JPH06334863A - Picture processing unit - Google Patents

Abstract

PURPOSE:To obtain a picture processing unit without deteriorating picture quality of an output picture even when pseudo half tone threshold processed data are outputted with a printer of different type or model. CONSTITUTION:An input section 11 reads a picture of an original for each picture element and original picture data in plural bits are generated in the unit of picture elements. Said original picture data are subjected to gamma correction by a gamma correction processing section 12 and then by each of printer gamma correction sections 12 respectively. The sensor gamma correction processing section 12 applies gamma correction to the original picture data from the input section 11 corresponding to the gamma characteristic of the input section 11 to obtain picture data corresponding linearly to the picture density. Furthermore, a printer gamma correction processing section 14 applies gamma correction to the picture data from the sensor gamma correction processing section 12 corresponding to the gamma characteristic of an output section 6. Picture data from the printer gamma correction processing section 14 are fed to a half tone thresholding circuit 15, in which the data are threshold processed to be pseudo half tone threshold processed data and which are provided as an output to the output section 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing device.

[0002]

2. Description of the Related Art Conventionally, for example, in an image processing apparatus such as a facsimile, an image of an original is read by a scanner. The scanner has, for example, a CCD sensor in which a plurality of photoelectric conversion elements (CCD) are arranged in a line direction on a substrate, and the output voltage of each photoelectric conversion element is converted into digital original image data.

In this case, since the original image data is composed of analog data corresponding to the image density, it is pseudo-binarized by the halftone binarization circuit to be pseudo halftone binarized data. . By the way, in the image processing apparatus, the original image data is γ-corrected before being binarized in order to prevent the image quality of the output image from being deteriorated.

FIG. 2 is a diagram showing the relationship between the image density of the original and the output voltage of the photoelectric conversion element. In the figure, the vertical axis represents the output voltage of the photoelectric conversion element, and the horizontal axis represents the image density of the original. In the figure, the straight line a shows the theoretical output voltage of the photoelectric conversion element with respect to the image density of the original, and the curve b shows the actual output voltage with respect to the image density of the original. That is, when the image of the original is read by the scanner, an output voltage lower than the theoretical value is output.

Therefore, the original image data is γ-corrected so that the relationship between the image density and the output voltage as shown by the curve b becomes as shown by the straight line a.

[0006]

However, in the conventional image processing apparatus, when the pseudo halftone binarized data is output by the printer, the LED printer,
Since the γ characteristic of the output voltage differs depending on the type and model of the printer such as laser beam printer and thermal printer, there will be a considerable difference in the output image, and the output image will be blacked out or become too white. The image quality may deteriorate.

For example, in the case of an LED printer or a laser beam printer, since the dots are circular, the size of the dots is set large so that a white portion is not formed between the black pixels when outputting a black solid image. I try to overlap some of them. On the other hand, in the case of a thermal printer,
Since the dots are rectangular, the black pixels need only be adjacent to each other when solid black output is performed. for that reason,
When the pseudo-halftone binarized data is output by an LED printer or a laser beam printer, the image density of the output image is higher than when it is output by a thermal printer.

However, the correction data for γ-correcting the original image data is formed so as to correspond to a printer of a specific type or model selected in advance. Therefore, if the type and model of the printer of this machine and the printer of the other machine are different in the facsimile, if the data sent from this machine is output by the printer at the other machine, the transmission data is γ-corrected corresponding to the printer of this machine. Therefore, the image quality of the output image is deteriorated due to occurrence of blackout or excessive whitening.

On the contrary, when the received data from the partner is output from the printer by the printer, the received data is γ-corrected in correspondence with the printer of the partner, so that similarly, a black underexposure or white is generated. The quality of the output image deteriorates due to too much image quality. The present invention solves the problems of the conventional image processing apparatus described above, and even if the pseudo halftone binarized data is output using printers of different types and models, the image quality of the output image deteriorates. It is an object of the present invention to provide an image processing apparatus that does not have the image processing apparatus.

[0010]

To this end, in the image processing apparatus of the present invention, the input section reads the image of the original for each pixel and generates the original image data of a plurality of bits for each pixel. The original image data is r-corrected by the sensor γ correction processing unit, and then γ-corrected by the printer γ correction processing unit. The sensor γ correction processing unit performs γ correction on the original image data from the input unit in accordance with the γ characteristic of the input unit to obtain image data that linearly corresponds to the image density. The image data from the sensor γ correction processing unit is γ corrected according to the γ characteristic of the output unit.

Then, the image data from the printer γ correction processing section is sent to a halftone binarization circuit, and the halftone binarization circuit pseudo-binarizes the image data to generate a pseudo halftone binarization.
It is converted into digitized data and output to the output unit.

[0012]

According to the present invention, as described above, in the image processing apparatus, the input section reads the image of the original for each pixel,
A plurality of bits of original image data are generated for each pixel. The original image data is r-corrected by the sensor γ correction processing unit, and then γ-corrected by the printer γ correction processing unit. The sensor γ correction processing unit γ-corrects the original image data from the input unit in accordance with the γ characteristic of the input unit to obtain image data that linearly corresponds to the image density. In this case, the sensor γ correction data corresponding to the γ characteristic of the input section is used.

Further, the printer γ correction processing section γ-corrects the image data from the sensor γ correction processing section in accordance with the γ characteristic of the output section. In this case, the printer γ correction data corresponding to the γ characteristic of the output section that differs depending on the type of the output section is used. Then, the image data from the printer γ correction processing unit is sent to the halftone binarization circuit, which pseudo-binarizes the image data to generate the pseudo halftone 2
It is converted into digitized data and output to the output unit.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram of an image processing apparatus showing an embodiment of the present invention, and FIG. 3 is a conceptual diagram of a facsimile to which the image processing apparatus showing the embodiment of the present invention is applied. In FIG. 3, reference numeral 1 is a facsimile, 2 is a line connected to a telephone line network, a private line network, or the like (not shown), and 3 is a reception data from a partner device (not shown) or a transmission to the partner device via the line 2. A communication control unit for transmitting data, a general control unit 4 for controlling the entire facsimile 1,
Reference numeral 5 is a scanner for reading an image of a document for each pixel and generating pseudo halftone binarized data corresponding to the image density.
Is an output unit such as a printer which receives and outputs pseudo halftone binarized data from the scanner 5.

Therefore, the image of the original is read by the scanner 5 pixel by pixel, and the pseudo halftone binarized data corresponding to the image density is transmitted as transmission data to another facsimile or output by the output unit 6. You can Next, the image processing apparatus will be described. In FIG. 1, 6 is an output unit, 11 is an input unit, 12 is a sensor γ correction processing unit, 13 is a printer γ correction table receiving unit, 14 is a printer γ correction processing unit, and 15 is a halftone binarization circuit.

The input section 11 comprises an image reading device (not shown) such as a contact sensor and a CCD sensor, and a control part of the image reading device. For example, in a CCD sensor, a plurality of photoelectric conversion elements are arranged on a substrate in the line direction so that an image of a document can be read for each pixel, and each photoelectric conversion element has a different image density. Generate the corresponding output voltage. The photoelectric conversion element is connected to a shift register (not shown), and each output voltage is output in parallel to the shift register. Then, the output voltage is transferred in the line direction in the shift register and is serially output to the control unit.

Further, the control section has an A / D converter (not shown), which digitally converts the output voltage of the photoelectric conversion element into the sensor γ correction processing section 12 as pixel-by-pixel original image data. Output to. In this embodiment, 8-bit original image data is output. Then, the sensor γ correction processing unit 12 uses the input unit 11
When the original image data from is received, the original image data is γ-corrected in accordance with the γ characteristic of the input unit 11 to obtain image data.
Therefore, the sensor γ correction processing unit 12 has a sensor γ correction table corresponding to the γ characteristic of the input unit 11. In the present embodiment, the sensor γ correction table has sensor γ correction data for γ-correcting the original image data with an exponential function type curve to obtain image data linearly corresponding to the image density. That is, the sensor γ correction processing unit 12 makes the relationship between the image density and the output voltage shown by the curve b in FIG. 2 as shown by the straight line a.

Next, the image data that has been gamma-corrected by the sensor gamma correction processing unit 12 is output to the printer gamma correction processing unit 14, and the printer gamma correction processing unit 14 corresponds to the gamma characteristic of the output unit 6. Then, γ correction is performed. Therefore, the printer γ correction table receiving unit 13 is provided, and the printer γ correction table receiving unit 13 outputs the output unit 6
To receive the printer γ correction table. In the case of the facsimile 1 (FIG. 3), the printer γ correction table receiving unit 13 is provided in the communication control unit 3, and the communication control unit 3 operates during the NFS operation in which information regarding the type and model of the printer is transmitted. Upon receiving the received data, the printer γ correction table receiving unit 13 receives the printer γ correction table of the output unit of the partner machine. Then, the CPU (not shown)
The received printer γ correction table is loaded into the printer γ correction processing unit 14.

As described above, the printer γ correction table is made up of printer γ correction data corresponding to γ characteristics that differ depending on the type and model of the printer. For example, in the case of a thermal printer, the printer γ correction data is the number of black pixels. Since the image density per unit area is relatively linear, the printer γ correction data can be represented by a linear curve. Further, in the case of an LED printer or a laser beam printer, black crushing is likely to occur, so the printer γ correction data is represented by a curve that shifts the number of gradations on the black side to the white side.

In this way, the printer γ correction processing unit 1
Reference numeral 4 denotes the γ-correction of the image data based on the printer γ-correction data corresponding to the γ-characteristics different depending on the type and model of the printer, and the relationship between the image density and the output voltage is set as shown by the straight line a in FIG. Output to the halftone binarization circuit 15. Upon receiving the image data from the printer γ correction processing unit 14, the halftone binarization circuit 15 artificially converts the image data into 2 by using a systematic dither method, an error diffusion method or the like.
The data is binarized into pseudo-halftone binarized data, which is output to the output unit 6.

The output unit 6 is, for example, a printer, which receives the pseudo halftone binarized data and prints it on a recording sheet.
In the facsimile 1, the output unit 6 is a coding device when transmitting the transmission data to the partner device, and the output unit 6 is a printer when receiving the transmission data from the partner device.
The present invention is not limited to the above embodiment,
Various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

[0022]

As described above in detail, according to the present invention, in the image processing apparatus, the input section reads the image of the original for each pixel and generates the original image data of a plurality of bits in pixel units. The original image data is r-corrected by the sensor γ correction processing unit, and then γ-corrected by the printer γ correction processing unit. The sensor γ correction processing unit γ-corrects the original image data from the input unit in accordance with the γ characteristic of the input unit to obtain image data that linearly corresponds to the image density.
Further, the printer γ correction processing unit performs γ correction on the image data from the sensor γ correction processing unit in accordance with the γ characteristic of the output unit.

Then, the image data from the printer γ correction processing section is sent to a halftone binarization circuit, and the halftone binarization circuit pseudo-binarizes the image data to generate a pseudo-halftone binarization.
It is converted into digitized data and output to the output unit. Therefore, even if the output unit outputs the pseudo halftone binarized data by using the printers of different types and models, the image quality of the output image does not deteriorate.

[Brief description of drawings]

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

FIG. 2 is a relationship diagram between the image density of a document and the output voltage of a photoelectric conversion element.

FIG. 3 is a conceptual diagram of a facsimile to which the image processing apparatus according to the exemplary embodiment of the present invention is applied.

[Explanation of symbols]

 6 Output Section 11 Input Section 12 Sensor γ Correction Processing Section 13 Printer γ Correction Table Reception Section 14 Printer γ Correction Processing Section 15 Halftone Binarization Circuit

Claims (1)

[Claims] 1. An input unit for (a) reading an image of a document for each pixel and generating a plurality of bits of original image data in pixel units, and (b) the original image data from the input unit having a γ characteristic of the input unit. Corresponding to the sensor γ correction processing unit that makes γ correction corresponding to the image density and linearly corresponds to the image density, and (c) the image data from the sensor γ correction processing unit corresponds to the γ characteristic of the output unit. a printer γ correction processing unit for γ correction, and (d) halftone to be pseudo-binarized into image data from the printer γ correction processing unit to obtain pseudo halftone binarized data and output to the output unit. An image processing apparatus having a binarization circuit.