Method and apparatus for processing image signal
First Claim
1. A method for processing image signals comprising the steps of:
- determining an averaging mask size in accordance with a pitch of a periodic pattern in image information corresponding to said image signals, respectively,smoothing said image information containing said periodic pattern to obtain a first unsharpness signal,sharpening said first unsharpness signal to obtain a second unsharpness signal and halftoning said second unsharpness signal to form a halftone image signal, wherein said smoothing step is performed with reference to said averaging mask size.
1 Assignment
0 Petitions
Accused Products
Abstract
In an improved method and apparatus for processing image signals, an input original image signal that contains a periodic pattern is smoothed to obtain a first unsharpness signal which is then processed for sharpness to obtain an output image signal having its edge enhanced and this output image signal is halftoned to obtain a halftone image signal from which a halftone image is reproduced. The mask size used in the smoothing step is computed in accordance with the pitch of said periodic pattern as optionally combined with the factor of scaling for conversion from an input to an output image. Alternatively, said first unsharpness signal is processed for sharpness only when the difference between said first unsharpness signal and the second unsharpness signal which is obtained by smoothing it is greater than a predetermined threshold value. The apparatus is capable of reproducing a sharp image with minimum moire even if the input original image contains a periodic pattern.
84 Citations
21 Claims
-
1. A method for processing image signals comprising the steps of:
-
determining an averaging mask size in accordance with a pitch of a periodic pattern in image information corresponding to said image signals, respectively, smoothing said image information containing said periodic pattern to obtain a first unsharpness signal, sharpening said first unsharpness signal to obtain a second unsharpness signal and halftoning said second unsharpness signal to form a halftone image signal, wherein said smoothing step is performed with reference to said averaging mask size. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A method for processing image signals comprising the steps of:
-
determining a mask size in accordance with a pitch of a periodic pattern in original image information corresponding to said image signals, respectively; smoothing a readout of said original image information with reference to said mask size to obtain a first unsharpness signal; smoothing said first unsharpness signal to obtain a second unsharpness signal; determining the difference between said first unsharpness signal and said second unsharpness signal; comparing said difference with a predetermined threshold value; sharpening said first unsharpness signal to obtain an output image signal only when the absolute value of said difference is greater than said threshold value; and halftoning said output image signal. - View Dependent Claims (7, 8, 9, 11, 12, 13, 14, 15, 16, 17)
-
-
10. An apparatus for processing image signals comprising:
-
a mask size computing circuit that determines a mask size in accordance with a pitch of periodic pattern in original image information corresponding to said image signals, respectively; a first smoothing circuit that smoothes a readout of said original image information with reference to said mask size to obtain a first unsharpness signal; a second smoothing circuit that smoothes said first unsharpness signal to obtain a second unsharpness signal; a differential circuit that determines the difference between said first and second unsharpness signals; a comparator circuit that compares the absolute value of said difference with a predetermined threshold value; a sharpening circuit that sharpens said first unsharpness signal to obtain an output image signal when the absolute value of said difference is greater than said threshold value; a circuit that directly delivers one of said first unsharpness signal and said second unsharpness signal as said output image signal when the absolute value of said difference is at most equal to said threshold value; and a halftoning circuit that halftones said output image signal. - View Dependent Claims (18, 19, 20, 21)
-
Specification