Image processing system having variably controllable pixel density patterns

• US 5,696,853 A
• Filed: 02/26/1993
• Issued: 12/09/1997
• Est. Priority Date: 02/28/1992
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Sakakibara, Manabu, Maekawa, Shinichiro, Kosaka, Toru, Seto, Kaoru, Kawana, Takashi
• Primary Examiner(s): Couso, Jose L.
• Assistant Examiner(s): Bella, Matthew C.
• Application Number:
  US08/023,360
• Time in Patent Office: 1,747 Days
• Field of Search: 358/296, 358/298, 358/451, 358/458, 358/459, 358/461, 358/467, 358/456, 382/54, 382/299, 235/432
• US Class Current: 382/299
• CPC Class Codes: H04N 1/4055 producing a clustered dots or a size modulated halftone pattern
• CPC Class Codes: H04N 1/4056 the pattern varying in one dimension only, e.g. dash length, pulse width modulation [PWM]

Abstract

On the basis of inputted multivalued image data, direction of growth is decided from a density pattern having a plurality of growth directions and a density pattern is caused to grow based upon the growth direction that has been decided. As a result, character images are formed sharply and high-quality half-tone images exhibiting reduced density irregularity can be produced.

Claims

1. An image processing apparatus comprising:

input means for inputting image data of a pixel of interest, the image data for the pixel of interest having plural bits;

density pattern generating means for generating a predetermined density pattern corresponding to a density level of the image data inputted by said input means; and

random number generating means for generating a random number which differs from a random number generated for a previous pixel of interest;

wherein said density pattern generating means includes means for changing a growth direction of the density pattern so that the growth direction of the density pattern changes in accordance with the random number generated by said random number generating means.

2. The image processing apparatus according to claim 1, wherein said input means inputs image data of the pixel of interest and also inputs image data of its neighboring pixels, the image data for each pixel having plural bits, and wherein, in a case where the growth direction of the density pattern of the neighboring pixels in accordance with the random number is predetermined, said density pattern generating means generates the growth direction of the density pattern of the pixel of interest also to be the predetermined growth direction, regardless of the direction determined in accordance with the random number.

3. An image processing apparatus comprising:

input means for inputting image data of a pixel of interest and of its neighboring pixels, the image data for each pixel having plural bits;

discriminating means for discriminating density level of the image data inputted by said input means; and

density pattern generating means for generating a predetermined density pattern corresponding to the density level of the image data inputted by said input means;

wherein, in a case where the density level of the image data is discriminated as high by said discriminating means, said density pattern generating means generates the density pattern in a first resolution by using image data of n neighboring pixels inputted by said input means, whereas in a case where the density level of the image data is discriminated as low, said density pattern generating means generates the density pattern in a second resolution which is inferior to the first resolution by using image data of m (n<

m) neighboring pixels inputted by said input means.

4. The image processing apparatus according to claim 3, wherein the second resolution has lower resolution in a main scanning direction than the first resolution.

5. The image processing apparatus according to claim 3, wherein said density pattern generating means generates the density pattern of a pixel in the first resolution in a case where the pixel is one line below a pixel having a density pattern generated in the first resolution, regardless of the density level discriminated by said discriminating means.

6. The image processing apparatus according to claim 3, wherein said density pattern generating means generates the density pattern of a pixel in the second resolution in a case where the pixel is one line below a pixel having a density pattern generated in the second resolution, regardless of the density level discriminated by said discriminating means.

7. An image processing apparatus comprising:

input means for inputting image data of a pixel of interest and of its neighboring pixels, the image data for each pixel having plural bits;

detecting means for detecting a difference of a density level between the image data of the pixel of interest and the neighboring pixels; and

density pattern generating means for generating a predetermined density pattern corresponding to the density level of the image data inputted by said input means,

wherein, in a case where the detected difference is larger than a predetermined value, said density pattern generating means generates the density pattern in a first resolution by using image data of n neighboring pixels inputted by said input means, whereas in a case where the detected difference is smaller than a predetermined value, said density pattern generating means generates the density pattern in the second resolution which is inferior to the first resolution by using image data of m (n<

m) neighboring pixels inputted by said input means.

8. The image processing apparatus according to claim 7, wherein, if the detected difference is smaller than the predetermined value, and also if the level of the image data of the neighboring pixels surpasses a reference value, said density pattern generating means generates a density patterns of the first and second pixels in the first resolution.

9. An image processing method comprising the steps of:

inputting image data of a pixel of interest, the image data for the pixel of interest having plural bits;

generating a predetermined density pattern corresponding to a density level of the image data inputted in said inputting step; and

generating a random number which differs from a random number generated for a previous pixel of interest;

wherein said density pattern generating step includes a changing step for changing a growth direction of the density pattern so that the growth direction of the density pattern changes in accordance with the random number generated in said random number generating step.

10. The image processing method according to claim 9, wherein said inputting step inputs image data of the pixel of interest and also inputs image data of its neighboring pixels, the image data for each pixel having plural bits, and wherein, in a case where the growth direction of the density pattern of the neighboring pixels in accordance with the random number is predetermined, said density pattern generating step generates the growth direction of the density pattern of the pixel of interest also to be the predetermined growth direction, regardless of the direction determined in accordance with the random number.

11. An image processing method comprising the steps of:

inputting image data of a pixel of interest and of its neighboring pixels, the image data for each pixel having plural bits;

discriminating density level of the image data inputted in said inputting step; and

generating a predetermined density pattern corresponding to the density level of the image data inputted in said inputting step;

wherein, in a case where the density level of the image data is discriminated as high in said discriminating step, said density pattern generating step generates the density pattern in a first resolution by using image data of n neighboring pixels inputted in said inputting step, whereas in a case where the density level of the image data is discriminated as low, said density pattern generating step generates the density pattern in a second resolution which is inferior to the first resolution by using image data of m (n<

m) neighboring pixels inputted in said inputting step.

12. The image processing method according to claim 11, wherein the second resolution has lower resolution in a main scanning direction than the first resolution.

13. The image processing method according to claim 11, wherein said density pattern generating step generates the density pattern of a pixel in the first resolution in a case where the pixel is one line below a pixel having a density pattern generated in the first resolution, regardless of the density level discriminated in said discriminating step.

14. The image processing method according to claim 11, wherein said density pattern generating step generates the density pattern of a pixel in the second resolution in a case where the pixel is one line below a pixel having a density pattern generated in the second resolution, regardless of the density level discriminated in said discriminating step.

15. An image processing method comprising the steps of:

inputting image data of a pixel of interest and of its neighboring pixels, the image data for each pixel having plural bits;

detecting a difference of a density level between the image data of the pixel of interest and the neighboring pixels; and

generating a predetermined density pattern corresponding to the density level of the image data inputted in said inputting step,

wherein, in a case where the detected difference is larger than a predetermined value, said density pattern generating step generates the density pattern in a first resolution by using image data of n neighboring pixels inputted in said inputting step, whereas in a case where the detected difference is smaller than a predetermined value, said density pattern generating step generates the density pattern in the second resolution which is inferior to the first resolution by using image data of m (n<

m) neighboring pixels inputted in said inputting step.

16. The image processing method according to claim 15, wherein, if the detected difference is smaller than the predetermined value, and also if the level of the image data of the neighboring pixels surpasses a reference value, said density pattern generating step generates a density patterns of the first and second pixels in the first resolution.