how reliable this approach would be.
Once you find the box frames, the next step would be to check if there is any text inside them. Detecting text is a broader problem in general and there are many ways of doing it, here are a few examples:
apply EAST text detector
tesseract (e.g. via pytesseract) but not sure if this would not have too many false positives
if it is a simpler case of boxes being empty or not, you could check for average pixel values inside - e.g. with cv2.countNonZero(). Examples:
Additional references:
