JPH01168162A - Picture area discrimination method in halftone mode - Google Patents

Abstract

PURPOSE:To sent a data sharply even if a thin character is expressed by comparing a signal level of an analog picture signal of one line with a discrimination reference value by a picture area discrimination circuit, comparing a binary slice level and an analog picture signal one by one picture element when a character area is discriminated and outputting the result. CONSTITUTION:A one-line analog picture signal outputted from an automatic gain control circuit 3 is inputted to a picture area discrimination circuit 4, subject to integration processing and a voltage level of the input signal is compared with a discrimination reference value. When a signal higher than the discrimination reference value exists, it is discriminated as the character area, a timer in the circuit 4 is operated for a prescribed time, a slice level switching circuit 8 is connected to a binary slice level 11 and when a lower signal exists, it is identified as a picture area, and the slice level changeover circuit is connected to a dither matrix level 12. Then the analog picture signal is compared by a comparator 13 one by one picture element each in response to the slice level and the result is sent as a digital picture signal. Thus, even if picture area and character area exist in mixture, the expression of a thin character can be attained.

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining an image area in a halftone mode, which is effective for transmitting documents containing a mixture of character areas and image areas, mainly by facsimile machines.

[Conventional technology]

When sending catalogs, documents, or photographs using a facsimile machine,
Conventionally, devices have been used that change from the normal mode in which characters are printed in black on blank paper to a halftone mode suitable for image transmission. In this halftone mode, each matrix of nxn matrix is 1! It was displayed in either white or black depending on the degree, and gradation was expressed by changing the density of black. This method is called a dither matrix method or simply a dither method, and is widely used not only in facsimile machines but also in copying machines and the like. [Problems to be Solved by the Invention] If a document to be sent by facsimile in halftone mode using the dither method contains both an image area and a character area, such as a catalogue, fine character parts cannot be expressed in a matrix. As a result, some of the text may be missing, making it difficult to read. The present invention relates to an image area determination method in halftone mode aimed at solving the above problems. Measures to solve the K problem] Image a! in halftone mode! In order to transmit in detail a document containing a mixture of areas and character areas, one line of analog image signal output from the automatic gain control circuit is input to an image area determination circuit consisting of an integrator, a comparator, and a timer. Both signal levels output from the analog image signal integrator are compared with the judgment reference value, and if the image signal level has a signal higher than the judgment reference value, the timer is activated for a predetermined period of time, and the dither matrix level is set to 2. A slice level switching circuit that selects whether it is a value slice level by a signal is connected to the binary slice level, and if the image signal level is a signal lower than the determination reference value, the slice level switching circuit is connected to the dither matrix level. The analog image signal of one line outputted from the automatic gain control circuit is compared pixel by pixel by a comparator according to the slice level of the slice level switching circuit, and is sent out as a binary image signal. K Effect: One line of analog image signal output from the automatic gain control circuit is input to the image area determination circuit, where it is integrated and the voltage level of the input signal is compared with a determination reference value. If there is a signal whose input signal level is higher than the determination reference value, it is identified as a character area, a timer in the circuit is activated for a predetermined period of time, and at the same time, the slice level switching circuit is connected to the binary slice level. On the other hand, if the input signal level is lower than the judgment reference value, it is identified as an image area,
Connect the slice level switching circuit to the dither matrix level. Depending on the slice level of the slice level switching circuit, one line of analog image signals outputted from the automatic gain control circuit are compared pixel by pixel by a comparator and sent out as a white or black digital image signal.

【Example】

A method for determining an image area in the bright halftone mode of the present invention will be described next along with a circuit for implementing the method. FIG. 1 is a block diagram of a circuit that determines an image area in halftone mode, and FIG. 2 is a waveform diagram showing an example of one line of analog image signal 1 in the main scanning direction output from the automatic gain control circuit. It is. The analog image signal of one line in the main scanning direction read by the charge-coupled device is inputted from the input terminal 2 to the automatic gain control circuit 3, given a predetermined gain, and controlled to the waveform illustrated in FIG. . This analog image signal 1 is output to an image area determination circuit 4 and a comparator 13, which will be described later. As shown in FIG. 3, the image area determination circuit 4 includes an integrator 5. Consisting of a comparator 6 and a timer 7, the comparator 6 compares the image signal level of the analog image signal output from the integrator with a preset judgment reference value, and makes the image signal level higher than the judgment reference value. If there is a high signal, it is determined that it is a character area and outputs [11; if the image signal level is lower than the determination reference value, it is determined that it is an image area and outputs rOJ. The timer 7 operates for about 8 bits corresponding to about 1 mtn when a signal of "1" is output from the comparator 6, and is used to continue the character area. The two contacts 9 and 10 of the slice level switching circuit 8 are configured to be switched by a binary signal output from the image area determination circuit 4. These two contact points 9 and 10 are
One contact 9 connects to the binary slice level input 11, and the other contact 10 connects to the dither matrix level input 12.
It is connected with. Then, either of these slice levels and each pixel of one line of analog image signal 1 output from the automatic gain 37 control circuit 3 are determined by the comparator 1.
3 and sent out from the comparator 13 as a binary image signal. Next, the operation of the image area determination method in halftone mode of the present invention when used in a facsimile machine will be explained based on the circuit shown in the block diagram above. When one line in the main scanning direction of the transmission original is read by the charge coupled device, this one line of analog image signal is sent to the input terminal 2.
The signal is then input to the automatic gain control circuit 3. In this automatic gain control circuit 3, a predetermined gain is given to the analog image signal. The analog image signal 1 to which gain has been applied is output to the image area determination circuit 4 and the comparator 13. In the image area determination circuit 4, the input analog image signal 1 is passed through an integrator 5.
performs integration processing and outputs to comparator 6. The comparator 6 compares the output signal from the integrator 5 with a preset determination reference value, and if a signal with a higher level than the determination reference value is detected, it determines that it is a character area, and the slice level switching circuit 8 Output "1" to the output terminal, connect it to the contact 9 to the input 11 of the binary slice level, and set the timer 7 to approximately 'Inm. Activate for a time corresponding to approximately 8 dots and continue the character area. Then, the comparator 13 compares the binary slice level with each pixel of the analog image signal 1 pixel by pixel, and sends out a binary image signal. On the other hand, the comparator 6 of the image area determination circuit 4 uses the integrator 5
When a signal outputted from is detected that is lower than the determination reference value, it is determined to be an image area, and rOJ is outputted to the slice level switching circuit 8 and connected to the contact 10 to the input 12 of the dither matrix level. , the dither matrix level and each pixel of the analog image signal 1 are compared pixel by pixel by a comparator 13, and a binary image signal is sent out.

【Effect of the invention】

In the method of the present invention, an image area determination circuit including an integrator, a comparator, and a timer compares the signal level of one line of analog image signal with a determination reference value, and selects a signal whose level is higher than the determination reference value, that is, a self-portrait signal. When detected, this area is determined to be a character area, and the binary slice level and analog image signal are compared pixel by pixel and output.
If the method of the present invention is applied to a facsimile machine that transmits originals containing a mixture of character areas and image areas, even fine characters can be clearly transmitted, making it ideal for transmitting characters in halftone mode. be.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a circuit implementing the method of the present invention, and FIG.
The figure is a waveform diagram of one line of analog image signal output from the automatic gain control circuit, and FIG. 3 is a block diagram of the image area determination circuit. 1...1 line analog image signal. 3... Automatic gain control circuit. 4... Image area determination circuit, 5... Integrator. 6... Comparator, 7... Timer. 8... Slice level switching circuit patent applicant Murata Kouki Co., Ltd. Agent Patent attorney Katsu Ohno Agent Patent attorney Reiko Ohno Agent Patent attorney Ryunosuke Ohno No. 2 Image area Text area

Claims (1)

[Claims] One line of analog image signal output from the automatic gain control circuit is input to an image area determination circuit consisting of an integrator, a comparator, and a timer, and the image signal level output from the integrator of the analog image signal and the determination reference value are input. If there is a signal whose image signal level is higher than the judgment reference value, the timer is activated for a predetermined period of time, and the slice level switching circuit that selects either the dither matrix level or the binary slice level based on the signal is activated. If the image signal level is lower than the determination reference value, the slice level switching circuit is connected to the dither matrix level, and the 1-line analog image output from the automatic gain control circuit is connected to the slice level. An image area determination method in halftone mode in which signals are compared pixel by pixel by a comparator according to the slice level of a slice level switching circuit and sent out as a binary image signal.