JP2000196859A - Image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the quality degradation of contone images, even in the case that bitone images and the contone images coexist by dividing images into plural small areas, encoding the image information of the divided small areas, storing it in a bit group and sweeping out the bit group from a memory to a display output part after encoding it. SOLUTION: A bitone image 1 and a contone image 2 are separated from the information of a page description language sent from a host computer. In the bitone image 1 of characters and linear graphics, etc., since it is not required to express tones, information is converted into information of 1 bit per pixel. In the contone image 2 of the image of photographs and pictures, etc., since the tones are expressed, it is converted into the information of K bits per pixel. In order to distinguish the two kinds of the images, one page is divided into the rectangular areas of vertical M pixels and horizontal N pixels size and attribute bits are supplied in one-to-one correspondence with the pixels inside the rectangular area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method in an image forming apparatus such as a printer which is required to reproduce an image as an original on a small-capacity storage medium at high speed and with high fidelity.

[0002]

2. Description of the Related Art In an image forming apparatus such as a printer, information sent from a host computer is handled in units of pixels, and N (N = 1, 2, 3,...)
Bit information is stored and stored in a storage medium such as a RAM. After that, some processing is performed on the stored information as it is or in order to improve the quality of the image, and the stored information is discharged to the display output unit. It is known that a horizontal or vertical line becomes jaggy with respect to a Viton image such as a character or a line in an image, and a process for improving the line is performed.

On the other hand, for a contone image such as a photograph or a painting in an image, pseudo intermediate image processing is performed in order to reproduce the halftone beautifully.

[0004]

However, in the above-mentioned prior art, when a Viton image such as a character or a line in an image and a Contone image such as a photographer's painting are mixed, the processing for the Viton image is performed by the Contone image. Adverse effects such as being performed for As a result of this adverse effect, the quality of the contone image is degraded.

An object of the present invention is to solve the above-mentioned problems and to provide an image processing method for preventing the quality of a contone image from deteriorating even when a vitone image and a contone image are mixed.

[0006]

In order to solve the above problems, the present invention divides an image into a plurality of small areas, encodes image information of the divided small areas, and stores the image information in a memory corresponding to the small areas. The bit group is stored, and the bit group is decoded and swept out when the bit group is swept from the memory to the display output unit.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram of a Viton image and a contone image. FIG. 2 is a diagram showing division into a plurality of M × N rectangular areas. FIG. 3 is a data plane and attribute plane storage state of a VRAM. FIG. 4 is a diagram showing a data plane of a region adjacent to the region of interest, and FIG.
FIG. 8 is a diagram illustrating an attribute plane of an area adjacent to the attention area.

First, according to the present invention, as shown in FIG. 1, a Viton image 1 and a Contone image 2 are separated from the page description language information sent from the host computer. In the case of a Viton image 1 such as a character or a line figure, since it is not necessary to represent a tone, it is converted into information of one bit per pixel. In the contone image 2 of an image such as a photograph or a picture, the information is converted into K (K = 1, 2, 3, 4,...) Bits of information per pixel in order to express a tone.

In the present embodiment, in order to distinguish these two types of images, one page is divided into a rectangular area 3 having a size of M pixels vertically and N pixels horizontally, and one pixel in the rectangular area 3 is divided into one page.
Attribute bit 4 is given corresponding to pair 1. This attribute bit 4 has an attribute of whether it is a contone image or a Viton image. As shown in FIG. 3, when the pixel data is arranged in the raster order in consideration of the printing order, as shown in FIG.
The pixel data is stored at a position in the VRAM corresponding to each pixel data of the rectangular area 3 of N pixels in the main scanning direction.

When the entire area of the rectangular area 3 is a contone image, the halftone having two M × N power gradations is expressed by using the information of M × N bits in the rectangular area 3. , The VRA at the position corresponding to the rectangular area 3
M × N bits of information are encoded in the M area and stored in the VRAM. In this case, all attribute bits in the rectangular area 3 become 1 (5).

On the other hand, all of the rectangular area 3 is Viton
In the case of an image, the square area 3 is set to 1 per pixel.
The information is binarized into bit information and stored in a VRAM area at a position corresponding to the rectangular area 3 as a bit map. In this case, all the attribute bits in the rectangular area 3 become 0 (6).

Further, when the Viton image and the Contone image are mixed in the rectangular area 3, the Viton image portion (the attribute bit is 0) is binarized into 1-bit information per pixel, and The image portion (the attribute bit is 1) is interpolated by the information of the adjacent rectangular area 3 to form a bit map. That is, after this processing, the mixed rectangular area 3 is treated as a Viton image.

Next, an embodiment using a 3 × 3 square area as the square area 3 will be described. In this embodiment, since one pixel is divided into a 3 × 3 square area, when all the attribute bits in the area are 1 (when the area is all contone images), 5 3x3 as
= 9 bits are used to represent 512 (2 9) grayscale data.

Next, an example of a method of interpolating to make a bitmap when a Viton image and a contone image are mixed in the rectangular area 3 will be described with reference to FIG. First, a 3 × 3 area 7 where a Viton image and a contone image arbitrarily located on a pixel are mixed.
Pay attention to. The average gray value of the 3 × 3 regions 8, 9, and 10 in which the attributes of all pixels in the region adjacent to the region of interest 7 are contones is obtained. Next, within the 3 × 3 area 7 of interest by Equation 1, the number L of pixels whose data should be 1 when converted into a bitmap is determined.

[0016]

(Equation 1)

In this embodiment, when Equation 1 is applied, Equation 2 results.

[0018]

(Equation 2)

From equation (2), the number L of pixels for which the data should be 1
Is calculated, the number of pixels whose data is 1 is counted in the byteon image portion of the attention area 7, and if the number is equal to or larger than the number L of pixels where the data should be 1, the contone image of the attention area 7 is obtained. Part of the data is interpolated as 0. If the number is smaller than the number L of pixels for which the data should be 1, the data of the contone image portion of the region of interest 7 is in raster order until the number of pixels of 1 in the region of interest 7 becomes L pixels. The data is interpolated as 1. When the number of pixels having data of 1 becomes L in the attention area 7, the data of the remaining contone image portion is interpolated by 0.

Referring to FIG. 5, another interpolation method will be described.
First, attention is paid to a 3 × 3 region 11 in which a vitone image and a contone image are arbitrarily located on the image. The average density value of the 3 × 3 area (12, 13, 14) in which the attributes of all pixels in the area adjacent to the area of interest 11 are contones is obtained. Next, the logical sum of the logical product of the halftone screen corresponding to the average gray value and the attribute plane of the attention area 11 and the data plane of the attention area 11 is obtained. This result is used as a new data plane of the attention area 11.

In this way, the information stored in the VRAM is swept out to the laser scanner unit. In the process, in a rectangular area whose attribute is contone, the systematic dither method, the error diffusion method, etc. Is expressed in a contone on an image forming apparatus such as a monochrome printer. In a rectangular area whose attribute is Viton, the edge in the bitmap image is smoothed by the high-density and high-resolution image forming method, and is beautifully reproduced on the image forming apparatus.

[0022]

As described above, according to the present invention, an image is divided into a plurality of small areas, and attributes are assigned to each area, so that a vitone area and a contone area can be processed independently. Therefore, the image display speed is not reduced. Further, deterioration of the contone image can be prevented.

[Brief description of the drawings]

FIG. 1 shows a Viton image and a Contone image.
FIG.

FIG. 2 is a diagram illustrating division into a plurality of M × N rectangular regions;

FIG. 3 is a diagram illustrating a storage state of a data plane and an attribute plane of a VRAM;

FIG. 4 is a diagram showing a data plane in an area adjacent to a target area 7;

FIG. 5 is a diagram showing an attribute plane of an area adjacent to the area of interest 11;

[Explanation of symbols]

Reference Signs List 1 bitone image 2 contone image 3 M × N square area 4 attribute bit 5 area where attribute of all pixels in area is contone 6 area where attribute of all pixels in area is viton 7 data plane of attention area 8 , 9, 10 all-pixel contone image, data plane of the area adjacent to the area of interest 11 attribute plane of the area of interest 12, 13, 14 all-pixel contone image, attribute plane of the area adjacent to the area of interest

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) BB05

Claims (2)

[Claims] An image is divided into a plurality of small areas, image information of the divided small areas is encoded and stored in a bit group in a memory corresponding to the small area, and the bit group is transferred from the memory to a display output unit. An image processing method characterized in that it is configured to decode and sweep out when sweeping out. 2. When storing data and attributes of image information in the memory, the memory is divided into an upper area and a lower area.
2. The image processing system according to claim 1, wherein data is stored in one area and an attribute is stored in another area in consideration of the order of sweeping from the memory to the display output unit.