KR101317308B1 - Image processing apparatus and control method the same - Google Patents

Abstract

The present invention relates to an image processing apparatus and a control method thereof, and in particular, the present invention evaluates edge pixels of a black character and, when judged to be the actual edge pixels of the original, sharpens and darkens them, but the original background pixels are blurred. If it is determined that the pixels are detected as edge pixels of the scanned image, these pixels are corrected to their original values and brightened to enhance the black characters, making the actual black characters blacker and the background pixels brighter, thereby increasing the sharpness of the black characters. Increase To this end, the present invention is characterized by distinguishing the black characters from the scanned image, adjusting the print thickness of the separated black characters, and printing the adjusted black characters using only the K color.

Description

Image processing apparatus and control method thereof {IMAGE PROCESSING APPARATUS AND CONTROL METHOD THE SAME}

1 is a control block diagram of an image processing apparatus according to an embodiment of the present invention.

2 is a control flowchart of an image processing apparatus according to an embodiment of the present invention.

FIG. 3 is a control flowchart illustrating a process of enhancing sharpness of edge pixels of black characters in FIG. 2.

4 is a diagram for describing a threshold function of FIG. 3.

5 is a view showing a result of sharpening the edge of the black character in the present invention.

6 is a view showing the result of binarization after sharpening the edge of the black character in the present invention.

[Description of the Reference Numerals]

10: image input unit 20: preprocessing unit

30: black character detection unit 40: black character reinforcement unit

50: post-processing unit 60: image output unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and a control method thereof, and more particularly, to an image processing apparatus and a control method thereof capable of improving reproduction quality by improving sharpness of black characters.

In general, an image processing apparatus converts a document created by an application program to be printed by an user or an image taken by a user using a digital camera into encoded data, and converts the data into a form for viewing by the user. It has a function to print. Examples of image processing apparatuses include printers, scanners, copiers, facsimiles, and the like.

In the image processing apparatus capable of color printing, toners of various colors such as CMYK (Cyan, Magenta, Yellow, blacK) are provided. The color combination of the toner of each color is implemented to print the color sense of the image.

After binarizing the color image, the black pixel can be represented as a combination of C, M, Y, K colors. This causes toner dispersion or noise around the edges upon reproduction. Moreover, using this combination, the quality of reproduction is poor because the resulting color does not appear black and the black level is lower than that of the original.

To this end, U.S. Patent No. 6,756,756 enhances the black image by printing the pixel belonging to the black line image portion in K color. That is, the K channel is enhanced and the C, M, and Y channels are suppressed to increase the black level.

However, when the input image is scanned, the edge pixels of the black character are generally blurred. This means that some of the edge pixels are inherently black edge pixels. Therefore, there is a problem that printed characters and thin lines appear thicker or appear to be printed out at a lower resolution.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an image processing apparatus and a control method thereof capable of improving reproduction quality by improving sharpness of black characters.

The control method of the image processing apparatus of the present invention for achieving the above object comprises the steps of distinguishing the black characters in the scanned image, adjusting the print thickness of the separated black characters, and the black thickness adjusted black characters And printing using only colors.

In addition, another method of controlling an image processing apparatus of the present invention is to distinguish black characters from a scanned image, to distinguish edge pixels of the separated black characters, and to determine maximum and minimum values between pixels. Setting a centered window of pixels, calculating a threshold value based on the maximum and minimum values, and determining whether the pixel of interest is an edge pixel or a background pixel of the original image based on the calculated threshold value. Correcting the pixel of interest according to the edge pixel value if the pixel of interest is an edge pixel, and correcting the pixel of interest to the background pixel value of the pixel of interest; and reflecting the result of the correction; Characterized in that it comprises the step of printing.

In addition, the image processing apparatus of the present invention includes an image input unit for reading an image, a black character detection unit for detecting an edge region of a black character from the read image, and determining whether the edge region is an edge pixel or a background pixel, And a black character reinforcement unit for correcting pixels in the edge area based on the determination.

In addition, another image processing apparatus of the present invention is a black character detection unit for distinguishing the black characters from the scanned image, a black character enhancement unit for controlling the print thickness of the separated black characters, and the printing thickness adjusted black characters K color It characterized in that it comprises an image output unit for printing using only.

In addition, another image processing apparatus of the present invention includes a black character detection unit that distinguishes black characters from a scanned image, and distinguishes an edge pixel of the black characters; Setting a window, calculating a threshold value based on the maximum value and the minimum value, calculating a threshold value based on the maximum value and the minimum value, and according to the calculated threshold value, whether the pixel of interest is an edge pixel of the original image or A black character reinforcement unit for determining whether the pixel of interest is a background pixel, and correcting the pixel of interest to the edge pixel if the pixel of interest is an edge pixel, and correcting the pixel of interest to the background pixel if the pixel of interest is a background pixel; It characterized in that it comprises an image output unit for printing the black character enhanced by the black character enhancement unit using only the K color.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

1 is a control block diagram of an image processing apparatus according to an embodiment of the present invention. 1, an image input unit 10 for reading an image, a preprocessor 20 for preprocessing an image read through the image input unit 10, and an image preprocessed through the preprocessor 20. The black character detection unit 30 for detecting black characters, the black character reinforcement unit 40 for reinforcing the edge pixels of the black characters detected by the black character detection unit 30, and the black character reinforcement unit 40 And a post-processing apparatus 50 for post-processing such that the enhanced black characters are printable, and an image output unit 60 for printing out the post-processed image by the post-processing apparatus 50. The image processing apparatus may be, for example, a host computer that provides black characters or an image forming apparatus that processes and prints black characters. The input unit 10 may be an interface that scans an image from a medium as an input image or receives data as an input image.

The preprocessing unit 20 displays image data displayed as hue, brightness, and saturation components corresponding to each pixel by using the R, G, and B components of the image of the document scanned from the scanner. , That is, get the pixel value.

The black character detection unit 30 uses the pixel value pre-processed by the preprocessing unit 20, preferably brightness data, to draw each pixel of interest into a black character region and a background region, and in the case of a black character region, an edge region of the black character. By classifying as, it is detected whether each pixel of interest is a background pixel or a pixel of a black character.

The black character reinforcement unit 40 finds the maximum and minimum values of the window centered by the edge pixel of the black character with respect to the black character detected by the black character detection unit 30, and threshold for determining the pixel. The black character is enhanced by calculating a value, sharpening an edge pixel, and correcting a background pixel with the original pixel.

2 is a control flowchart of a control method of an image processing apparatus according to an exemplary embodiment of the present invention. 2, in the present invention, an image input step S100, a preprocessing step S110, a black text enhancement step S120 to S140, a post processing step S150, and a printing step S160 are performed. The black character enhancement step (S120 ~ S140) is composed of a black character detection step (S120), black character detection determination step (S130), black character edge sharpening step (S130).

As described above, when the original image is scanned, the pixels of the transition region between the black characters and the background are blurred as shown in FIG. 5A for various reasons. If this is not handled properly, the reproduced black characters may become thicker and blurry compared to the original.

Therefore, in the black character enhancement step (S120 to S140) of the present invention, the pixels of the original image are blurred, but the pixels are detected as the edge pixels of the black characters of the scanned image, thereby brightening the pixels. Darkening the pixels improves the sharpness of black characters. To do this, evaluate the edge pixels of the black character to increase the sharpness and enhance the blackening if the evaluated edge pixels evaluate to the actual edge pixels of the original image, and the original background pixels if the evaluated edge pixels evaluate to the background pixels of the original image. Correct according to the value.

FIG. 3 is a flowchart illustrating a process of enhancing sharpness of edge pixels of a black character in FIG. 2. Referring to FIG. 3, the black character reinforcement unit 40 first sets a window centered by a pixel of interest of a black character (S131), and among the pixel values in the set window, the maximum value Max and the minimum value ( Min) (S132).

The threshold value for determining whether the pixel of interest is an edge pixel or a background pixel in the original image is calculated using the found maximum and minimum values (S133).

Thereafter, the pixel value and the threshold value of interest are compared (S134).

If the result of the comparison is that the pixel value of interest is less than the threshold value, the pixel of interest is determined as an edge pixel of the original image (S135). If it is determined that the edge pixel, the pixel value of the pixel of interest is lowered and blackened (S136).

On the other hand, if the pixel value of interest is a threshold value or more as a result of the comparison, it is determined that the pixel of interest is the background pixel of the original image (S137). If it is determined as the background pixel, the background pixel is corrected by increasing the pixel value of the pixel of interest to whiten (S138).

The above threshold is defined as max- (max-min) * α shown in FIG. 4, where α is an actual value in the range of 0 to 1. This value is called the text thickness variable. By controlling this value of α, the threshold can be made larger or smaller. In other words, more or fewer pixels will be darkened with α.

For example, as α approaches 0, the threshold approaches max, and as α approaches 1, the threshold approaches min. As the threshold approaches max, more pixels will be darker, and fewer pixels will be brighter. This makes the printed output look thicker and blurry. On the other hand, as the threshold approaches min, fewer pixels will darken and more pixels will lighten. The α value depends on the characteristics of the scanner. By controlling α, the thickness of the printed character can be controlled.

Figure 5 shows the result of sharpening the edge of the black character in the present invention, Figure 6 shows the result of binarization after sharpening the edge of the black character in the present invention, Figure 7 is a document printed in the present invention Shows the result of scanning.

As shown in Fig. 5 and Fig. 6, when the threshold value when α is 0.6 is applied, the black character becomes cleaner and thinner than the threshold value when α is 0.5. In addition, the binarization results are intensified. Since black characters are provided by a combination of C, M, Y, and K colors after binarization, the printed black characters may not appear black and there may be some noise around edge pixels, but the black characters in the present invention The edges of are clean and the printed black characters appear perfectly black because only the K color is used instead of the combination of C, M, Y, and K, with the C, M, and Y channels of black character pixels suppressed to 255. In addition, it can reduce unexpected noises around black characters.

As described in detail above, according to the present invention, the edge pixels of the black character are evaluated and sharpened and darkened when judged to be the actual edge pixels of the original, and the background pixels of the original are blurred, but the edge pixels of the scanned image are blurred. If it is determined that the pixels are detected as pixels, the pixels are corrected to their original values and brightened to enhance the black characters, thereby making the actual black characters blacker and the background pixels brighter, thereby increasing the sharpness of the black characters. .

In addition, according to the present invention, by outputting the black characters only in the K color, higher discrimination can be obtained and the noise of the black characters can be reduced during reproduction.

Claims (19)

Distinguishing black characters from the scanned image; Distinguishing edge pixels of the separated black characters; Setting a window in which the pixel of interest of the black character is centered to determine a maximum value and a minimum value of brightness values between pixels; Calculating a threshold value based on the maximum and minimum values; Adjusting the print thickness of the separated black characters according to the threshold value; And printing the black character whose print thickness is adjusted using only the K color. The method of claim 1, Comparing the calculated threshold value with the brightness value of the pixel of interest, if the brightness value of the pixel of interest is less than the threshold, the pixel of interest is determined as an edge pixel of the original image, and the brightness value of the pixel of interest is the threshold value. And determining the target pixel as the background pixel of the original image. 3. The method of claim 2, Correcting the attention pixel in a direction to emphasize black if the attention pixel of the separated black character is an edge pixel of the original image; and if the attention pixel is the background pixel of the original image, white the attention pixel. And correcting in the direction of emphasis. delete The method of claim 1, And reducing the thickness of the black characters as the threshold is closer to the minimum value, and increasing the thickness of the black characters as the threshold is closer to the maximum value. Way. The method of claim 1, And the threshold value is a value smaller than an average value of the maximum value and the minimum value. Distinguishing black characters from the scanned image; Distinguishing edge pixels of the separated black characters; Setting a window in which the pixel of interest is centered to determine a maximum value and a minimum value between the pixels; Calculating a threshold value based on the maximum and minimum values; Determining whether the pixel of interest is an edge pixel or a background pixel of an original image based on the calculated threshold value; Correcting the pixel of interest in the direction of highlighting black if the pixel of interest is an edge pixel, and correcting the direction of white in the direction of highlighting white of the pixel of interest; And printing the black characters using only the K color by reflecting the correction result. The method of claim 7, wherein And the threshold value is calculated to be smaller than an average value of the maximum value and the minimum value. delete An image input unit for reading an image; A black text detector detecting an edge region of the black text from the read image; Distinguishes the edge pixels of the black character, sets a window in which the pixel of interest is centered to determine a maximum value and a minimum value between the pixels, calculates a threshold value based on the maximum value and the minimum value, and calculates a threshold value based on the calculated threshold value. And a black text reinforcement unit configured to determine whether the pixel of interest is an edge pixel or a background pixel of the original image, and to adjust the print thickness by correcting the pixel in the edge area based on the determination. The method of claim 10, And a processing unit for obtaining a pixel value of the black character. 12. The method of claim 11, And the black character detecting unit classifies the black character into a black character area, a background area, and an edge area based on the pixel value obtained by the processing unit. The method of claim 12, And the pixels of the edge region are darkened or lightened according to the pixels of the black character region or the background region based on the determination by the black character enhancer. 12. The method of claim 11, And said threshold value is variably controlled by a change in character thickness. The method of claim 10, And an image output unit which outputs the enhanced image corrected by the black character reinforcement unit. The method of claim 10, And a preprocessing unit for obtaining image data represented by hue, brightness, and saturation corresponding to the pixel value of the black character. The method of claim 10, And a post-processing section for processing the black text enhanced by the black text enhancement section to print the enhanced black text. delete A black character detection unit to distinguish black characters from the scanned image and to distinguish edge pixels of the black characters; Setting a window in which the pixel of interest is centered to determine the maximum and minimum values between the pixels, calculating a threshold based on the maximum and minimum values, calculating a threshold based on the maximum and minimum values, and calculating the Determine whether the attention pixel is an edge pixel or a background pixel of the original image according to the determined threshold value, if the attention pixel is an edge pixel, correct the attention pixel according to the edge pixel, and if the attention pixel is a background pixel, the attention Black character reinforcement unit for correcting the pixel to match the background pixel; And an image output unit for printing the black characters enhanced by the black character enhancement unit using only K colors.

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