JPH0345085A - Sharpness emphasis method for television picture - Google Patents

Abstract

PURPOSE:To generate a hard copy with excellent picture quality by applying sharpness emphasis based on a component keeping edge component of a picture best among R, G, B color components in a television picture. CONSTITUTION:As to R, G, B color components in a noted picture element S(m,n) in a television picture stored in a frame memory 14, unsharp signals UR, UG, UB are obtained. Then the unsharp signals UR, UG, UB of each color component are subtracted from the color components of the noted picture element to generate edge signals ER, EG, EB. Then among the edge signals ER, EG, EB obtained from each color component ef R, G, B, an edge signal with the largest absolute value is selected and added to primary picture information of each color component corresponding to them. Thus, the sharpness is emphasized based on the signal keeping the edge component of the picture best. Thus, the sufficient sharpness emphasis effect is obtained.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for enhancing sharpness of a television image, and in particular, sharpness enhancement processing in video printing for creating hard copies of films, printed matter, etc. from television images. Regarding.

<Prior Art> It is well known that the image quality of printed matter is greatly influenced by the suitability of sharpness enhancement in the plate-making process. In general photolithography processes for printing, sharpness enhancement is generally performed as follows.

Red (R) and green (
An unsharp (blur) signal is created based on the R component or G component (hereinafter referred to as emphasis color component), which has a relatively large effect on sharpness among the color components of G) and blue (B), Sharpness is emphasized by subtracting this unsharp signal from the original image signal of the emphasized color component to create an edge signal of that color component, and adding this edge signal to the original image signal of the emphasized color component. ing.

Sharpness enhancement processing is equally important in video printing devices that create hard copies from television images; for example, as described in Japanese Patent Publication No. 63-22674,
A video image plate making apparatus disclosed in Japanese Patent Publication No. 63-22718 also describes a component that performs sharpness enhancement processing. However, since these publications do not disclose a specific method of sharpness enhancement processing, it is considered that processing similar to the sharpness enhancement processing used in the photolithography process described above is performed.

<Problems to be Solved by the Invention> However, if the conventional sharpness enhancement processing as described above is directly applied to video printing, the following problems arise.

As is well known, in the NTSC television system, R
, G, B image signals are not transmitted as they are, but are processed into a luminance signal (Y) and two color signals (1, Q) in a matrix circuit.
) before being transmitted. Here, the bandwidth of each signal is set to 4MHz for the luminance signal Y, and
The signal is 1.5! vl.

The Q signal is 0.5 MHz, and the color signal 1. Q
The bandwidth of the luminance signal Y is narrower than that of the luminance signal Y.

Therefore, the Journal of the Television Society (Vol. Nα519)
86 P25), for example, red with 100% saturation is 3 times smaller than a white signal at IMHz.
The response is only 0%, which means that the resolution of the high chroma portion of the original image is low and the sense of sharpness is also lost. When creating a hard copy from such a television image, even if you create an unsharp signal from the red signal component and create an edge signal by taking the difference between this unsharp signal and the original image information, the red There is a problem in that a sufficient sharpness enhancement effect cannot be obtained in areas with high chroma because there are few edge components.

Furthermore, in order to prevent interline flicker caused by interlaced scanning, the television camera itself is not provided with very high resolution, which is one of the reasons why it is difficult to emphasize the sharpness of television images.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for enhancing the sharpness of a televised image, which can obtain a sufficient sharpness enhancement effect.

Means for Solving the Problems> In order to achieve the above objects, the present invention has the following configuration.

That is, the present invention is a method for emphasizing the sharpness of a television image in video printing for creating a hard copy from a television image, in which red (R), green (G), blue ( Create an unsharp signal for each color component in B), subtract the unsharp signal for each color component from the original image information for each corresponding color component to create an edge signal for each color component, and The edge signal having the maximum absolute value is selected from among the edge signals, and the maximum edge signal is added to the original image information of each corresponding color component.

<Operation> According to the present invention, among the edge signals obtained from each color component of R, G, and B, the edge signal with the largest absolute value is selected, and this is used as the original image information of each corresponding color component. Since the edge components of the image are added, sharpness is enhanced based on the signal that best retains the edge components of the image.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a video printing apparatus using a sharpness enhancement method according to an embodiment of the present invention.

NT recorded on video tape recorder (VTR) 11
SC television image signal is R, G, B decoder 1
2 and decoded into R (red), G (green), and B (blue) image signals. Each R9G, B image signal is A/
After being converted into digital signals by the D converter 13,
It is applied to the frame memory 14. Frame memory 14
has a storage capacity sufficient to individually store one frame's worth of R, G, and B image signals.

A part of the television image signal output from the VTRII is given to the synchronization signal separation circuit 15, which separates horizontal and vertical synchronization signals and color subcarriers from the image signal. The color subcarrier and the color subcarrier are applied to a clock pulse generation circuit 16, and a timing clock having a frequency four times that of the color subcarrier (3.58 MHz) and an addressing signal for the frame memory 14 are created. The A/D converter 13 divides the section of one scanning line into approximately 910 pixels according to this timing clock, divides the level of the R, G, and B image signals of each pixel into 256 gradations, and outputs the divided pixels. .

The CPU 17 has a function of performing image processing such as sharpness enhancement processing, which will be described later, according to a predetermined program.
It is connected to the buffer memory 22, the console 18, and the emphasis coefficient storage table 21.

When the CPU 17 performs image processing on the image information stored in the frame memory 14, the frame memory 14 is addressed by the CPU 17, but when writing or reading other image signals, the clock pulse generation circuit 16 This is done based on the addressing from.

The R, G, and B image signals output from the A/D converter 13 are sequentially written into the frame memory 14 according to the address designation from the clock pulse generation circuit 16.

At the same time as data is written to the frame memory 14, these data are read from the frame memory 14 and D
After being converted into an analog signal by the /A converter 19, it is output to the monitor television 20. In this way, VTRII
The television image recorded on the monitor TV 20
are displayed in order.

The operator selects an image for which a hard copy is to be created while viewing television images continuously displayed on the monitor television 20. When a desired image is selected via the operation console 18, the CPU 17 selects the frame memory 14.
, the image signal at that time is frozen (fixed).

The CPU 17 stores the frozen 1 in the frame memory 14.
The following description will be made with reference to the flowchart shown in FIG. 2 and FIG. 3, in which the following sharpness enhancement processing is performed on a television image signal for one frame.

In step S1, an unsharp signal Uw,
Find Us and IJ*. Specifically, as shown in FIG. 3, unsharp signals U++, Ua, and Us are obtained by taking the average value of each color component for the pixel of interest S (m, n) and the surrounding eight pixels adjacent to it. can be created. That is, the unsharp signal (J++
, Us , Us are the following formulas ■, ■.

Calculated by ■.

Next, the process advances to step S2, where unsharp signals U,, U, of each color component obtained in step S1 are obtained.

By subtracting U from each color component of the pixel of interest, edge signals E*, Ee, and Em for each color component are created. These edge signals E, , E, , E are calculated using the following equations (2), (2), and (2).

E++ = R(m, n) U++ --
■Ee -G (m, n) -UG -■E
m = B (m, n) Us' −−■
When the edge signal of each color component is determined, the process proceeds to step S3, and the edge signal having the maximum absolute value is selected from among the edge signals E*, Ec, and Ei of each color component. Hereinafter, this edge signal will be referred to as the maximum edge signal, and E
Indicated by MAX.

When the maximum edge signal E NAX is selected, step S
4 and S5 are performed.

First, in step S4, the pixel of interest S
Calculate the saturation Sat(m, n) of (m, n).

5at(a+,n)=l R(m,n)−G(m,
n) + l G (m, n) - B (m, n) 10 l
B (m, n) - R (m, n)...■ Then, in step S5, with reference to the emphasis coefficient storage table 21, the calculated saturation Sat of the pixel of interest is calculated.
Determine an emphasis coefficient K according to (m, n).

The enhancement coefficient storage table 21 stores in advance enhancement coefficients corresponding to the saturation so that the enhancement coefficient increases as the saturation of the pixel of interest increases.

When the emphasis coefficient K is determined, the process proceeds to step S6, and the following equation
As shown in [Phase], each color component R whose sharpness is emphasized by adding the value obtained by multiplying the maximum edge signal E) TAX by the emphasis coefficient K to each color component of the pixel of interest S(m, n) ' (m, n)G' (m, n), B'
Find (m, n).

R' (m, n) = R (a+, n) -E+iy+
-・=■G' (m, n) -G(s+n)+
-Emhx -=・■B' (m, n)
=B(m,n)+K-EMAX--0 After sharpness enhancement processing is performed on each color component of the pixel of interest S (m, n) as described above, step S7
In step S8, it is determined whether the processing has been completed for all pixels of the television image stored in the frame memory 14. If the processing has not been completed, the process advances to step S8, and the next pixel in the horizontal scanning direction is selected as the pixel of interest. and step S1
Return to and repeat the process described above.

Regarding one frame of the television image stored in the frame memory 14, the sharpness enhancement processing described above,
When pixel interpolation processing is performed as necessary, the image-processed R, G, and B image signals are stored in the buffer memory 2.
2 and an interface 23 to a color scanner 24 for plate making as an output device. The color scanner 24 converts these R, G, and B image signals into Y(
Yellow) 1M (magenta), C (cyan), and K (black) are converted into color signals to create respective color separation plates.

As described above, according to the sharpness enhancement method for television images according to the present embodiment, edge enhancement is performed based on the component that best retains the edge component among the R, G, and B color components. Since the enhancement coefficient is changed according to the saturation of the pixel of interest, a sufficient sharpness enhancement effect can be obtained.

Note that in the above-described embodiment, the emphasis coefficient was changed according to the saturation of the pixel of interest, but sharpness emphasis processing may be performed using a constant emphasis coefficient set in advance.

<Effects of the Invention> As is clear from the above description, according to the present invention, among the R, G, and B color components of a television image, the color component that best retains the edge component of the image is selected. Sharpness enhancement is applied, so you can obtain a sufficient sharpness enhancement effect even in high-chroma areas of the image.
Therefore, it is possible to create a hard copy with good image quality that compensates for the low resolution of the television image.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a video printing apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart showing a procedure for sharpness enhancement processing in the video printing apparatus according to an embodiment, and FIG. 3 is a sharpness FIG. 2 is an explanatory diagram of a pixel of interest and surrounding pixels to be subjected to emphasis processing. 1l-VTR1:”・R, G, B decoder 13...A
/D converter 14...Frame memory 15...Synchronization signal separation circuit 16...Clock pulse generation circuit 17...CPU 18...Operation console 19.
...D/A converter 20...Monitor TV 21...
Emphasis coefficient storage table 22...Buffer memory 23...Interface 24...Color scanner

Claims (1)

[Claims] (1) A method for emphasizing the sharpness of a television image in video printing where a hard copy is created from a television image. Create an unsharp signal for each color component, subtract the unsharp signal of each color component from the original image information of each corresponding color component to create an edge signal for each color component, and calculate the edge signal of each color component. A method for enhancing the sharpness of a television image, comprising: selecting an edge signal whose absolute value is the largest among them, and adding the largest edge signal to original image information of each corresponding color component.