Patent ID: 9628635
Date: 2017-04-18
CPC Classifications: H04N

Claim:
1. A system for halftone frequency detection in a halftone image, the system comprising: an image source configured to capture a halftone image of a predetermined resolution, wherein the halftone image includes a plurality of pixels; a memory unit configured to store a predefined first window and a predefined second window, each including a plurality of check cells and at least one processing cell; and a threshold-based halftone frequency (THF) detector configured to: receive the first window, the second window, and the halftone image; determine measurement values of a plurality of predetermined statistical parameters for the plurality of pixels; assign an active value to a max variable or a min variable associated with a pixel from the plurality of pixels within a first pixel neighborhood defined by the first window based on an intensity value of the pixel being compared with a three-way threshold set including a maximum value, a minimum value, and a median value from a range of possible intensity values for the pixel, wherein the three-way threshold set is determined based on the values of the plurality of predetermined statistical parameters; estimate a first frequency estimate value based on a number of pixels having active values in the max variable within a second pixel neighborhood defined by the second window; estimate a second frequency estimate value based on a number of pixels having active values in the min variable within the second pixel neighborhood; and determine the halftone frequency based on the first frequency estimate value, the second frequency estimate value, and the predetermined resolution.