JPH0338782A - Detector for density of original - Google Patents

Abstract

PURPOSE:To generate a density histogram with high accuracy by generating the density histogram from the density data of a picture element in the area of an original based on the shape of the original detected with an original shape detecting means. CONSTITUTION:When the original is the one in which read data obtained by scanning the original is suppressed to the original mat of halftone color with a binarizing means 2, it is binarization-processed with different two threshold values. On the other hand, when the original is the one supressed to the original mat of black color, a binarization processing is performed with one threshold value, and it is stored in a storage means 3, and is realized with a processing program stored in advance in the memory of a central control part 10, and the shape of the original is detected with the original shape detecting means. And the density histogram is generated from the density data of the picture element in the area of the original with the data processing means 13, 10 based on the detected shape of original. Thereby, a precise density histogram can be generated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a document density detection device that can be used in image processing devices such as digital copying machines and fusing machines, and more specifically, the present invention relates to a document density detection device that can be used in image processing devices such as digital copying machines and fusing devices. The present invention relates to a device for creating a density histogram for determining a threshold value used when determining a density histogram.

[Prior art]

2. Description of the Related Art Conventionally, for example, in facsimile machines, digital copying machines, and the like, when performing image processing on a document, image data is binarized in advance. The threshold value for performing this binarization process is either fixed or specified on the operation panel.

Therefore, in recent years, for example, Japanese Patent Application Laid-Open No. 61-45679 has proposed the above-mentioned method to enable accurate image processing according to the state of the image even if there are variations in pencil shading and writing pressure in the manuscript. An apparatus has been proposed that has a function of automatically setting a threshold value in binarization processing according to the state of the image.

That is, in the apparatus disclosed in the above publication, a density histogram for each pixel of the original is created from the image data, and the white color is A binarization level, that is, a threshold for binarization, that maximizes the inter-region variance between the area and the black area is calculated, and the image data is binarized and recorded according to the binarization level. It is something.

[Problem to be solved by the invention]

However, with conventional devices such as those described above, when reading image data by scanning the optical system, the data is read not only from the original document but also from the surface of the original mat that holds the original document as an image, so the density is This has the disadvantage that the reliability of the histogram itself is significantly reduced.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a document density detection device that can detect the shape of a document and create an accurate density histogram from density data of pixels within a region of the document.

[Means to solve the problem]

In order to achieve the above-mentioned object, the main means adopted by the present invention is to obtain each of the originals from image data obtained by scanning the original held by a black or predetermined intermediate tone original mat. A document density detection device for creating a density histogram regarding pixels, the device comprising: a binarization processing means for binarizing the read data obtained in the reading scan using 1 or two different thresholds; and the binarization processing means. a storage means for storing the obtained data;
a document shape detection means for detecting the shape of the document from the data stored in the storage means; and a density histogram based on the density data of pixels within the region of the document based on the document shape detected by the document shape detection means. The data processing means for creating a data processing means is provided. ＆'1
This is a llJ degree detection device.

[Effect]

In the document density detection device according to the present invention, the read data obtained by scanning the document is binarized by the binarization processing means with one or two different threshold values, and this data is stored in the storage device. Ru.

In addition, when scanning a document pressed by a medium-tone document mat, the above-mentioned read data is binarized using two different threshold values (for example, the bits corresponding to the black and white area of the document are set to 1. The bit corresponding to the key area is classified as O). On the other hand, when scanning a document held down by a black document mat, the above-mentioned read data is binarized using one threshold value (for example, the bits corresponding to the white area of the document are converted to 1. The bit corresponding to the area is set to 0.

Then, the shape of the original is detected by the original shape detection means from the data stored in the storage means.

Subsequently, based on the document shape detected by the document shape detection means, a density histogram is created by the data processing means from the density data of pixels within the area of the document.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples embodying the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. It should be noted that the following examples are examples embodying the present invention, and are not intended to limit the technical scope of the present invention.

Here, FIG. 1 shows the configuration of a document density detection device according to an embodiment of the present invention. FIG. 2 is a flowchart showing the procedure for detecting the shape of a document relative to the document mat by the document density detection device, and FIG. 3 is an explanatory diagram for detecting the shape of the document relative to the document 77).

The document density detection device according to this embodiment is shown in FIG.
(As shown in BL and FIG. 3, for example, an optical system (not shown) is scanned against a document held down by a medium-tone document mat 1 (even if the optical system is moved or the document table is moved) The read data obtained by
Binarization processing means 2 for converting into values, storage means 3 for storing the data obtained by the above-mentioned binarization processing means 2, and document shape detection for detecting the shape of the document from the data stored in the above-mentioned storage means 3. and data processing means for creating a density histogram from density data of pixels within an area of the original based on the original shape detected by the original shape detection means.

In addition to the above-described configuration, the apparatus of this embodiment also includes an image data output section 4 that performs image processing according to a threshold value set based on the density histogram created by the data processing means.

In the binarization processing means 2, the read data obtained by scanning the optical system is compared with a first threshold T in the first comparison section 5, and further, the read data obtained by scanning the optical system is compared with a first threshold T in the second comparison section 6.
is compared with the threshold value T2.

Then, each data is applied to the AND gate 7, and the read data of the first threshold T, the smaller value is the white binoto 1, the second
Read data having a value larger than the threshold value T2 is treated as black bit 1. Further, read data having a value larger than the first threshold value T1 and smaller than the second threshold value T2 is extracted as halftone bit 0. In this case, with respect to the intermediate tone original matte 1, the peripheral edge and ground color of the original are white, so the first threshold T and the second threshold T2 are used to clearly distinguish the difference between these colors. It is set in advance to a predetermined value that can be classified into .

The above-mentioned read data is obtained by converting an output signal from, for example, a CCD line sensor constituting the scanner section 8 into digital data by an A/D converter, and converting the above-mentioned two data into density data in which one dot is divided into, for example, 256 gradations. It is input to the value conversion processing means 2. In this case, in order to reduce the amount of information stored, the read data is sampled at a frequency of 1/8, for example, and input to the binarization processing means 2.

Then, during 19 image processing, the image information is read again by the scanner section 8, and is output to the image data output section 4 through the image processing section 9 (for example, a unit 7 that processes data for character images and photographic images). . Then, the image data output section 4 operates according to the threshold determined based on the density histogram created by the data processing means.

The document shape detection means and data processing means are realized by a processing program stored in advance in a memory within the central control unit 10.

The image data output section 4 is constituted by a logic circuit including a plurality of gates, and outputs, for example, a text image or a photographic image according to a threshold determined based on a density histogram created by the data processing means. Corresponding image processing is performed sequentially and selectively at high speed. In this case, image processing is carried out by, for example, changing the pattern of the dither matrix and controlling on/off the laser emitting section constituting the printer section 11 according to this pattern.

Continuing, based on FIG. 1(a), FIG. 2, and FIG. 3,
The storage means 3 is binarized by the binarization processing means.
A procedure for detecting the shape of a document based on data stored in the document will be described.

In addition, in FIG. 2, Sl, S2. ...indicates each operation step.

First, at Sl, an address is set for the data in the storage means 3 at the origin of the area to be scanned by the central control unit 10.

Subsequently, if it is determined in S2 that the first data is 0 (normally, scanning is performed on the data in the portion corresponding to the document mat first, so it is O), the data is scanned on the front side in the main scanning direction (see Figure 3). ), a search is performed for the point where the data changes from 0 to 1 (S3), and if the point where the data changes from 0 to 1 is detected (S4), in S5, the distance of 1 in the main scanning direction is searched. A search is performed to see if they exist consecutively.

When it is determined that data 1 is continuous for a predetermined number of bits or more (S6), the address is entered at the change point in S7, and the beginning part is determined to be the starting point of the black and white area indicating the document. A judgment will be made.

If it is determined in step S6 that 1s are not continuous for a predetermined number of bits or more, a search is performed in step S8 to find out how many 1s are continuous in the front and back direction of the sub-scanning direction. If it is determined that the predetermined number of bits or more are not consecutive (39), it is determined that the data expressed as 1 is for dirt, etc. on the document mat, and the data is changed to 0. It is converted (S10).

When the edge of the document is detected in S7 as described above, the data is changed from 1 to 0 in the main scanning direction in 311.
A search for a change point is performed.

If it is determined that the data has changed from 1 to O (S12), a search is performed to find out how many consecutive 0s there are in the front direction in the main scanning direction (S13).

Then, if it is determined that the number of O's in the data is equal to or greater than a preset number of consecutive bits (S14), the address is set to the change point (S15), and the address is set to the point immediately before the change point. A determination is made that the bit is at the 1&end of the document with respect to its main scanning direction.

On the other hand, if it is determined in S14 that 0s do not continue for a predetermined number of bits or more, a search is performed in S16 to find out how many 0s are consecutive in the front-rear direction of the sub-scanning direction. If it is determined that O's are not continuous for a predetermined bisoto number or more, the data is converted to 1 based on the determination that the part is a halftone area part on the document (818).

When the scanning lines are sequentially incremented as described above and it is determined that processing for all lines has been completed (S
19), all data within the area surrounded by 1 data is converted to 1 so as to represent the outline of the original (320)
.

As a result, even a relatively large halftone region of a photograph, etc., present in the document is recognized as part of the document.

In this way, a map of the portion representing the original with respect to the original mat l is formed in the storage means 3.

Subsequently, based on the document shape detected as described above, a density histogram is created from the density data of pixels within the area of this document.

In this case, the image data for the entire scanning area of the optical system, which is the basis of the density data of pixels within the area of the original document, is as follows:
Processing is performed in the concentration detection section 13.

That is, in the density detection section 13 (see first output), image data regarding the entire scanning area of the optical system read by the scanner section 8 is sampled at a frequency of 1/8, and is stored in the memory 14. Ru. The image data stored in the memory 14 is compared in a predetermined number of stages of comparison sections 15 and classified into a predetermined number of gradations. The image data classified into a predetermined number of gradations is counted by a plurality of counting units 16 provided for each gradation based on map data of the document shape formed in the storage means 3, The frequency of occurrence of that density in each gradation is tallied.

Based on the density 1 occurrence frequency data for each gradation obtained as described above, the central control unit 10 creates a density histogram for the density data of pixels within the area of the document.

Then, based on the density histogram, an optimal threshold value for the document is calculated, and the image data output section 4 is controlled according to this threshold value.

As a result, optimal image processing corresponding to the image quality of the document is sequentially and selectively performed at high speed.

Therefore, according to the apparatus of this embodiment, it is possible to create an extremely highly accurate density histogram from the density data of pixels within the area of the original, and therefore the threshold value calculated based on this density histogram also corresponds to the image quality of the original. The optimum value can be set as follows.

In the above embodiment, an example was explained in which a medium-tone original mat was used, but it is also possible to construct the apparatus of this embodiment using a black original mat.

In this case, the threshold value used in the binarization processing means 2 is 1
In this binarization processing means 2, the black area of the document mat and the document may be 0. The black and white areas of the document are treated as 1 and binarized.

[Effects of the Invention] As described above, the present invention provides document density detection that creates a density histogram for each pixel of a document from image data obtained by scanning a document pressed by a document mat of black or a predetermined intermediate tone. The apparatus comprises a binarization processing means for binarizing the read data obtained by the reading scan using l or two different threshold values, and a storage means for storing the data obtained by the binarization processing means. , a document shape detection means for detecting the shape of the document from the data stored in the storage means; and a document shape detection means for detecting the shape of the document from the data stored in the storage means; Since the document density detection device is characterized in that it is equipped with data processing means for creating a histogram, it is possible to create an extremely highly accurate density histogram from the density data of pixels within the area of the document.

[Brief explanation of drawings]

FIG. 1 shows the configuration of a document density detection device according to an embodiment of the present invention, and +al in the figure is an overall block diagram. The figure (bl is a detailed block diagram of the density detection section, Figure 2 is a flowchart showing the procedure for detecting the shape of the original with respect to the original mat by the above-mentioned original density detection device, and Figure 3 is a flowchart showing the procedure for detecting the shape of the original with respect to the original mat). It is an explanatory diagram in the case of detection. [Explanation of symbols] 1... Original mat 2... Binarization processing means 3.
...Storage means 5...First comparison section 6...Second
Comparison section 7...AND gate 10...Central control section 13...Concentration detection section 14...Memory
15... Comparison section 16... Counting section

Claims (1)

[Scope of Claims] 1. A document density detection device that creates a density histogram for each pixel of a document from image data obtained by scanning a document pressed by a black or predetermined intermediate tone document mat, Binarization processing means that binarizes the read data obtained by the reading scan using one or two different threshold values; a storage means that stores the data obtained by the binarization processing means; a document shape detection means for detecting the shape of the document from the stored data; and data for creating the density histogram from density data of pixels within the area of the document based on the document shape detected by the document shape detection means. 1. A document density detection device comprising: processing means.