Methods and systems for detecting stamps in scanned documents

A system for detecting stamps in documents, the system comprising:

• at least one computer processor;
• and
• a memory containing instructions which, when executed by the at least one processor, cause the at least one processor to perform a sequential algorithmic method, the sequential algorithmic method comprising the steps of:
• if at least one regular shape in an image of a document is detected then outputting said at least one regular shape as a stamp;
• else:
• removing at least one of text, lines, and noise in the image of the document;
• and
• if at least one closed shape is remaining in the image of the document, then inscribing said at least one closed shape and outputting said at least one inscribed closed shape as a stamp;
• else
• if at least one open shape is remaining in the image of the document, then enclosing said at least one open shape and outputting said at least one enclosed shape as a stamp, wherein the at least one processor is configured to enclose at least one remaining open shape in the image of the document by:
• identifying large objects in the image relative to a font size;
• detecting edges in the image of the document;
• calculating one or more contours in the image of the document;
• filtering the one or more contours to identify at least one contour with points approximating a shape selected from a predefined list of regular shapes;
• enclosing the at least one contour with the selected shape;
• determining if the at least one contour is the same shape as the selected shape;
• applying a mask of the selected shape to the image of the document and outputting the result as a stamp.

A sequential computerized algorithmic method for detecting stamps in documents, the method comprising, using a computer processor:

• if at least one regular shape in an image of a document is detected then outputting said at least one regular shape as a stamp;
• else:
• removing at least one of text, lines, and noise in the image of the document;
• and
• if at least one closed shape is remaining in the image of the document, then inscribing said at least one closed shape and outputting said at least one inscribed closed shape as a stamp, wherein inscribing at least one remaining closed shape in the image of the document comprises:
• identifying large objects in the image relative to a font size;
• detecting edges in the image of the document;
• calculating at least one contour in the image of the document;
• obtaining a convex hull of the at least one contour;
• determining a shape of the convex hull by iteratively inscribing a maximum shape selected from a predefined list of regular shapes inside the convex hull;
• and
• applying a mask of the determined shape to the image of the document and outputting the result as a stamp;
• else
• if at least one open shape is remaining in the image of the document, then enclosing said at least one open shape and outputting said at least one enclosed shape as a stamp.

A sequential computerized algorithmic method for detecting stamps in documents, the method comprising, using a computer processor:

• if at least one regular shape in an image of a document is detected then outputting said at least one regular shape as a stamp;
• else:
• removing at least one of text, lines, and noise in the image of the document;
• and
• if at least one closed shape is remaining in the image of the document, then inscribing said at least one closed shape and outputting said at least one inscribed closed shape as a stamp;
• else
• if at least one open shape is remaining in the image of the document, then enclosing said at least one open shape and outputting said at least one enclosed shape as a stamp;
• and
• detecting at least one colored stamp in the image of the document, said detecting comprising:
• converting the image of the document to an HSV color space;
• selecting a first predefined H value interval;
• for the selected H value interval:
• calculating an S component which minimizes a quantity of white pixel blobs in the converted image of the document;
• binarizing a resulting image having said S component;
• inverting the binarized image;
• applying an OR mask to the image of the document using the inverted image;
• and
• detecting at least one regular shape in the masked image of the document and outputting said at least one regular shape as a colored stamp;
• and
• iteratively repeating for a different H value interval if no colored stamp is output.