Image treatment method and apparatus with error dispersion and controllable quantization

• US 5,325,448 A
• Filed: 04/28/1992
• Issued: 06/28/1994
• Est. Priority Date: 11/16/1987
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Katayama, Akihiro, Ohsawa, Hidefumi, Fukuhara, Akiko
• Primary Examiner(s): Mancuso, Joseph
• Application Number:
  US07/875,210
• Time in Patent Office: 791 Days
• Field of Search: 382/50, 382/54, 382/56, 382/51-53, 358/261.2, 358/465, 358/466, 358/456, 358/459, 358/445, 358/443, 358/448, 358/430, 341/51, 341/94
• US Class Current: 382/270
• CPC Class Codes: H04N 1/4053 with threshold modulated relative to input image data or vice versa

Abstract

An image treatment apparatus comprising: an input device for inputting image data; a setting circuit serving as a reference when the image data is quantized in accordance with the image data input by the input device; a quantizing circuit for quantizing the image data; and a device for outputting an image in accordance with the result of treatment performed by the quantizing circuit, wherein the quantizing circuit performs the quantization by correcting the error between the image data input by the input device and the image output by the outputting device.

Claims

1. An image processing apparatus comprising:

input means for inputting image data;

setting means for setting a reference value to serve as a reference for use in quantizing the image data, said setting means setting the reference value based on the image data input by said input means;

quantizing means for quantizing the image data;

means for outputting an image in accordance with the result of the processing performed by said quantizing means;

judgment means for judging whether or not a dot is present in a region consisting of quantized data of plural pixels which has been quantized by said quantizing means; and

error determining means for determining an error between input image data, input prior to an object pixel input by said input means, and output image data,

wherein said quantizing means performs the quantizing in accordance with;

the image data of an object pixel input by said input means;

the error between input image data, input prior to the object pixel, and the output image data; and

the judgment by said judgment means,

wherein said setting means is so structured and arranged as to set the reference value to be smaller when the value of the image data input by said input means is small than when the value of the image data is large, and

wherein said setting means is structured and arranged as to generate plural random numbers in a predetermined region in accordance with the image data and to set one of those numbers as the reference value.