JPH03289868A - Picture processing unit - Google Patents

Abstract

PURPOSE:To obtain a picture with high picture quality by thinning the picture in the unit of blocks comprising picture elements of a number equal to a gradation number of a pseudo half tone picture so as to reduce the picture thereby avoiding reduction in the gradation number attended with the reduction processing and occurrence of moire. CONSTITUTION:An area segmentation section 14 segments areas A1, A2, A3, A4 including four blocks each comprising 2X2 picture elements (in total 16 in picture element number) from a pseudo half tone picture memory 11. A block segmentation section 15 select a block B11 (B12, B13, B14) at an upper left corner from the area A1 (A2, A3, A4) respectively segmented by the area segmentation section 14. The data of the selected block is stored in a reduced pseudo half tone picture memory 13. Thus, no gradation number is decreased from the data from the reduced pseudo half tone picture memory 13 and the pseudo intermediate tone picture subject to reduction processing without occurrence of moire is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image processing apparatus used in personal computers, workstations, facsimile machines, and the like.

Prior art Examples of conventional image processing apparatuses that perform reduction processing on an original image that has been subjected to pseudo-halftone processing to obtain a reduced image include the one shown in Japanese Patent Application Laid-open No. 142669/1983 or the one shown in FIG. There are some things shown below.

The image processing apparatus shown in FIG. 4 includes a pseudo-halftone original image memory 1 subjected to pseudo-halftone processing by dither processing,
When the reduction ratio is (q/p) It has a pixel cutting unit 3 that selects and cuts out q×q pixels from a block that has been extracted, and a reduced image memory 4 that stores the output of the pixel cutting unit 3. Unit reduction processing was being performed.

In such an image processing apparatus, for example, the fifth
Assuming that the dithered image shown in the figure is stored in the pseudo-halftone original image memory 1, it is divided into 1/4, that is, (1
/2)x (1/2), the block cutting unit 2 sequentially cuts out blocks each consisting of four pixels from the pseudo halftone original image memory 1. Next, the pixel cutting unit 3 selects one pixel at a predetermined position (for example, the upper left corner) from among the four pixels in the block, and outputs this pixel to the reduced image memory 4. Pixels selected from each block are sequentially input to the reduced image memory 4, and a reduced pseudo halftone image 5 as shown in FIG. 6 is obtained.

Problems to be Solved by the Invention However, in such conventional image processing devices, it is difficult to process images from a pseudo-halftone original image in which shading is expressed by the overlap between the number of white dots and the number of black dots in a plurality of adjacent pixels. Since a predetermined pixel is simply extracted from a block composed of a predetermined number of pixels according to the reduction ratio, the local number of white dots and number of black dots changes.

Therefore, depending on the cutting method, the number of gradations before reduction may be reduced by the reduction process, and as seen in the example above, the pseudo halftone image shown in Figure 5 may be changed to the one shown in Figure 6 by reduction processing. This may result in an all-black image. Further, when the pseudo halftone image is a dithered image, there is also a problem that a decrease (change) in the number of gradations occurs regularly, resulting in moiré.

Furthermore, in the invention of JP-A-60-142669, in order to prevent a decrease in the number of gradations, the coordinates are alternately cut into even-numbered digits and odd-numbered digits for each successive dither matrix position in the original image data area. In this case, in order to switch between even number digits and odd number digits,
A means for address translation is required, which may complicate the device and increase cost.

The present invention has been made in view of the above-mentioned problems, and its purpose is to maintain a constant image quality without reducing the number of gradations before and after reduction processing of an image that has undergone pseudo-halftone processing. The purpose of the present invention is to provide a processing device.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention provides an image processing apparatus that performs reduction processing on a pseudo-halftone image by reducing the reduction rate (q/p)x.
(q/p), when the number of gradations is n x n, from the original image subjected to pseudo halftone processing, it consists of p x n pixels in the main scanning direction and p x n pixels in the sub scanning direction (P x n) (pX
n) area cutting means for cutting out an area of pixels, and block cutting means for cutting out q×q blocks each consisting of n×n pixels from the area cutting means and outputting them to the reduced pseudo-halftone image memory means; The gist is that a reduction processing means is provided.

Effect: With the above configuration, the area cutting means cuts out blocks having the same number of pixels as the number of gradations from the pseudo-halftone original image in a number corresponding to the reduction ratio (this is defined as one area). Next, the block cutting means cuts out the area in units of blocks by the number of pixels corresponding to the reduction ratio. Each block is made up of the same number of pixels as the number of tones in the original pseudo-halftone-processed original image, so the tones of the original image are maintained within each block.
There is no decrease in the number of tones in the pseudo-halftone image after reduction processing,
Moreover, moiré does not occur.

Embodiment FIGS. 1 to 3 are diagrams for explaining an embodiment of an image processing apparatus according to the present invention and its operation.

In FIG. 1, numeral 11 is a pseudo-halftone original image memory in which an original image subjected to pseudo-halftone processing is stored, and 12 is a pseudo-halftone original image taken out from the pseudo-halftone original image memory and corresponds to the reduction ratio. a reduction processing unit that performs reduction processing, 13;
is a reduced pseudo halftone image memory that stores the reduced image obtained by the reduction processing section 12;

The reduction processing unit 12 includes an area cutting unit 14 that cuts out an image area in blocks of a predetermined number of pixels from the pseudo-halftone original image memory 11, and an area cut out by the area cutting unit 14. The block cutout section 15 cuts out the number of pixels according to the reduction ratio from the inside in block units.

Of these, the area cutting unit 14 sets the reduction rate to (q/
P) From the original image stored in the pseudo-halftone original image memo January 1st, (p x n) x (p x n) pixels consisting of p x n pixels in the main scanning direction and p x n pixels in the sub scanning direction. It is set to cut out the area.

In addition, the block cutting section 15 is a block cutting section 15.
From area 4, create a block of n×n pixels by qXq
It is set to cut out each image and output it to the reduced pseudo-halftone image memory 13.

The operation of the image processing apparatus having such a configuration will be described below. Here, when performing the reduction process, the number of gradations of the pseudo halftone original image is n-2, p = 2, q = 1
, that is, the reduction rate is (q/p)x (q/p)=1/4.

The pseudo halftone image memory 11 stores the pseudo halftone original image shown in FIG. 5 and described above in the description of the conventional example. The area cutting unit 14 is a pseudo-halftone original image memory 11.
Areas AI, A2 . Cut out A3 and A4. Second
The figure shows the area cut out by the area cutting unit 14 in units of blocks. The data in this area is input to the block extraction section 15. The block cutting unit 15 extracts one block Bll, B2 corresponding to the upper left corner from each area A1 to A4 of the area cutting unit 14.
1. Select B31 and B41. The data of the selected block is stored in the reduced pseudo halftone image memory 13.

Since these blocks are composed of the same number of pixels as the number of gradations of the original image subjected to pseudo-halftone processing, the gradation of the original image is maintained within each pronk. Therefore, the reduced pseudo-halftone image memory 13 outputs a reduced pseudo-halftone image in which the number of gradations does not decrease as shown in FIG. 3, and no moiré occurs.

As described in detail, according to the present invention, reduction is performed by thinning out in units of blocks each consisting of a number of pixels equal to the number of gradations of a pseudo-halftone image. A high-quality image can be obtained without the occurrence of chimoir due to a reduced key.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an image processing apparatus according to the present invention, and FIG. 2 is a diagram showing areas cut out by the area cutting section in the above embodiment in units of blocks.
FIG. 3 is a diagram showing an example of a pseudo halftone image subjected to reduction processing in the above embodiment, FIG. 4 is a block diagram showing an example of a conventional image processing device, and FIG. 5 is a diagram showing an example of a pseudo halftone image subjected to reduction processing. A diagram showing an example of an image. FIG. 6 is a diagram showing an example of an image obtained by simply reducing the original image of FIG. 5 using a conventional apparatus. 11... Memory for pseudo-halftone original image, 12... Reduction processing section, 13... Memory for reduced pseudo-halftone image, 14
...Area cutting part, 15...Block cutting part.

Claims (1)

[Claims] A pseudo-halftone original image memory means for storing an original image subjected to pseudo-halftone processing, and a reduction process for extracting the pseudo-halftone original image from the pseudo-halftone original image memory and performing reduction processing. and a reduced pseudo-halftone image memory means for storing an image reduced by the reduction processing means, and the reduction processing means calculates a reduction ratio by (q/p)×(q/p), When the number of gradations is n×n, from the pseudo-halftone original image memory means, it consists of p×n pixels in the main scanning direction and p×n pixels in the sub-scanning direction (p×n
) x (p x n) pixel area, and a block cutting unit that cuts out q x q blocks of n x n pixels from the area cutting unit and outputs them to the reduced pseudo-halftone image memory means. An image processing device comprising: means.