A digitized image is encoded by detecting edges in the image, encoding the position and sharpness of the detected edges, filtering the image by a low-pass filter to generate a low-frequency image, and encoding the low-frequency image. A digitized image encoded in this way is reconstructed by generating a horizontal edge image and a vertical edge image from the encoded edge position and sharpness information, synthesizing a pair of high-frequency images by filtering the horizontal and vertical edge images with an edge synthesis filter, decoding the low-frequency image, and performing an inverse wavelet transform on the decoded low-frequency image and the high-frequency images.

Image encoding and decoding method and apparatus using edge synthesis and inverse wavelet transform

A method for adaptive error diffusion. The method includes the steps of receiving input image data, detecting edges in the input image data, and then adding noise to the input image data depending upon results of said edge detection. The amount of noise is higher for pixels with higher edge content, unless the pixel is on an edge that is already sharp. Once the noise is added the method performs error diffusion on the noise-enhanced image data and it produces output image data. Alternatively, noise can be added to the thresholding portion of the error diffusion process.

Adaptive error diffusion with improved edge and sharpness perception

In the error diffusion technique for digital halftoning the output color for a first pixel is selected by comparing an adjusted input color signal to a boundary separating output colors in a pallette for a display device. The error or difference between the selected output color and the input color signal is determined and portions of that difference are added to the input color signals for neighboring pixels diffusing the error throughout the area neighboring the first pixel. Error diffusion can create artifacts in the image as rendered by the display device. Error diffusion artifacts are reduced or eliminated by a higher order error diffusion method where the boundary separating output colors in the device's pallette is adjusted as a function of the error in a previous pixel.

Higher order error diffusion of digital halftoning

There is described an image processing apparatus, which makes it possible not only to eliminate the deterioration of the perceptibility, but also to determine the pages being suitable for applying the predetermined image processing. The control section determines specific pages, being suitable for applying a predetermined image processing, based on the attributes detected by the detecting section, so as to apply the predetermined image processing to the specific pages. On the other hand, the control section applies image processing, including a variable power processing, to both the partial image area and the partial character area by employing different magnification factors, so as to generate a size-changed partial image area and a size-changed partial character area, and to arrange both of them into a predetermined imaginary area being smaller than an area of the original image, so as to accommodate them within the predetermined imaginary area.

Image-processing apparatus

An image processing apparatus can obtain a copy image having excellent reproducibility with a relatively simple structure of a processing unit that processes image data. The image processing apparatus generates image formation data by processing image data. A gradation processing unit binarizes the image data according to an error diffusion process so as to convert the image data into binary image data. A character/line drawing detection unit determines whether a part of the binary image data corresponds to a character/line drawing portion that consists of characters or line drawings so as to detect the character/line drawing portion. An image processing unit applies an image processing to the part of the binary image data by using an image processing method according to a result of determination of the character/line drawing detection unit.

Image processing apparatus, an image forming apparatus and an image processing method

An image processing system for displaying pixel data on a screen performs a binary-encoding method using error diffusion with edge enhancement. In the method for binary-encoding the image data, pixels to be binary-encoded are divided into normal and edge regions, and the pixel data is binary-encoded in accordance with the divided regions. By using the method, bars on the display screen which are unpleasant to the eye can be removed and an image with good edge sharpness can be obtained.

Method and apparatus for binary-encoding image data using error diffusion with edge enhancement

Disclosed is a image processing system for displaying pixel data on a screen. In the method for binary-encoding the image information, a currently processed pixel is discriminated according to whether it is involved in normal or edge regions of the image, and the binary-encoding of the pixel information is performed in accordance with the discrimination, as is the determination of a corresponding error value. According to the method, unpleasant bars to the eye can be removed on a screen and therefore an image quality with good edge sharpness can be obtained.

Tae-Il Chung

Papers

Method and apparatus for binary-encoding image data using error diffusion with edge enhancement

Error diffusion image encoding