Frishauf, Holtz, Goodman & Woodward
Image processing apparatus capable of processing halftone image data
 When image data having a halftone is binary-coded, each of pixel data is first read out as gradation data having multiple values, a judgement is made whether or this pixel data corresponds to a value within a predetermined range, and if this pixel data is present within this range, a halftone processing operation is carried out by way of the error diffusion method. On the other hand, if another judgement is made that the pixel data is out of this predetermined range, this pixel is simply binary-coded. Thus, a portion where characters have been written is not processed by the halftone processing operation by way of the error diffusion method, whereby a clear image may be reproduced. 
Casio Computer Co., Ltd.
H
H04N
inventional
Nobuaki Yasunobu Takahisa
Kuwabara Suzuki Endou