Improved algorithm for scanned blueprint image preprocessing and enhancing

It is an important task for blueprint images on paper to be computerized in architecture, platting and mechanical engineering. In this paper, the intrinsic characteristics of blueprints are carefully examined, and a mathematical method is developed to measure the quality of a digitized blueprint image. Based on the method of lines and blocks primary identification and local area soft boundary brightness and contrast equalization, a new image preprocessing and enhancing algorithm is developed, which can greatly reduce the grainy noises and enhance the lines and blocks information comparing with the traditional processing method, and a high quality image can be offered to the image vectorization processing phase.