JPH01109963A - Picture signal processing unit - Google Patents

Abstract

PURPOSE:To improve the picture quality by magnifying again a binarized picture with respect to a picture signal reducing a multi-value picture signal by arithmetic means so as to bring the area of white and black picture element into one picture element or over thereby improving the gradation characteristic. CONSTITUTION:An input picture signal is reduced by arithmetic means at a main scanning signal 1/2 reduction circuit 2 and converted into a binary signal by a random dither binarizing circuit 3. Then the main scanning signal is magnified by repeating two picture elements at a main scanning signal double magnification circuit 4 and decoded into the original size. Thus, the minimum black/ white picture element is selected to be one picture element or over and consecutive gradation characteristic is obtained even when the signal is recorded by a conventional laser printer. Since only the main scanning picture element is subject to reproduction/magnification and recovery, the deterioration in the resolution of the picture is less. Thus, the gradation characteristic is improved and the picture quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image signal processing device that displays a gradation image in binary format.

2. Description of the Related Art In recent years, with the mechanization of office processing and the rapid spread of image communication, there has been an increasing demand for high-quality image reproduction of gradation images and printed images in addition to conventional black-and-white binary originals. In particular, pseudo-halftone reproduction using a binary image of a gradation image has good compatibility with display devices and recording devices, and many proposals have been made. Among them, the Cavix method (Reference: 'New binary regeneration method (CA)
PIX) circuit configuration method 1985 IEICE Information and Systems Division National Conference 1-225) and error diffusion method [
R Froib & L Stimberbuan Adaptive Algorithm for Special Gray Scale "Nisiday 75 Digest 3
Pages 6-37 (Reference: R5FLOYD & L, ST
gINBgRG, “An AdaptiveAlgo
rithm for 5patial Gray 5c
ale”, 5ID75 DIGlflST, pp36
-37)) is known and is excellent in gradation reproducibility, image resolution, and moiré suppression.

Problems to be Solved by the Invention However, because the binary image output processed using the random dither method has many patterns in which black pixels and white pixels occur alternately and isolated points of pixels, it is difficult to correctly record each pixel as one dot. In general, binary recording can express gradations in % because the area ratio of white or black changes in proportion to the input image signal, so both white and black pixels can be accurately expressed by one pixel. If a normal laser beam printer or the like is used as an image recording device, an isolated black pixel surrounded by white pixels will not be recorded.
In addition, an isolated white pixel surrounded by black pixels tends to collapse because the black pixel area becomes larger than the regular pixel area, and smooth gradation characteristics cannot be obtained.

The present invention solves the above-mentioned problems by adopting a random dither method which has excellent characteristics, and uses image signal processing to eliminate isolated pixels and patterns of alternating black and white pixels without deterioration of image resolution. It provides equipment.

Means for Solving the Problems The present invention achieves the above object by reducing an input image signal, binarizing it using a random dither method, and then enlarging it to the original image size.

According to the above-mentioned configuration, the present invention expands again the binarized image for the image signal obtained by reducing the multilevel image signal by averaging, thereby increasing the white pixel or black pixel area to one or more pixels, thereby increasing the gradation. It improves the characteristics.

The embodiment diagram is a block diagram of an image signal processing device according to an embodiment of the present invention. Note that although the embodiment in the figure is described using one-dimensional processing, it is easy to extend it to two-dimensional processing.

1 is an input terminal for an input image signal (multilevel signal), and 2 is a main scanning signal 1/2 reduction circuit, which adds and averages the input image signal of input terminal 1 every two pixels and outputs the result. Therefore, the number of main scanning pixels is half the number of input pixels. Reference numeral 3 denotes a random dither type binarization circuit which binarizes the output signal of the main scanning signal 1/2 reduction circuit 2 using an error diffusion method or the like and outputs the binarized signal. Reference numeral 4 denotes a circuit for enlarging the main scanning signal twice, which repeats the output signal of the random dither binarization circuit 3 for two pixels and outputs it.

Therefore, the number of main scanning pixels is doubled and becomes the same number as the number of input pixels.

The operation of the above configuration will be explained below.

The input image signal at the input terminal 10 is averaged by two pixels in the main scanning signal 1/2 reduction circuit to become a main scanning 1/2 reduction signal, and then converted into a binary signal in the random dither binarization circuit 3.
By repeating the main scanning signal for two pixels in the main scanning signal double enlargement circuit 4, the image is enlarged twice and restored to the original size. Note that descriptions of the individual blocks in FIG. 1 will be omitted since they are generally well-known techniques.

According to the above embodiment, the smallest black/white pixel is 1
It can be made up of pixels or more, and continuous gradation characteristics can be obtained even when recording with a recording device such as a general laser beam printer. Furthermore, since only the main scanning pixels are reduced and enlarged for reproduction, the resolution of the image does not need to be radicalized.

Although this embodiment shows an example of reduction, binarization, and expansion of the main scanning pixel number, similar effects can be obtained with the sub-scanning pixel signal.

Effects of the Invention As described above, the present invention has great effects, such as applying the random dither method, which has excellent characteristics, to an ordinary image recording apparatus such as a laser beam printer to improve image quality.

[Brief explanation of the drawing]

The figure is a block diagram of an image signal processing device according to an embodiment of the present invention. 2... Main scanning signal 1/2 reduction circuit, 3... Random dither binarization circuit, 4... Main scanning signal 2x enlargement circuit.

Claims (1)

[Claims] an image signal reduction means for converting multivalued input image signal data into image signal data reduced by averaging and outputting it; a binarization means for converting the reduced image signal data into binarization using a random dither method and outputting the resultant image signal data; An image signal processing device comprising an image signal enlarging means for converting binarized binary pixel data into binary pixel data enlarged to the original size and outputting the converted binary pixel data.