JPH06225122A - Image forming device - Google Patents

Abstract

PURPOSE:To improve the reproducibility of a picture in which a character picture and a photographic picture subjected to pseudo intermediate tone processing are mixed. CONSTITUTION:A photographic area processing section 2 divides one picture element of an input picture into two in both longitudinal and lateral directions into in total 4 picture elements so that the resolution of the picture element is made coincident with a write density of a recording system 6. A character area processing section 3 references a noted picture element and 5X5 picture elements therearound to make pattern matching with a preset pattern to convert the picture so that a character stroke in hatched lines is optimized and the resolution of the picture elements is coincident with the write density of the recording system 6. An area discrimination section 4 counts number of picture elements of four-picture element connection in the area of 5X5 picture elements and discriminates it that the center picture element of interest is a picture element of the character area when the count is a prescribed value or over to select an output of the character area processing section 3 and discriminates it that the picture element of interest is a picture element of a photographic area when the count is less than the prescribed value and the section 4 selects an output of the photographic area processing section 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for recording at a resolution different from that of an input image.

[0002]

2. Description of the Related Art Generally, when the writing density of a recording device such as a laser printer is higher than the pixel density of an original image,
Interpolate the pixels of the original image to correspond to the writing density,
Further, the quality of the character image is improved by performing the smoothing process on the edge of the diagonal stroke of the character.

Here, when the smoothing process is performed on the entire received image when the resolution of the binary image is converted so as to match the writing density, pseudo halftone processing is performed by the dither method or the error diffusion method on the transmitting side. Since the gradation property of the photographic image is impaired, if the smoothing process is performed with a pattern that does not easily deteriorate the gradation property of the halftone image in order to prevent this, the smoothing process cannot be performed on the character image with the optimum pattern.

In a conventional facsimile apparatus, for example, as disclosed in Japanese Patent Laid-Open No. 3-254276, an input image is separated into a character image and a halftone image, and the resolution of only the character image is converted to perform smoothing processing. It is configured.

In another image forming apparatus, for example, as shown in Japanese Patent Laid-Open No. 1-218173, an image is separated into a density gradation image and an area gradation image, and gradation is performed with a dither pattern suitable for each image. By processing, the sharpness of any image is improved, and the shaded characters are also reproduced sharply.

[0006]

However, in the conventional method disclosed in Japanese Patent Laid-Open No. 3-254276, since the resolution of only the character image is converted and the smoothing process is performed, the gradation of the halftone image is destroyed. However, there is a problem that the resolution cannot be converted without using it.

In view of the above-mentioned conventional problems, it is an object of the present invention to provide an image forming apparatus capable of improving the reproducibility of an image in which a character image and a pseudo-halftone processed photographic image are mixed.

[0008]

In order to achieve the above object, the first means is to make a recording means for recording at a resolution different from that of the input image, and to make each pixel of the input image match the resolution of the recording means. And a second resolution conversion means for dividing each pixel of the input image so as to match the resolution of the recording means, and for smoothing the divided pixels at the edge of the diagonal stroke of the character image. Means for determining whether the input image is a character image portion or a photographic image portion, and in the case of a photographic image portion, the recording means records the pixels divided by the first resolution conversion means, and in the case of a character image portion, And a determining unit that controls the recording unit to record the pixels smoothed by the second resolution converting unit.

The second means is that the first resolution conversion means of the first means determines the divided pixel pattern of the target pixel by referring to the peripheral pixels of the target pixel of the input image when converting the resolution. Is characterized by performing halftone processing.

In a third means, the first resolution converting means of the first means converts the pixel of the binary input image into a multi-valued filter and the multi-valued filter. A resolution conversion unit that converts multi-valued data so as to match the resolution of the recording unit, and the multi-valued data whose resolution has been converted by the first resolution conversion unit is binarized to be converted into a pseudo halftone image. It is characterized by having a quantizing unit.

[0011]

In the first means, the pixels of the photographic image are divided so as to match the resolution of the recording means, and the character image is smoothed, so that the character image and the pseudo-halftone processed photographic image are mixed. The reproducibility of the formed image can be improved.

In the second means, halftone processing is performed by determining the divided pixel pattern of the pixel of interest when converting the resolution of the photographic image, so that the photographic image is more natural than the input image with increased gradation. It can be recorded as a halftone image.

In the third means, since the photographic image is subjected to pseudo halftone processing so as to match the resolution of the recording means, the photographic image is recorded as a more natural halftone image with increased gradation than the input image. be able to.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an embodiment of an image forming apparatus according to the present invention, FIG. 2 is an explanatory view showing an input example of a character image and a pseudo-halftone image, FIG. 3 is an explanatory view showing a smoothing process of a character image, FIG. 4 is an explanatory diagram showing the processing of the pseudo halftone image.

In FIG. 1, binary image data in which a character image and a quasi-halftone-processed photographic image are mixed is processed by the photographic area processing unit 2 and the character area processing unit 3, respectively, and also by the area determination unit 4. It is determined whether it is a photographic image or a character image. Then, the image data processed by the photograph area processing unit 2 and the character area processing unit 3 is selected by the selection unit 5 based on the determination result of the region determination unit 4, and the selected image data is transmitted via the recording system 6. Is recorded on the recording paper. Here, as an example, the writing density of the recording system 6 will be described as being twice the resolution of the input image.

First, the area determination algorithm of the photograph portion and the character portion of the area determination portion 4 will be described. Here, recently, when a multi-valued image is read by a scanner and binarized, the photo part and the character part are separated, and the photo part is processed by a pseudo halftone process using an error diffusion method or a dither processing method.
The image is converted into a binary image, while the character portion is subjected to edge enhancement processing and then converted into a binary image.

FIGS. 2A and 2B show examples of pixels of a character image and a pseudo-halftone image in which the number of black pixels is the same. In the character image, the strokes cross vertically and horizontally so that the pixels are vertically and horizontally. In many cases (4 connections), and in many cases, in a photographic portion subjected to pseudo halftone processing, it is often connected obliquely.

Therefore, the area determination unit 4 counts the number of pixels connected in four in the area of 5 × 5 pixels shown by the broken line in FIG. 2, and when the count value is equal to or more than a predetermined value, the pixel of interest in the center is determined. If it is less than a predetermined value, it is determined that the pixel of interest is a pixel in the photo area.

Returning to FIG. 1, in the photographic area processing unit 2, one pixel of the input image input from the input system 1 is divided into two vertically and horizontally so that the pixel resolution matches the writing density of the recording system 6. 4 pixels in total, and on the other hand, the character region processing unit 3 refers to the pixel of interest of the input image and its surrounding 5 × 5 pixels to match a preset pattern, and as shown in FIG. The stroke is optimized and the pixel resolution is converted to match the writing density of the recording system 6.

Therefore, according to the above embodiment, when the writing density of the recording system 6 is, for example, twice the resolution of the input image, the resolution of the photographic image is converted to double, and
Since the resolution of the character image is doubled and the edges of the diagonal strokes are smoothed, the reproducibility of the image in which the character image and the pseudo-halftone processed photographic image are mixed can be improved.

In the above embodiment, the resolution of the photographic image is only doubled, but as shown in FIG. 4, the pixel of interest of the input image and its peripheral 5 × 5 pixels are referred to in advance. The resolution may be doubled by matching the set pattern and determining the pattern of the divided pixels. The pattern in this case is different from the above-mentioned character pattern, and by using a pattern having good gradation reproducibility, the reproducibility of the quasi-halftone processed photographic image can be further improved. A soft image can be obtained by preventing the texture peculiar to processing from standing out.

Next, a second embodiment will be described with reference to FIGS. FIG. 5 is a block diagram showing a photograph area processing unit 2a, which is an essential part of the second embodiment, FIG. 6 is an explanatory diagram showing the multi-valued filter of FIG. 5, and other configurations are shown in FIG. Since they are the same, description thereof will be omitted.

In the multi-valued filter 7, one pixel is converted into multi-valued data by convolving the input image with a filter of 3 × 3 matrix as shown in FIG. Then, the resolution conversion unit 8 divides one pixel in both the vertical and horizontal directions into double to convert it into double resolution, and the binarization processing unit 9 further adjusts the resolution to match the resolution of the recording system 6.
It is digitized, converted into a pseudo halftone image, and output to the selection unit 5. In this case, the pseudo halftone process uses an error diffusion method or a dither method used in a scanner or the like.

Therefore, according to this second embodiment,
Since the photographic image is converted so as to match the resolution of the recording system 6 and the pseudo halftone processing is performed, it is possible to convert the image into a finer and smoother image than the input image. Since the image is recorded with a combination of pixels, it is possible to convert the image into a more natural halftone image having better gradation than the input image. Further, it is possible to prevent the texture peculiar to the pseudo halftone processing from being conspicuous and obtain a soft image.

[0025]

As described above, according to the first aspect of the invention, recording means for recording at a resolution different from that of the input image and each pixel of the input image are divided so as to match the resolution of the recording means. First resolution conversion means, and second resolution conversion means for dividing each pixel of the input image so as to match the resolution of the recording means and for smoothing the divided pixels of the edge of the diagonal stroke of the character image,
It is determined whether the input image is a character image part or a photographic image part, and when the input image is a photographic image part, the recording means records the pixels divided by the first resolution converting means, and when the input image is a character image part, the second image is recorded. Since the recording means controls the pixels smoothed by the resolution converting means to be recorded by the recording means, the pixels of the photographic image are divided so as to match the resolution of the recording means and the character image is displayed. Therefore, it is possible to improve the reproducibility of an image in which a smoothing process is performed, and thus a character image and a pseudo-halftone photographic image are mixed.

According to a second aspect of the present invention, when the first resolution converting means according to the first aspect converts the resolution, the divided pixel pattern of the target pixel is determined by referring to the peripheral pixels of the target pixel of the input image. By doing so, halftone processing is performed, so that it is possible to record a photographic image as a more natural halftone image with increased tonality than the input image.

According to a third aspect of the present invention, the first resolution converting means according to the first aspect converts a pixel of a binary input image into a multi-valued filter, and the multi-valued filter. A resolution conversion unit that converts the generated multi-valued data so as to match the resolution of the recording unit, and the multi-valued data whose resolution has been converted by the first resolution conversion unit is binarized and converted into a pseudo halftone image. Since it has a binarizing unit, it is possible to record a photographic image as a more natural halftone image with increased gradation than the input image.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing an input example of a character image and a pseudo halftone image.

FIG. 3 is an explanatory diagram showing a smoothing process for a character image.

FIG. 4 is an explanatory diagram showing processing of a pseudo halftone image.

FIG. 5 is a block diagram showing a photographic area processing unit which is a main part of the second embodiment.

FIG. 6 is an explanatory diagram showing the multi-valued filter of FIG. 5;

[Explanation of symbols]

 2, 2a Photographic region processing unit 3 Character region processing unit 4 Region determination unit 5 Selection unit 6 Recording system 7 Multi-valued filter 8 Resolution conversion unit 9 Binarization processing unit

Claims (3)

[Claims] 1. A recording means for recording at a resolution different from that of the input image, a first resolution converting means for dividing each pixel of the input image so as to match the resolution of the recording means, and each pixel of the input image. Second resolution conversion means for performing division so as to match the resolution of the recording means and smoothing the divided pixels at the edges of diagonal strokes of the character image, and determining whether the input image is the character image part or the photographic image part In the case of a photo image portion, the recording means records the pixels divided by the first resolution converting means, and in the case of a character image portion, the pixels smoothed by the second resolution converting means are the recording means. An image forming apparatus comprising: a determination unit that controls the recording so that the image is recorded. 2. The first resolution conversion means performs halftone processing by determining a divided pixel pattern of a target pixel with reference to peripheral pixels of the target pixel of the input image when converting the resolution. The image forming apparatus according to claim 1. 3. The first resolution conversion means stores a multi-valued filter for converting pixels of a binary input image into multi-valued data, and multi-valued data converted by the multi-valued filter in the recording means. A resolution conversion unit that converts the resolution so as to match the resolution, and the multivalued data whose resolution has been converted by the first resolution conversion unit is binarized and converted into a pseudo halftone image.
The image forming apparatus according to claim 1, further comprising a digitizing unit.