JPH0440752A - Image signal processor - Google Patents

Abstract

PURPOSE:To prevent the deterioration of picture quality even with an original which includes the binary and halftone images by identifying the binary and halftone image parts of an original information signal by means of an image area separation algorithm. CONSTITUTION:An image area separation part 2 receives an image area separation instruction and analyzes a halftone original information signal 7 inputted from an original scanning part 1. The presence of an edge is defined when the difference of density between an image to be processed and its left adjacent image exceeds a set level and also when the picture element to be processed has the maximum or least density level. Then a binary processing section is decided only when the end is detected within 2 - 6 images based on the edge that is first detected. Then a selection signal is outputted for selection of the binary image data and the pseudo halftone image data. Thus it is possible to obtain the image data where the binary and pseudo halftone images are mixed together and the binary or pseudo halftone image data through a selection part 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to image signal processing means. In particular, the present invention relates to a binary image signal processing means for a document containing both photographs and text.

〔overview〕

The present invention provides means for processing an image signal of a document in which a binary image and a halftone image coexist on the same page, by identifying the binary image portion and the halftone image portion of the document information signal. It is possible to perform processing suitable for both binary images and halftone images.

[Conventional technology]

Conventionally, binary processing or pseudo-halftone processing has been selected for each page, and it has been impossible to use binary processing and pseudo-halftone processing properly within the same page.

[Problem to be solved by the invention]

In this way, in the conventional example, it is not possible to use binary processing and pseudo-halftone processing separately on the same page, so in the case of a document in which binary images and halftone images coexist on the same page, the binary image area Another disadvantage is that the image quality of one of the halftone image areas is significantly inferior.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image signal processing apparatus that eliminates such drawbacks and is capable of processing even original documents containing a mixture of binary images and halftone images without causing image quality deterioration.

[Means to solve the problem]

The present invention includes a document scanning section that scans a document in which a binary image and a halftone image are mixed on the same page to generate a document information signal, and a document scanning section that performs binary image processing on the document information signal to generate a binary image. An image signal processing device comprising a binary processing section that generates an image signal, and a pseudo halftone processing section that performs halftone image processing on the document information signal to generate a pseudo halftone image signal. an image area separation unit that generates an identification signal for identifying the binary image portion and the halftone image portion of the image area; and a selection unit that selects the binary image signal or the pseudo halftone image signal based on the identification signal. It is characterized by: Here, when the image area separation unit detects a pixel indicating an edge again within a predetermined number of pixels from the first detected pixel indicating an edge, the image area separation unit converts the interval defined by these two pixels into the binary image unit. It is desirable to do so. Further, it is desirable that a pixel whose density difference between adjacent pixels exceeds a set value and a pixel whose density exceeds a preset limit density be used as the pixel indicating the edge.

[Effect]

By analyzing the document information signal output from the document scanning unit, pixels whose density difference between adjacent pixels exceeds a set value and pixels whose density exceeds a preset limit density are successively detected, and the difference between these pixels is detected. When the number of pixels is within a predetermined number, this pixel section is determined to be a binary image portion. Based on this determination, an identification signal is generated to identify the binary image portion, the halftone image portion, etc. Depending on this identification signal, either a binary image signal subjected to binary image processing or a pseudo halftone image signal subjected to halftone image processing is selected and output.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of this embodiment. As shown in FIG. 1, this example shows the relative density with respect to the binary processing original information signal 6 and the reference white level, which was processed so that the background density of the original was always at the innermost level by scanning the original. The original scanning section 1 outputs the halftone original information signal 7, and the halftone original information signal 7 inputted from the original scanning section 1 is analyzed to identify whether it is a binary image part or a halftone image part and distinguish them. An image area separation unit 2 that outputs signals to be separated; and a binary processing unit that performs binary image processing on the binary processing manuscript information signal 6 input from the manuscript scanning unit 1 and outputs a binary image signal. 3, a pseudo halftone processing section 4 that performs pseudo halftone processing on the halftone document information signal 7 inputted from the document scanning section 1 and outputs a pseudo halftone binary image signal; and a binary processing section 3. a selection section 5 that selects and outputs either the binary image signal inputted from the image area separation section 2 or the pseudo halftone binary image signal inputted from the pseudo halftone processing section 4, based on the separation signal outputted from the image area separation section 2; Equipped with. Here, since the outputs of the binary image processing section 3 and the pseudo-halftone processing section 4 and the outputs of the image area separation section 2 are synchronized pixel by pixel, the selection section 5 Alternatively, the output of the pseudo halftone processing section 4 can be selected.

That is, this embodiment includes a document scanning section 1 that scans a document in which a binary image and a halftone image are mixed on the same page to generate a document information signal, and a document scanning section 1 that performs binary image processing on the document information signal. It includes a binary processing section 3 that generates a binary image signal, and a pseudo halftone processing section 4 that performs halftone image processing on the document information signal to generate a pseudo halftone image signal, and further includes:
The means characterized by the present invention includes an image area separation unit 2 that generates an identification signal for identifying a binary image portion and a halftone image portion of the document information signal, and an image area separation unit 2 that generates an identification signal for identifying a binary image portion and a halftone image portion of the document information signal; Selection unit 5 for selecting the pseudo halftone image signal
Equipped with.

Next, the operation of this embodiment will be explained with reference to FIGS. 1 and 2. Upon receiving a command to start reading the original from a control unit (not shown), the original scanning unit 1 starts scanning the original;
Outputs the type of original information signal. Upon receiving an image area separation command from a control unit (not shown), the image area separation unit 2 analyzes the halftone original information signal 7 input from the original scanning unit 1 according to an algorithm described later, and separates the binary image area and halftone image area from each other. It identifies the image area and outputs the selected signal.

When receiving a command to output a binary image or a pseudo-halftone output from a control unit (not shown), the image area separation unit 2 outputs a signal for selecting one of the outputs in accordance with the command. 2, image data in which a binary image and a pseudo-halftone image are mixed, or either binary or pseudo-halftone image data is obtained from the selection unit 5.

Next, a processing algorithm of the image area separation unit 2 when receiving an image area separation designation from a control unit (not shown) will be described.

Manuscript information has the following characteristics.

(1) In text/line drawings, the density difference with the back shadow level is large and the edges are clear. (2) In text/line drawings, the distance from the starting edge to the ending edge may be about a few pixels. (3) In the halftone part, the density difference with the background level rarely changes sharply, and the edges are unclear; (4) In the halftone part, the distance from the starting edge to the ending edge is long.

This algorithm focuses on the above points and performs the following processing.

(1) The basic state of processing is pseudo halftone processing, (2)
Image area separation processing is performed in the main scanning direction, (3) Check pixels sequentially from the right side of the document, ■ Assume the first edge found to be the beginning of a character or line drawing part, ■ Follow the steps in Section 9. If the end is found between 2 and 6 pixels from the beginning (this number of pixels can be set to a different value),
Register the interval from the beginning to the end as the binary processing interval, and if it is not found, cancel the assumption of the beginning in section 9, and repeat ■ ■ and ■ to register the data of the binary processing interval for one main scanning line. (4) (
A selection signal between binary image data and pseudo-halftone image data is applied according to the binary processing interval data obtained in step 3). This is done by defining an edge when the density difference exceeds a preset value and when the pixel to be processed has the highest or lowest density.

〔Effect of the invention〕

As explained above, the present invention can automatically distinguish between binary image areas and halftone image areas by using the image area separation algorithm. This has the advantage that even for documents containing mixed images, processing can be applied to each area.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a flowchart showing the operation of the embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Original scanning section, 2... Image area separation section, 3... Binary processing section, 4... Pseudo halftone processing section, 5... Selection section, 6... Binary processing 7... Halftone original information signal.

Claims (1)

[Claims] 1. A document scanning unit that scans a document in which a binary image and a halftone image are mixed on the same page to generate a document information signal; and a document scanning unit that performs binary image processing on the document information signal. In an image signal processing device comprising a binary processing section that generates a binary image signal, and a pseudo halftone processing section that performs halftone image processing on the document information signal to generate a pseudo halftone image signal, the document an image area separation unit that generates an identification signal for identifying a binary image portion and a halftone image portion of the information signal; and a selection unit that selects the binary image signal or the pseudo halftone image signal based on the identification signal. An image signal processing device comprising: 2. When the image area separation unit detects a pixel indicating an edge again within a predetermined number of pixels from the first detected pixel indicating an edge, the image area separation unit determines an interval defined by these two pixels as the binary image unit. The image signal processing device according to claim 1. 3. The image signal processing device according to claim 1, wherein a pixel whose density difference between adjacent pixels exceeds a set value and a pixel whose density exceeds a preset limit density are used as pixels indicating the edge.