KR100520625B1 - Method for displaying picture using histogram equalization in wireless terminal - Google Patents

Abstract

 A method of displaying a photographic image of a mobile terminal, the method comprising: determining brightness of pixels of a selected photographic image, accumulating pixels corresponding to the determined brightness in the determined brightness, and calculating the frequency of the brightness; Obtaining a scale histogram value using the scaled image and normalizing the calculated value; mapping the normalized value to positions of pixels corresponding to the selected photo image; and displaying a photo image mapped to the normalized value Is done.

Description

TECHNICAL FOR DISPLAYING PICTURE USING HISTOGRAM EQUALIZATION IN WIRELESS TERMINAL}

The present invention relates to a method of processing a video screen, and more particularly, to a method capable of displaying a photographic image by processing it as a clear photographic image.

Currently, portable mobile communication terminals are converting to a structure capable of transmitting high speed data in addition to voice communication functions. Data that can be processed by the mobile terminal performing the data communication may be packet data and image data.

Currently, the mobile terminal has a function of transmitting and receiving image data. Therefore, the video screen received from the base station is stored or the acquired video screen is transmitted to the base station. In addition, the portable terminal may include a camera for photographing an image screen and a display unit for displaying an image signal photographed by the camera. The camera may use a CCD or a CMOS sensor, and the display unit may use an LCD. In addition, with the miniaturization of the camera device, the device for capturing the image is becoming more and more miniaturized. The portable terminal may capture a video screen and display the moving picture and the still picture, and transmit the captured video screen to the base station.

As described above, as the needs of operators and consumers are increased with respect to video mails, the above-mentioned services are implemented, and the trend is to be greatly increased in the future. In addition, the functions of editing a video screen by a user's operation in the portable terminal are also increasing. For example, technologies for adjusting (zoom in, zoom out) or synthesizing a plurality of photographic images stored in a portable terminal are implemented.

Accordingly, an object of the present invention is to provide a method for displaying a clear picture by uniformly processing the distribution of contrast values in a picture image in a mobile terminal.

Another object of the present invention is to provide a method for smoothing a histogram by normalizing a photographic image in a mobile terminal, and mapping the normalized value into an image to display a clear photographic image.

In the method for displaying a photo image of a mobile terminal according to an embodiment of the present invention for achieving the above object, determining the brightness of the pixels of the selected photo image, by accumulating the pixels corresponding to the determined brightness in the determined brightness Calculating a frequency number of the brightness, obtaining a scale histogram value using the frequency, normalizing the normalized value, and mapping the normalized value to positions of pixels corresponding to the selected photographic image; And displaying a photo image mapped to the normalization value.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that the same components in the figures represent the same numerals wherever possible.

In the following description, details such as brightness values of the original image and result values of the normalized image for making a clear picture are shown to provide a more general understanding of the present invention. It will be apparent to one of ordinary skill in the art that the present invention may be readily practiced without these specific details and also by their modifications.

1 is a diagram showing the configuration of a mobile terminal according to an embodiment of the present invention, which may be a configuration of a mobile telephone.

Referring to FIG. 1, the RF unit 23 performs a wireless communication function of the portable telephone. The RF unit 23 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 20 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 20 may be configured of a modem and a codec CODDEC. The codec includes a data codec for processing data and an audio codec for processing an audio signal such as voice. The audio processor 25 plays a function of reproducing a received audio signal output from the audio codec of the data processor 20 or transmitting a transmission audio signal generated from a microphone to the audio codec of the data processor 20.

The key input unit 27 includes keys for inputting numeric and character information and function keys for setting various functions. In addition, the key input unit 27 may include function keys for executing a photo image synthesis and album preview function according to an embodiment of the present invention.

The memory 30 may include program memory and data memories. The program memory may store programs for controlling a general operation of the portable telephone and programs for processing an image signal applied to a display unit in an embodiment of the present invention. The data memory also stores a data generated during the execution of the programs.

The controller 10 performs a function of controlling the overall operation of the portable terminal. In addition, the controller 10 may include the data processor 20. In addition, the controller 10 controls operations of making a clear picture by uniformly processing brightness values of the selected picture image according to a mode command set from the key input unit 27 according to an embodiment of the present invention.

The camera module 40 includes a camera sensor for capturing image data, converting the photographed optical signal into an electrical signal, and a signal processor for converting the analog image signal photographed from the camera sensor into digital data. Herein, it is assumed that the camera sensor is a CCD sensor, and the signal processor may be implemented by a digital signal processor (DSP). In addition, the camera sensor and the signal processor may be integrally implemented or may be separately implemented.

The image processor 50 performs a function of generating screen data for displaying an image signal output from the camera unit 40. The image processor 50 processes the image signal output from the camera unit 40 in units of frames, and outputs the frame image data according to the characteristics and size of the display unit 60. In addition, the image processor 50 includes an image codec and performs a function of compressing the frame image data displayed on the display unit 60 in a set manner or restoring the compressed frame image data to the original frame image data.

The display unit 60 displays a frame image signal output from the image processor 50 on a screen, and displays user data output from the controller 10. In addition, the display unit 60 displays a video signal reproduced under the control of the controller 10. The display unit 60 may use an LCD. In this case, the display unit 60 may include an LCD controller, a memory capable of storing image data, and an LCD display device. In this case, when the LCD is implemented using a touch screen method, the LCD may operate as an input unit.

The communication interface 70 is connected to an external communication device and performs a function of communicating a picture image with a portable terminal. Wherein the external communication device is a scanner, a computer. Digital cameras and the like. The communication interface 70 may perform a communication interface function with the external communication devices under the control of the controller 10 to output a stored picture image or to receive a picture image.

Referring to FIG. 1, the mobile phone according to an embodiment of the present invention may perform an operation of displaying or transmitting a person or a surrounding environment on a video screen. First, the camera unit 40 may be mounted on a portable telephone or connected to a predetermined position outside. That is, the camera unit 40 may be an external camera or an internal camera. The camera unit 40 may use a charge coupled device (CCD) sensor. The image captured by the camera unit 40 is converted into an electrical signal by an internal CCD sensor, and then the signal processor converts the image signal into digital image data. The converted digital image signal and the synchronization signal are output to the image processor 50. The synchronization signal may be a horizontal synchronization signal (Hsync) and a vertical synchronization signal (Vsync).

2 is a diagram illustrating an example of a configuration of the image processor 50 according to an embodiment of the present invention.

Referring to FIG. 2, the camera interface 211 interfaces the image data and the synchronization signals HREF and VREF from the camera unit 40. The HREF is a horizontal validity period flag, which is used as a line synchronization signal. The HREF may be a horizontal synchronous signal for reading image data stored in a line memory in the camera unit 40 on a line basis. The VREF is used as a frame synchronization signal as a vertical validity period flag. The VERF is used as a signal that can be transmitted by the signal processor 60 which processes image data photographed by the camera unit 40. The VREF is generated in units of one frame and may be a vertical synchronization signal.

The LCD interface 217 may access the image data of the controller 10 and the display screen generator by switching the selector 219.

The scaler 213 performs a function of scaling the magnitude of the image signal photographed by the camera unit 40 to the magnitude of the image signal that can be displayed on the display unit 60. That is, the number of pixels of the video signal of one frame photographed by the camera unit 40 and the number of pixels of the one frame video signal that can be displayed on the display unit 60 are different. The scaler 213 reduces (decimates) the number of pixels of one frame photographed by the camera unit 40 to the number of pixels of one frame that can be displayed on the display unit 60 or sets an appropriate number of pixels of the photographed one frame. To display on the display unit.

The image codec 231 compresses the captured image signal or restores the compressed image signal to the original image signal. In an embodiment of the present invention, the image codec 231 is assumed to be a JPEG codec. The image codec 80 performs JPEG compression on the image data output from the camera unit 40 and outputs the encoded data to the control unit 10 or restores the compressed coded data input from the control unit 10 to the scaler 213. Perform.

The small screen processing unit 221 reconstructs the image data output from the image processing unit to the set small screen. The small screen processing unit 221 cuts the left and right ends and the top and bottom ends of the video screen displayed on the display unit 60 to a predetermined size, and then decimates the pixels of the cut video screen to generate a small screen.

The control interface 221 performs an interface function between the image processor 50 and the controller 10, and also performs an interface function between the display unit 60 and the controller 10. That is, the control interface 221 performs an interface function between the controller 10 and the image processor 50. The control interface 221 is a common interface for accessing the image processor 50 and the display unit 60 through the image processor 50.

The selector 219 selects data output from the image processor 50 or data output from the controller 10 according to the control signal output from the controller 10 and outputs the data to the display unit 60. Here, the first control signal refers to a signal for activating a bus between the image processor 50 and the display 60, and the second control signal is a signal to activate a path between the controller 10 and the display 60. In addition, the controller 10 may perform the bidirectional communication between the display unit 60 through the selector 219.

Accordingly, the portable terminal having the configuration as shown in FIGS. 1 and 2 may receive a video screen obtained from the camera 40, the RF unit 23, the communication interface unit 70, and the like and store the picture image in the memory 30 as a picture image. They may be stored as a small screen through the small screen processor 241 of the image processor 50. At this time, the photographed images may be images as shown in FIG. 5A.

In the photographic image of FIG. 5A, light and dark points are distributed. At this time, the distribution of the contrast value may be biased or uneven to one side. Therefore, the uniform distribution of the contrast values improves the overall contrast balance. In this way, the processed picture image becomes dark and the too bright part becomes dark to maintain the appropriate brightness value, thereby displaying the picture image clearly.

In order to sharpen the image as described above, high pass filtering typically requires histogram equalization in the form of post-processing to form a suitable image. Since the high frequency filter is not used alone for the improvement of the image, it is difficult to see the improvement effect of the image. Therefore, in the embodiment of the present invention, it is assumed that a sharp photographic image is made by using histogram smoothing, which can see an improvement effect of the image, rather than applying a high-pass filter to the image.

In the embodiment of the present invention, the normalization process for making a clear picture is simplified, and histogram smoothing is performed in four steps as follows. First, the brightness of each pixel of the selected video screen is determined. In the second step, the frequency of brightness values using the histogram is calculated according to the determined brightness. In the third step, the accumulated histogram value is obtained using the frequency and the normalized value. In the fourth step, the normalized accumulation histogram is used as a grayscale matter function to map gray level values. In this case, the normalization means that the value converted by the conversion function exceeds the range to be converted, and adjusts the excess values to be remapped within a desired range.

4A to 4D, in order to make a clear picture, the first step is to determine the brightness of each pixel of the selected picture image. In the embodiment of the present invention, it is assumed that the brightness of the selected photo image has the brightness value as shown in FIG. 4A.

Subsequently, in a second step, when the brightness of each pixel determined as shown in FIG. 4A is checked to obtain a frequency of brightness values of the selected photographic image, this is as shown in FIG. 4B. 4B is an accumulation histogram of a photographic image having the same brightness as that of FIG. 4A. Referring to FIG. 4B, the brightness "0" is one, the brightness "1" is two, the brightness "2" is two, the brightness "3" is six, and the brightness "4" is five. have.

Secondly, the accumulation histogram as described above is smoothed. The histogram smoothing is implemented by accumulating a normalized accumulation histogram and then using gray scale mapping using Equation 1 below. The smoothing of the accumulated histogram obtained as described above is performed by Equation 1 below.

In Equation 1, n _i is the total number of pixels of the photographic image.

g _max is the maximum value of brightness

                     H (i) is the cumulative histogram

k _i is the normalized value (converted image pixel value)

When the accumulated histogram as shown in FIG. 4B is normalized to Equation 1, it is as shown in FIG. 4C, which is shown in Table 1 below.

brightness Accumulated Histogram Color accumulation (sum) Normalized value 0 One One 0.43 One 2 3 1.31 2 2 5 2.18 3 6 11 4.81 4 5 16 7.00 5 0 16 7.00 6 0 16 7.00 7 0 16 7.00

Thereafter, in the third step, the normalized values are mapped to brightness values of the selected photographic image as shown in FIG. 4A to generate a smoothed photographic image by an accumulation histogram. At this time, the photographic image as shown in FIG. 4A is normalized as shown in FIG. 4D, and the normalized photographic image is displayed as a clear photographic image.

3 is a flowchart illustrating a procedure of making a selected photographic image into a clear photographic image using an accumulation histogram according to an embodiment of the present invention.

Referring to FIG. 3, when the user of the mobile terminal selects a clear picture function after selecting a picture image, the controller 10 detects it in step 311 and initializes x, y variables of the selected picture image in step 313. Herein, the x variable means the x coordinate value of the selected pixel and the y variable means the y coordinate of the selected pixel.

In step 315, the control unit 10 reads the pixels of the current x and y coordinates to determine the brightness value, and in step 317 updates the accumulation histogram according to the determined brightness value. In operation 319, the controller determines whether the current pixel is the last pixel of the corresponding line. In operation 321, the next pixel of the current pixel is designated. If the update of the accumulation histogram for the last pixel of the line is completed while repeating the above operation, the process proceeds to step 323 to check whether the current pixel is the last pixel of the last line. If it is not the last line, the process proceeds to step 325 where the x variable is initialized to 0 and the y variable is increased by 1 to designate the first pixel of the next line, and then proceed to step 315. The above operation is repeated until the accumulation histogram of the last pixel of the last line is made.

In operation 315 and operation 325, the brightness value is determined in each of the pixels of the selected photographic image as illustrated in FIG. 4A, and an accumulation histogram as illustrated in FIG. 4B is created according to the determined brightness value.

When the accumulation histogram as shown in FIG. 4B is made, the number of pixels according to each brightness value is added. To this end, the controller 10 initializes the i variable to 0 in step 327. At this time, the i variable is a variable representing the brightness value, and in the exemplary embodiment of the present invention, it is assumed that the i variable is the brightness according to the gray level from 0 to 255. Thus, the last value of i is 255. In step 329, the controller 10 accumulates the color values corresponding to the i variables. That is, the controller 10 stores the number of pixels corresponding to the brightness corresponding to the i variable in the accumulated histogram as shown in FIG. 4B in the number of pixels accumulated up to now. After the color accumulation is completed, the control unit 10 proceeds to step 333 if i is not the last brightness value, specifies the next brightness value, and repeats step 329. If i is the last brightness value, the color accumulation operation is performed. To exit. The color accumulation as described above becomes the color sum value of Table 1. That is, in steps 327 to 333, the brightness histogram is sequentially assigned to each brightness value, and the accumulated number of pixels according to the corresponding brightness value is accumulated.

Thereafter, the controller 10 performs an operation of normalizing using a cumulative value of the number of pixels according to the brightness value. In this case, the normalization is performed using Equation 1. To this end, the controller 10 initializes the i value in step 335, and then normalizes the brightness of the specified i using Equation 1 in step 337. After that, if the i is not the last brightness value, the controller 10 proceeds to step 341, specifies the next brightness value, and repeats step 337. If i is the last brightness value, the control unit ends the normalization operation. When the above operation is performed, normalization of each brightness value is completed. At this time, when the normalization is completed, a normalization value according to each brightness is created as shown in FIG. 4C.

In step 343, the controller 10 creates a normalization table for pixel brightness values of the photographic images. In this case, the normalization table may be made as shown in Table 1. Here, the decimal point may be rounded to form the normalization table. In step 345, the controller 10 maps the brightness values of the normalized table to the photo image of FIG. 4A to create a photo image of FIG. 4D. In this case, the photographic image as shown in FIG. 4D uniformly distributes the intensity values of the pixels. The photographic image data mapped to the normalization value is transmitted to the display unit 60 in step 347 for display.

As described above, in the mobile terminal storing the photo image, the contrast value of each pixel of the selected photo image is made uniform by the user, thereby improving contrast balance of the displayed screen image. In the image, the dark image becomes bright and the too bright image is slightly dark, so that the appropriate brightness value can be maintained, so that the sharp image can be displayed. In addition, since the data processed as the clear picture image can be stored in an external device through a communication interface or transmitted to a base station and transmitted to other subscribers, the display function of the terminal can be improved.

1 is a diagram illustrating a configuration of a portable terminal displaying a video screen according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of an image processing unit in FIG. 1.

3 is a diagram illustrating a procedure of synthesizing an image screen and a background screen according to an embodiment of the present invention.

4A to 4D are diagrams for explaining three stages of histogram smoothing according to an embodiment of the present invention.

5A and 5B show an original photographic image and a processed clear photographic image according to an embodiment of the present invention;

Claims (3)

In the method for displaying a photographic image of a mobile terminal, Determining brightness of the pixels of the selected photo image, accumulating pixels corresponding to the determined brightness in the determined brightness, and calculating a frequency of the brightness; Calculating a normalized value by obtaining a scale histogram value using the frequency and normalizing it; Mapping the normalization value to positions of pixels corresponding to the selected photographic image; And displaying a photographic image mapped to the normalization value. The method of claim 1, wherein the calculating of the normalization value is performed by Equation 1 below. [Equation 1] In Equation 1, n _i is the total number of pixels of the photographic image. g _max is the maximum value of brightness                      H (i) is the cumulative histogram k _i is the normalized value (converted image pixel value) The method of claim 1, wherein the brightness value is a gray level between 0 and 225.