METHOD AND DEVICE FOR THRESHOLDING PROCESSING

• Main Author: KAWASHIMA SUMIHIKO
• Format: Patent
• Language: English
• Published: 31.01.1995
• Edition: 6
• Subjects: CALCULATING; COMPUTING; COUNTING; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; IMAGE DATA PROCESSING OR GENERATION, IN GENERAL; PHYSICS; PICTORIAL COMMUNICATION, e.g. TELEVISION

PURPOSE:To perform thresholding while avoiding noise in an image and the density nonuniformity of the background by calculating a threshold value and defining it as a threshold value until a new threshold value is decided when difference between the density of an attention picture element and the density of over two picture elements separated from the attention picture element for more than one picture element is larger than a fixed value. CONSTITUTION:The density of an image signal from an image pickup device for each picture element is stored in a storage circuit 1 and sent to an edge detection circuit 2. The circuit 2 calculates the difference of density between the attention picture element and over two picture elements separated from the attention picture element for more than one picture element. The absolute value of this difference is compared with a prescribed value by an edge detection circuit 3 and when that value is larger, the edge of an image is decided. Further, it is decided by extracting over two picture elements whether the edge is sharp or smooth. Then, the threshold value of data decided as the edge is calculated by a threshold value arithmetic circuit 4, and a binary image is provided by a thresholding processing circuit 5 with this value as the threshold value until the new threshold value is calculated. Thus, even any image containing noise or the density nonuniformity of the back-ground inside can be clearly made in binary images, and image analysis is facilitated as well.