JPH0463586B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus that outputs an input image in the form of a dot matrix pattern.

BACKGROUND OF THE INVENTION In recent years, many image processing apparatuses that output images using dot matrix patterns, particularly hard copy apparatuses using laser beam printers, inkjet printers, thermal printers, etc., that can output halftone images have been proposed.

In these devices, since the dot itself is a binary image, it is common to create pseudo-halftones using halftone dot areas in order to express halftones.

However, if an entire image containing a mixture of character images such as type and halftone images is expressed in pseudo-halftones using halftone dot areas, there are problems such as the outlines of the characters becoming blurred and small characters not being able to be expressed. arise.

In order to solve this problem, an image in which text images and halftone images are mixed is divided into a text image area and a halftone image area, and the text image area is expressed with a binary dot pattern of small pixels. The tone image area may be expressed by the aforementioned pseudo-halftone dot pattern.

In order to do this, in conventional hard copy devices, the image to be printed is printed before printing.
A method has been proposed in which a character image area and a halftone image area are separated by an operator's own operation using a digitizer or the like by displaying the image on a CRT display.

However, this method involves processing by the operator himself, which is time-consuming for the operator, and
The image forming time is extremely long.

Purpose The present invention has been made in view of the above circumstances, and is an image processing device that outputs an input image in a dot matrix pattern. It is an object of the present invention to provide an image processing apparatus that can output an appropriate dot pattern image for an input image.

EXAMPLES Hereinafter, details of the present invention will be explained based on the drawings.
First, the principle of the present invention will be explained with reference to FIGS. 1 to 4.

Figure 1 shows an image sample. This image sample includes a halftone image 1 that includes halftones and displays the equipment as shown in the figure, and a halftone image 1 that displays the device as shown in the figure, and the word "NEW" in binary density such as black and white. A displayed binary character image 2 and a binary character image 2' displaying the characters "PRINTER" are included.

FIG. 2 shows an image obtained by binarizing the image of the image sample shown in FIG. 1 at a predetermined density value.

FIG. 3 shows an edge portion, which is the outer edge of a figure expressed with a predetermined density in the image of FIG. According to the present invention, this edge portion is detected, and the fourth edge portion is further detected.
The geometric center of gravity of the figure surrounded by the edge portion is detected as indicated by each point in the figure.

Furthermore, by sequentially calculating the distance between adjacent centers of gravity, a figure having periodicity among each figure is detected as a character image. According to this detection result, the character image is outputted in a dot pattern for character images, and the other parts are outputted in a dot pattern for halftone images.

Next, the principle of the present invention as described above will be realized. The configuration of a specific embodiment of the present invention is shown in FIG. 5, and details will be explained.

In the figure, the reference numeral 3 designates an image reading device, which scans and reads the image shown in FIG. 1, for example, and outputs an analog electrical signal according to the shading of the image. The digitization circuit 4 connected to this latter stage is
It is composed of an AD converter, converts an input analog electrical signal into a digital signal indicating the density of each pixel, and further outputs it to the image memory 5 and edge detection circuit 6 connected at the subsequent stage.

The image memory 3 is a memory that stores the entire read image as digital data, and stores density data at each address corresponding to the position of each pixel according to the input digital signal.

On the other hand, the edge detection circuit 6 is a circuit that detects the address of the pixel in the edge portion shown by the solid line in FIG. This is done by detecting the pixel address of the point of change where the change occurs.

A memory 7 is connected to the subsequent stage of the edge detection circuit 6, and stores the pixel address of the edge portion inputted from the circuit. This pixel address is read by the center of gravity detection means 8 connected after the memory 7.

The center of gravity detection means 8 detects the center of gravity indicated by a dot in FIG.
That is, the geometric center of gravity of the figure in FIG. 3 is detected. This is obtained from the pixel address data in the memory 7 by a calculation described later.

Further, an identification circuit 9 is connected to the downstream of the center of gravity detection means 8, and the circuit identifies whether the figure corresponding to each center of gravity is a halftone image or a binary character image. This process calculates two figures with periodicity from each figure by sequentially calculating the distance between adjacent centroids from the pixel address data of the centroids in the memory 7.
Identifies as a value character image.

The area of the figure identified as a binary character image through this identification is stored in a map memory 10 connected to the identification circuit 9.

The map memory 10 and the image memory 5 described above are connected to a dot pattern generation circuit 11. This dot pattern generation circuit 11 is a circuit that outputs a dot pattern of the entire image according to the data in the image memory 5 and map memory 10.

This circuit has, for example, 8×8 for outputting halftone images.
A dot matrix generation circuit for dots and a dot matrix generation circuit for small pixels such as 2×2 dots for outputting a binary character image are provided, and these two circuits are further selected according to the contents of the map memory 10. A control means for driving is provided.

Next, the operation of this embodiment having the above configuration will be explained.

First, assume that the image shown in FIG. 1 is read by the image reading device 3. The reading device 3 scans the image and outputs to the digitizing circuit 4 an analog electrical signal whose strength changes depending on the density of the image.

The digitizing circuit 4 converts the input analog electrical signals into 8-bit hexadecimal numbers for each pixel according to their strength, that is, the density of the image.
FF" is converted into 256 digital signals and output to the image memory 5 and edge detection circuit 6.

The image memory 5 stores the entire image by storing input digital signal data for each pixel at an address corresponding to the position of each pixel.

On the other hand, the edge detection circuit 4 checks whether the data value of the input digital signal for each pixel is higher or lower than a threshold value of ``80'' in hexadecimal notation, and detects pixels at changing points that cross the value of ``80''. address, i.e. "80"
Detects the address of the first pixel that exceeds 80 or the first pixel that divides 80. Here data "80"
corresponds to a predetermined density lower than the density of the binary character images 2, 2'.

The above operation corresponds to detecting the pixel address of the edge portion shown in FIG. The pixel address of the edge portion detected in this way is stored in the memory 7.

Next, from the data stored in the memory 7, the center of gravity detecting means detects the address of the pixel of the center of gravity indicated by a dot in FIG.

This detection method involves, for example, enclosing a figure surrounded by edge pixels, calculating a rectangle with two sides parallel to the main scanning line and the other two sides parallel to the sub-scanning line, and then There are methods such as calculating and using it as the center of gravity.

Next, the identification circuit 9 checks whether the detected center of gravity address has periodicity.

That is, the identification circuit 9 sequentially calculates the distance between adjacent centroid addresses and sequentially compares the distances.
Then, centroids whose distances are approximately constant are saved, and centroids whose distances are indeterminate are deleted.

To determine whether this distance is approximately constant, for example, if the difference in the distance between successively adjacent centroids is within twice the dot matrix size for outputting a binary character image, it is determined that the distance is approximately constant. This is done by

In this case, as shown in FIG.
Since only the centers of gravity of 2′ are at approximately constant intervals,
The centroids of the binary character images 2 and 2' are stored.

Thereafter, the graphic area including each saved center of gravity, that is, the area of the binary character images 2 and 2' in FIG. 3, is stored in the map memory 10.

Next, the dot pattern generation circuit 11 generates a map 10.
image memory 5 while referring to the data stored in the image memory 5.
The dot patterns of all images are sequentially output according to the stored data. In this case, referring to the contents of the map memory 10, for the binary character images 2 and 2', a 2.times.2 dot matrix generation circuit outputs an image as a dot pattern with small pixels and a clear outline. For the other portions including the halftone image 1, an 8.times.8 dot matrix generation circuit outputs an image in a dot pattern of pseudo halftone dots of, for example, 65 gradations.

According to the above operation, binary character images 2 and 2' are identified from all images of input image samples,
The image of that part is output as a dot pattern with small pixels and a clear outline, and the other part including the halftone image 1 is output as a dot pattern of pseudo halftone dots.

Incidentally, in the above embodiment, the periodicity of each figure was detected using the center of gravity of each figure surrounded by edges, but a geometric point similar to the center of gravity may be used instead of the center of gravity. For example, one vertex in a predetermined direction within a rectangle calculated when detecting the center of gravity may be used.

Effects As is clear from the above explanation, in the image processing device according to the present invention, the image content is determined based on the periodicity from each figure consisting of a density area of a predetermined or higher density area in the input image. By outputting images using a dot pattern for character images for some parts, and outputting images for other parts using dot patterns for halftone images, characters and intermediate images can be output in a short time without any processing by the operator. It is possible to output an entire image containing a mixture of tone images with expressions appropriate for each image.

[Brief explanation of drawings]

Figures 1 to 4 each explain the principle of the present invention. Figure 1 is an explanatory diagram showing an image sample, and Figure 2 is an illustration of an image obtained by binarizing the image in Figure 1 at a predetermined density. Figure 3 is an explanatory diagram showing the edge portion of each figure in Figure 2, Figure 4 is an explanatory diagram showing the geometric center of gravity of each figure, and Figure 5 is a block diagram showing the configuration of the present invention. be. 1... Halftone image, 2, 2'... Value character image, 3
...Image reading device, 4...Digitization circuit, 5...
...Image memory, 6...Edge detection circuit, 7...
...Memory, 8...Gravity center detection means, 9...Identification circuit, 10...Map memory, 11...Dot pattern generation circuit.

Claims (1)

[Claims] 1. Means for detecting edges of each figure consisting of a density area of a predetermined density or higher in a human image; means for detecting the geometric center of gravity of each figure or a point equivalent thereto by calculation from said edges; and said center of gravity or a point equivalent thereto means for detecting a figure having periodicity from each figure by distance calculation between points,
An image processing apparatus characterized in that it determines whether an input image is a character image or a halftone image according to the detection result of the detection means.