Image processing apparatus

• US 5,153,925 A
• Filed: 04/27/1990
• Issued: 10/06/1992
• Est. Priority Date: 04/27/1989
• Status: Expired due to Fees

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Yamada, Yasuhiro, Tanioka, Hiroshi
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Fox, David
• Application Number:
  US07/515,222
• Time in Patent Office: 893 Days
• Field of Search: 382/50, 382/52, 358/455, 358/462, 358/464, 358/466
• US Class Current: 382/272
• CPC Class Codes: H04N 1/4053 with threshold modulated relative to input image data or vice versa

Abstract

An image processing apparatus comprises: first binarizing means for binarizing input image data by an average value based on the binarized data of pixels near an objective pixel which has already been binarized; second binarizing means for binarizing the input image data by a predetermined threshold vlaue; and selecting means for selecting either one of the first and second binarizing means in accordance with whether the input image data indicates an edge portion or not, whereby by selecting either a binarizing process by the average density preservation method or a binarizing process by a fixed threshold value in accordance with the presence or absence of an edge of input data, an image of a high grade can be reproduced for either a half tone image or a character image.

Claims

1. An image processing apparatus comprising:

input means for inputting multi-level data of an object pixel which is an object o binarization processing;

calculating means for producing weighted binary data by performing predetermined weighting on binary data of plural pixels near the object pixel, the binarization processing of the plural pixels having been completed, and for calculating an average value using the weighted binary data;

first binarizing means for binarizing the multi-level data of the object pixel, using the average value calculated by said calculating means as a threshold value;

second binarizing means for binarizing the input multi-level data of the object pixel, using a predetermined threshold value;

detecting means for detecting whether or not the data of the object pixel exist in ann edge portion, on the basis of the binary data of the plural pixels on which the binarization processing has been completed; and

selecting means for selecting either one of said first and second binarizing means in accordance with a detection result of said detecting means.

2. An apparatus according to claim 1, wherein said first binarizing means has error diffusing means for diffusing binarization errors.

3. An apparatus according to claim 1, wherein said average value and a selection signal of said selecting means are stored in memory means by using the binary data of the pixels near the object pixel as addresses.