一种逐步简化的扫描工程图纸矢量化方法

Thinning-based methods
CT-based methods
RLE-based methods
SPT-based methods
P0 P1 P2 P3 P4
P3
P2 P1 P0
Existing difficulties
• Lines with intersections broken into pieces. • Texts touch lines misrecognition. • The interference of recognized objects
– IAPR TC-10, IEEE – IEEE T.PAMI, PR, PRL, CVIU, CVGIP, etc. – ICPR, ICDAR, IEEE CVPR, etc.
State of arts
• K. Tombre (LNCS vol.1389, 1998) :
“None of these methods works. … Actually, the methods do work, but none of them is perfect.”
• Save the storage space.
History
• Begin research on vectorization at late 70’s; • Begin that for engineering drawings at late
80’s; • Related organizations & publications
Phase 2: Vector-based graphical object recognition
Graphical objects: Straight lines, circle/arc, curve
Fra Baidu bibliotek
Motivation of 2PV
• Internal memory (RAM)
– Used to be high price & limit capacity – High pixel access frequency cause swap
repetitive detection, false detection.
Our research
• Analysis the vectorization model of existing methods.
• Propose an efficient vectorization model for engineering drawings.
images
(CAD files)
Why do vectorization?
• A lot of old drawings to be reused, and CAD files are more editable than images.
• Preprocess of automatic drawing understanding systems (information statistic, 3D reconstruction).
• Pixel tracking algorithm
– No guide direction – Repetitive tracking
Object-Oriented Progressive-Simplification based Vectorization Model
• 1 phase model
– Imitate the way that humans read drawings
• Recognize a graphical object in its entirety
– Object-oriented feature
• Simplify the image data as the recognition goes on
• 《CADALYST》performs the annual evaluation on commercial vectorization systems.
Review of existing methods
• Thinning based • CT(Contour Tracking) based • RLE(Run Length Encoding) based • SPT(Sparse Pixel Tracking) based
• Propose a group of new graphical object recognition algorithms.
Common model of existing methods
（2PV - 2 Phase Vectorization）
Raster image
Phase 1: Skeletonization or medial-axis approach Low level vector form: Short line segments
– Progressive-simplification feature
Workflow of OOPSV
Line
Arc
Curve
Symbol Text
Symbol Curve
Symbol Text
Text
Symbol Text
Text
S-Line
Arc
Curve
Symbol
Text
Recognition Recognition Recognition Recognition Recognition
S-Line
Arc
Curve
Symbol
Text
Graphical object recognition
• Get the intrinsic characteristic of individual type of graphical object.
Concept
• Vectorization: the conversion from a raster image to its vector-form file.
Engineering drawings Scan in paper form
Raster Vectorization Vector-form