Image processing system

• US 5,539,843 A
• Filed: 02/07/1992
• Issued: 07/23/1996
• Est. Priority Date: 11/20/1987
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Masuzaki, Hidefumi, Kurosu, Yasuo, Murakami, Tatsuya, Fujisawa, Hiromichi, Fujinawa, Masaaki
• Primary Examiner(s): Couso, Jose L.
• Assistant Examiner(s): Bella, Matthew C.
• Application Number:
  US07/832,700
• Time in Patent Office: 1,628 Days
• Field of Search: 382/50, 382/47, 382/9, 382/173, 382/270, 382/304, 382/237, 358/433, 358/456, 358/457
• US Class Current: 382/270
• CPC Class Codes: G06T 3/40 Scaling of whole images or parts thereof, e.g. expanding or contracting
• CPC Class Codes: G06T 3/4023 based on decimating pixels or lines of pixels; based on inserting pixels or lines of pixels
• CPC Class Codes: H04N 1/40062 Discrimination between different image types, e.g. two-tone, continuous tone
• CPC Class Codes: H04N 1/40075 Descreening, i.e. converting a halftone signal into a corresponding continuous-tone signal; Rescreening, i.e. combined descreening and halftoning
• CPC Class Codes: H04N 1/4053 with threshold modulated relative to input image data or vice versa

Abstract

An image processing system wherein for an inputted composite image composed of a line image and a dither image, both a line image processing and a dither image processing are carried out in parallel, and one of the processed results as selected in accordance with the image region discrimination result. The dither image processing is carried out through data conversion for calculating multivalued gray scale image from the inputted image data, gray scale data conversion for adjusting the gray scale image data so as to match an output device and obtaining such adjusted gray scale image data, and re-binarization for re-binarizing the gray scale image data after subjected to the gray scale conversion. The image region discrimination for discriminating if an image region is of a line image of a dither image is carried out based on a ratio of the number of black or white pixels within the region to the contour line length within the range. In ordered dither image through a screened type dither matrix is discriminated in accordance with a correlation between adjacent pixel trains each having a predetermined number of pixels.

Claims

1. An image processing system for processing a digital binary image, comprising:

image memory means for temporarily storing first binary image data;

determining means for determining, on the basis of the first binary image data stored in said image memory means, one of a line image area and a pseudo gray scale image area to which a point to be processed of the image belongs;

means for scanning, when it is determined by said determining means that said point to be processed belongs to the pseudo gray scale image area, said first binary image data in said image memory means with a first scan window of m1×

n1 pixel where is m1×

n1 is greater than 1, on an arbitrary coordinate system;

means for converting said first binary image data of m1×

n1 pixels scanned with said first scan window into multivalued gray scale image data;

means for scanning, when it is determined by said determining means that said point to be processed belongs to the line image area, said first binary image data in said image memory means with a second scan window of m2×

n2 pixel where m2×

n2 is greater than 1, on a arbitrary coordinate system; and

means for converting said first binary image data of m2×

n2 pixels scanned with said second scan window into second binary image data.

2. An image processing system according to claim 1, further comprising means for controlling independently the operation timing of said means for scanning said original image data P in said image memory means with a scan window of m₁ ×

n₁ pixels where m₁ ×

n₂ is greater than 1 and n₁ is 1 or larger, using an arbitrary coordinate system, and the operation timing of said means for determining multivalued gray scale image data Sp based on the binary image data of m₁ ×

n₁ within said scan window.

3. An image processing system according to claim 2, wherein

said means for independently controlling the operation timing of said scan window and the operation timing of outputting said multivalued gray scale image data Sp comprises means for detecting small value portions Δ

x and Δ

y of relative positions of said scan window to pixels within said scan window at the time of outputting said multivalued gray scale image data Sp; and

said means for determining said multivalued gray scale image data Sp comprises means for multiplying binary data of respective pixels within said scan window by associated weight coefficients corresponding to said outputs Δ

x and Δ

y from said detection means, and means for adding together said multiplied results.

4. An image processing apparatus for processing a digital, binary image comprising:

image memory means for temporarily storing binary image data P of an original image;

means for scanning said binary image data P in said image memory means with a scan window of M1 pixels (M₁ >

1);

means for determining multivalued data S based on said binary image data of M1 pixels within said scan window; and

means for binarizing said multivalued data S;

wherein said means for binarizing said multivalued data S comprises;

means for adding an error adjustment quantity E to said multivalued data S to obtain multivalued data F, and

means for comparing said multivalued data F with a predetermined value C and outputting binary data Q which are given by;

space="preserve" listing-type="equation">if F>

C, then Q=1

space="preserve" listing-type="equation">if F<

C, then Q=0

and wherein said error adjustment quantity E is the sum of values of, rounding errors ε

generated during binarization of neighboring pixels within a predetermined region, multiplied by predetermined coefficients.

5. An image processing apparatus according to claim 4, wherein

said means for determining said binary data Q from said multivalued data S comprises:

first and second image memory means for storing said multivalued data S;

means for scanning said first memory means with a first scan window of M₂ pixels and obtaining the sum Sm of said multivalued data S within said scan window;

means for obtaining a sum F of said Sm and said error adjustment quantity E;

means for calculating an integer N by an equation F=C×

N+n using a predetermined value C and said sum F;

means for scanning said second image memory means with a second scan window in synchro with scanning of said first image memory means with said first scan window;

means for adding a predetermined adjustment value to respective multivalued data of M₂ pixels within said scan window and assigning a number to each of the resultant multivalued data in ascending number or descending number order;

means for replacing, in accordance with said number, the resultant multivalued data of N pixels in said first image memory means within said first scan window by said C, the resultant multivalued data of (N+1)-th number pixel by said n, and the remaining resultant multivalued data by 0; and

means for repeating the above operation to perform said replacement process M₂ times for each pixel, and determining said binary data Q and an error adjustment quantity E₂ which is to be added at the following pixel binarization process, by using multivalued data Sx in said first image storage means corresponding to pixels subjected to M₂ time replacements, said binary data Q and said quantity E₂ being given by;

space="preserve" listing-type="equation">if Sx≧

V, then Q=1 and E.sub.1 =C-Sx

space="preserve" listing-type="equation">if Sx<

V, then Q=0 and E.sub.1 =Sx

where V is a predetermined value.