KR101015753B1 - Mobile terminal having a function of transmitting a document image and image converting method therefor - Google Patents

Abstract

The present invention relates to a mobile terminal having a document image transmission function and a document image conversion method therefor. The present invention provides a method and apparatus for increasing an image readability of a photographed document in order to fax a document photographed by a mobile terminal having a low resolution camera. After extracting the red, green, and blue values from each pixel of the color document image photographed by the camera provided in the mobile terminal, the extracted red, green, and blue values are converted into the luminance value Y and the color value U and V values. When the color value of each pixel is larger than a threshold value, the luminance value is corrected by multiplying the luminance value of the pixel by a predetermined weight less than one. After taking the method of converting the corrected luminance value into a black and white document image, the image is enlarged and interpolated to increase the readability of the document and transmitted to a predetermined communication network.

FAX, Bicubic, RGB, YUV

Description

MOBILE TERMINAL HAVING A FUNCTION OF TRANSMITTING A DOCUMENT IMAGE AND IMAGE CONVERTING METHOD THEREFOR}             

1 is a diagram illustrating a configuration of a mobile terminal having a document image transmission function according to an embodiment of the present invention.

2 is a flowchart illustrating a document image conversion method according to an embodiment of the present invention.

3 is a diagram illustrating a process of converting a color document image into a black and white document image according to an embodiment of the present invention.

4 is a diagram illustrating a process of transmitting a converted black and white document image to an external communication network according to an exemplary embodiment of the present invention.

The present invention relates to a mobile terminal equipped with a digital camera and an image processing method therefor. In particular, the readability of the document image is improved in a process of converting a color document image photographed from a mobile terminal having a low resolution camera into a black and white document image. The present invention relates to a mobile terminal having a document image transmission function, and a document image conversion method therefor.

In general, a mobile terminal is one that provides voice calls to users. However, at present, the mobile terminal has evolved to provide various services to users, and has also provided data services such as text messaging, photo or video services, and mobile banking. Among the mobile terminals, users of mobile terminals equipped with digital cameras may capture various images through the mobile terminal, and may transmit the captured images. In addition, the photographed image is used as a background screen or a photo mail of the mobile terminal as it is, or is edited and used through an image editing program of a personal computer. The camera may use a CCD or a CMOS sensor, and the display unit may use an LCD. The mobile terminal may capture and display a moving image and a still image by using the camera, and may also transmit the captured image to another mobile terminal. A representative example of document image transmission is fax transmission. In order to transmit a document image according to the related art, a proximity recognition camera, a high resolution camera, a scanning sensor, and the like are required, so that it is difficult to apply to the mobile terminal, and even if applied, expensive hardware is required.

On the other hand, when using a low-resolution image camera that is used in the past is not suitable for taking documents, etc. because it is impossible to take close-up photography and a lot of blur effect. In addition, due to the characteristics of the sensor, the captured image is noisy, and when a general black and white document is taken with a color camera provided in the mobile terminal and converted into a black and white image suitable for fax transmission, image loss is much. Therefore, the read rate of the photographed image is too low to transmit the document image photographed by the digital camera mounted in the conventional mobile terminal, and thus it could not be transmitted by fax.

An object of the present invention is to provide a mobile terminal for converting a color document image photographed with a low resolution camera into a black and white document image with improved readability and transmitted to the outside.

Another object of the present invention is to provide a method for converting a color document image photographed from a mobile terminal having a low resolution camera into a black and white document image having improved readability.

The mobile terminal of the present invention for achieving the above object comprises a digital camera for photographing a subject and a display unit for displaying an image received from the digital camera, and temporarily storing the color image photographed by the camera, A memory for storing red, green, and blue color values extracted from a color image, and storing luminance and color values extracted from the red, green and blue color values, and red for each pixel in the photographed color image. Extracting the green and blue color values, converting the extracted red, green and blue color values into the luminance and the color values, respectively, and checking whether the color value of each pixel is greater than or equal to a threshold value. A controller for correcting the luminance value and converting a color image into a black and white image using the corrected luminance value when the threshold value is greater than or equal to the threshold value; And a wireless unit for transmitting the converted monochrome image to a predetermined communication network.

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According to an aspect of the present invention, a method for converting a color image photographed by a mobile terminal having a digital camera into a black and white image includes luminance using red, green, and blue values in the color image. Extracting a value and a color value, comparing the color value of each pixel constituting the color image with a predetermined threshold value, and if the color value is greater than or equal to the threshold value, the luminance value is determined. And converting the color image into a black and white image with the corrected luminance value.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same components in the drawings represent the same numerals wherever possible.

Specific details are set forth in the following description, which is provided to aid a more general understanding of the invention. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The image converting method according to an embodiment of the present invention described below may be applied to devices having a digital camera and an image transmission function. In an embodiment of the present invention, a mobile terminal equipped with a camera will be described as an example. However, the present invention is not necessarily limited to a mobile terminal having a camera, and may be applied to any device capable of capturing an image having a microprocessor having a relatively low processing capacity and having a low resolution camera.

1 is a block diagram illustrating an internal configuration of a mobile terminal having a document image transmission function according to an embodiment of the present invention.

Referring to FIG. 1, the RF unit 100 includes an RF transmitter for upconverting and amplifying a frequency of a transmitted signal, and an RF receiver for low noise amplifying and downconverting a received signal. The data processor 102 includes a transmitter for encoding and modulating the transmitted signal, a receiver for demodulating and decoding the received signal, and the like. That is, the data processor 102 may be configured of a modem and a codec, wherein the codec reproduces a received audio signal output from a data codec for processing packet data and an audio codec such as voice. Or transmit a transmission audio signal generated from a microphone to an audio codec of the data processor 102. The data processing unit 102 may inform the user of whether to send a fax by voice after converting a black and white document image according to an exemplary embodiment of the present invention, and receives a voice from the control unit 106 to display a guide and a result of execution during another program. Process.

In FIG. 1, the key input unit 104 includes keys for inputting numeric and character information and function keys for setting various functions. In addition, the key input unit 104 may include function keys for controlling an image mode, a shooting key for driving the camera 114, and function keys for fax transmission.

The memory 108 of the mobile terminal may include a read only memory (ROM) and a random access memory (RAM). The memory 108 stores various temporary data generated during the processing of the controller 106 and user data such as a phone number, ring tone, and image information. In addition, the memory 108 includes a program for controlling a general operation of the mobile terminal, a process of converting a color document image into a black and white document image, a process of displaying the converted image on the display unit 110, and a document image according to the present invention. Certain programs for controlling a process of transmitting to an external communication network may be stored.

In addition, the memory 108 includes luminance (Y) and color converted from red (R), green (G), and blue (B) values of each pixel constituting the photographed color document image. Save the value (Chrominance: U, V). The captured color image is converted into a black and white image by using the extracted luminance and color values, and the controller 106 enlarges and interpolates and stores the black and white image.

The controller 106 performs a function of controlling the overall operation of the mobile terminal. According to an embodiment of the present invention, the control unit 106 extracts R, G, and B values from each pixel constituting the color image according to a mode command set from the key input unit 104, thereby Y, U, and V values. Convert to The controller 106 compares the U and V values, which are color values among the converted Y, U and V values, with a predetermined threshold value, and when the U and V values are equal to or greater than the threshold value, the controller 106 assigns a predetermined weight to the Y value which is a luminance value. Multiply by Here, the weight is determined by selecting an appropriate value in a range of less than one.

In the same manner as described above, the controller 106 converts the photographed color document image into a black and white document image, enlarges and interpolates the converted image, and transmits the image to a fax. In addition, the control unit 106 performs a function of outputting a specific state, that is, the arrival of a text message, the process of faxing a document image, the dialing state, and the data received from the camera 114 to the display unit 110. In addition, the control unit 106 may display a general operation state such as a current time, a reception sensitivity, a battery remaining amount, and the like on the display unit 110.

The camera 114 of FIG. 1 includes a camera sensor for converting an optical signal detected at the time of image capturing into an electrical signal, and a signal processor for converting an analog image signal photographed from the camera sensor into digital data. The camera sensor may be implemented as a CCD (Charge Coupled Device) sensor, the signal processing unit may be implemented with a DSP (Digital Signal Processor), and may be implemented with an image processing device other than the DSP. In addition, the camera sensor and the signal processor may be integrally implemented or may be separately implemented.

The image signal output from the camera 114 is applied to the image processor 112, and the image processor 112 performs a function of generating screen data such that the input image signal is displayed on the display unit 110. The image processor 112 processes the image signal output from the camera 114 in units of frames, and outputs the frame image data according to the characteristics and the size of the display unit 110. In addition, the color document image, which is the video signal input from the camera 114, is displayed on the display unit 110 with R, G, and B values, and the controller 106 controls the R, G, B values of the color document image. After the process of converting the image to Y, U, V to be described later, the converted black and white image is controlled to be displayed on the display unit 110.

The display unit 110 visually displays an image signal applied from the image processor 112. The display unit 110 may use a liquid crystal display (LCD). In this case, the display unit 110 may include an LCD controller, a memory capable of storing image data, and an LCD display element.

2 is a flowchart illustrating a document image conversion method according to an embodiment of the present invention, which converts a color document image photographed by the camera 114 into a black and white document image according to the present invention, and converts the converted black and white document image. Shows the process of transmitting and faxing through an external communication network by enlarging and interpolating.

Before the process of FIG. 2 is performed, the process of setting the camera to the camera photographing mode through the key input unit 112 must be preceded. The controller 106 displays an image input from the camera 114 on the LCD through the image processor 112, which is called a preview mode. If the controller 106 does not request to take a picture according to the operation state of the camera 114, the controller 106 continues to operate in the preview mode to show an image input from the camera 114 to the user. The image capturing method may be performed by first driving the camera 114 to perform a preview mode and then performing a capturing operation. The capturing operation may be performed simultaneously with driving the camera 114.

Then, when the user drives the camera 114 to take a subject, the image processor 112 detects this and performs a preview mode to display an image of a subject photographed through the camera 114 on the display 110. do.

When the user selects the document image transmission mode through the key input unit 104 in step 200 of FIG. 2, in step 202, the controller 106 drives the camera 114 to capture an image of an object specified by the user, that is, an original document. . The image signal of the color document image output from the camera 114 is transmitted to the image processor 112, and the image processor 112 sends the captured image to the display unit 104 to output the image. After the photographed image is displayed on the display unit 104, the user checks the state of the photographed color document image to determine whether to retake the image, and if the user wants to retake the image, repeats the operations after step 200. When the image of the desired state is photographed, the photographed image is stored in the memory 108 according to the user's key operation.

Thereafter, in step 206, the controller 106 extracts R, G, and B values of each pixel constituting the color document image stored in the memory 108, and in step 208, the R, G, and B values of each pixel are Y as luminance values. Convert to U and V values which are color values. In step 208, the process of converting the R, G, and B values into Y, U, and V values is performed using Equation 1 below, and the R, G, and B values are converted into Y, U, and V values. Since the conversion process is a general content, a detailed description thereof will be omitted.

Y = 0.299R + 0.587G + 0.11B

U = -0.147R-0.289G + 0.436B

V = 0.615R-0.515G-0.1B

Thereafter, in step 210, if the U, V values, which are color values among the Y, U, and V values converted in step 208, are greater than or equal to a threshold value, the controller 106 multiplies the Y value by a predetermined weight G value according to step 212. Output the luminance value Y '. This is to reduce the noise component of the Y value used in the conversion to the black and white image.

That is, by using Y, which is a luminance value among the Y, U, and V values converted through Equation 1, a color document image may be converted into a black and white document image. In this case, the color component of the color document image serves as a noise component of the black and white document image. That is, since the document image input from the camera 114 is color information, the document image has no color component. Accordingly, when the color values U and V are completely removed and converted into a black and white image using only the Y value as the luminance value, the pixel may be broken and the converted black and white document image may not be recognized.

Therefore, in the present invention, if the U, V value is greater than or equal to the threshold value to reduce the magnitude of the noise component mixed with the Y signal, the Y signal is corrected by multiplying the Y signal by a weight less than 1 to reduce the U, V value. The luminance value Y 'is obtained, and the corrected luminance value is used to convert the color document image into a black and white document image. Here, the weight makes the luminance value relatively higher than the color signal value, and the threshold value is obtained through Equation 2 below.

Threshold = average of all pixel luminance values-n

In general, the average value of the luminance signal is not suitable as the threshold value because it is larger than the color signal. Therefore, in Equation 2, an appropriate threshold value is determined by subtracting an n value, which is a predetermined correction constant, from an average value of the entire luminance values. This means that when the value of the color signal included in each pixel is greater than or equal to the threshold value, the color signal is reduced by reducing the color value by recognizing the actual color signal. Since the color value enters the luminance component as noise, the color component is reduced by multiplying the luminance component by a predetermined weight less than one.

In step 210, after the U and V values are smaller than the threshold value or the luminance value Y is corrected according to the step 212, the controller 106 determines the luminance value Y or the corrected luminance value corresponding to the pixel in step 214. Y 'is stored in the memory 108. In operation 216, the controller 106 determines whether the pixel in which the current luminance value is stored is the last pixel, and if it is not the last pixel, the operation of steps 206 to 214 until the luminance value or the corrected luminance value of the last pixel is obtained. Repeat to run.

 If the inspection is completed in step 216 to the last pixel, the flow proceeds to step 218 to generate a black and white document image using the Y value of each pixel. The black and white document image generated in step 218 is enlarged and interpolated in step 220. As a method of enlarging and interpolating, the bicubic method is typically used. In step 222, the black and white image enlarged and corrected in step 220 is transmitted to a predetermined receiver.

FIG. 3 illustrates a process of converting a color document image into a black and white document image according to an exemplary embodiment of the present invention. For the convenience of understanding, the document image illustrated in FIG. 3 assumes a 9 pixel image composed of 3 × 3. Reference numeral 300 denotes a color image composed of 9 pixels, and shows a process of extracting R, G, and B values from each pixel. Reference numeral 302 is a diagram illustrating a process of converting the R, G, and B values extracted from the image of step 300 into Y, U, and V values for each pixel. Is done through. Reference numeral 304 denotes the Y, U, V of each pixel after the steps 210 and 212 of FIG. 2 are performed using Equation 2 with respect to the Y, U, and V values converted by the reference numeral 302. , V value is displayed. In reference numeral 304, U, V values of color components of each pixel are greater than or equal to the threshold value, and the luminance value Y 'is corrected by multiplying the Y value by a weight smaller than 1 in the reference numeral 304. Giving.

4 illustrates a process of transmitting a converted black and white document image to an external communication network according to an embodiment of the present invention, which illustrates, for example, a process of transmitting a black and white document image by fax.

Reference numeral 401 illustrates a digital camera provided in the mobile terminal, and step 403 shows a color document image photographed from the camera. In step 405, a color document image of reference numeral 403 is converted into a black and white image. In step 405, as described above, R, G, and B values are extracted from each pixel of the color image, and then, for each pixel. After extracting Y, U, V values using Equation 1, the luminance value Y of each pixel using Equation 2 according to an embodiment of the present invention is determined by using a predetermined threshold and a weight. The process of correction is performed. In step 407, the black-and-white image produced in step 405 is enlarged and interpolated in a well-known bicubic manner. In step 409, the black-and-white image enlarged and interpolated in step 407 is transmitted by fax through a predetermined network or stored in an internal memory of the mobile terminal.

According to the present invention as described above, in a mobile terminal having a low resolution camera, the read rate of the black and white document image can be improved in the process of converting the color document image photographed by the camera into a black and white document image.

In addition, according to the present invention, it is possible to send a document image photographed using a mobile terminal equipped with a low resolution camera through a communication network by fax.

Claims (4)

A mobile terminal having a digital camera for photographing a subject and a display unit for displaying an image received from the digital camera, A memory for storing luminance and color values of each pixel; Extracting the red, green, and blue color values of each pixel from the color image taken by the digital camera, converting the red, green, and blue color values extracted for each pixel into luminance values and color values, and storing them in the memory; If the converted color value for each pixel is greater than or equal to a threshold value, and if the converted color value is greater than or equal to the threshold value, correct the converted luminance value corresponding to the pixel, and use the corrected luminance value to perform the correction. A control unit for converting the captured color image into a black and white image, Mobile unit for transmitting the converted black and white image to a predetermined communication network. The method of claim 1, And the controller multiplies the luminance value converted corresponding to the corresponding pixel by a predetermined weight less than 1 to correct the luminance value converted corresponding to the corresponding pixel. In the method for converting a color image photographed in a mobile terminal having a digital camera into a black and white image, Extracting a luminance value and a color value for each pixel using red, green, and blue values corresponding to each pixel in the color image; Comparing each color value extracted for each pixel with a predetermined threshold value; Correcting a luminance value of a pixel corresponding to a color value greater than or equal to the threshold value as a result of the comparison; And converting the color image into a black and white image using the corrected luminance value. The method of claim 3, wherein The correction process, And multiplying a luminance value of the corresponding pixel by a predetermined weight less than one.

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