JPH0738221B2 - Color image quality improvement device - Google Patents

Description

The present invention relates to an apparatus for improving the quality of an image created by a computer, such as computer graphics and CAD.

[Outline of Invention]

According to the present invention, filtering is applied only to a boundary between a computer-generated image and its background image and a portion in the vicinity thereof, so as to reduce a so-called jaggedness occurring at the boundary portion when the image is displayed on a raster scan type display device. However, since it does not perform filtering on the entire image, it has a feature that deterioration of image quality can be minimized.

[Conventional technology]

In computer graphics and CAD, various figures (two-dimensional and three-dimensional) are calculated by computer calculation.
It is often created on a three-dimensional image memory and displayed on a raster scan type display device.

FIG. 2 shows a spherical image (1) created by computer calculation, which is superimposed on a background image (2) and displayed on a raster scan CRT display. As shown in FIG. 2, since the spherical image (1) is obtained by calculation, the boundary (3) between the background image (2) and the spherical image (1) is stored in the image memory. So-called jaggedness occurs in units of pixels.

In this way, in general, the boundary of the digital figure created by calculation has a crevice in the unit of the pixel of the image memory, but this crease impairs the reality of the figure, and the man-machine of computer graphics and CAD. Not convenient for the interface.

Conventionally, in the case of removing such a crease, a signal in the entire image is passed through a spatial filter to blur the crease at the boundary portion.

[Problems to be solved by the invention]

When filtering the entire image as in the past, not only the jagged edges but also the created image part,
Further, the background image is also blurred and the image quality is deteriorated.

[Means for solving problems]

FIG. 1 is a block diagram showing an outline of an example of the device of the present invention.

In the figure, (10) is an image memory as an input image generating means, (20) is a discrimination circuit for discriminating between the background and the created figure, and (30) is a boundary for detecting the boundary between the background and the created figure and the vicinity thereof. A detection circuit, (40) is a background image composing circuit for composing a background image, and (50) is a filter.

[Action]

Image data created by computer calculation from the input terminal (61) is written in the image memory (10), and specific color data from the input terminal (62) is written in the background portion of this image. As this specific color, a color that does not appear as an input image from the input terminal (61) is used.

Therefore, one screen of data in which the background (2) of the spherical image (1) created as shown in FIG. 2, for example, is filled with a specific color is written in the image memory (10).

The data read from the image memory (10) is supplied to the discrimination circuit (20), and the data portion of the specific color is discriminated as the background, and the others are discriminated as the created figure.

The data read from the image memory (10) is also supplied to the background image synthesizing circuit (40), and the determining circuit (20).
Is supplied to the background image synthesizing circuit (40), and the background portion filled with the specific color is replaced with the background image data from the input terminal (63).

The discrimination output from the discrimination circuit (20) is also supplied to the boundary detection circuit (30), and the boundary between the background portion and the created figure and its vicinity are detected by pattern matching.

Then, the composite data from the background image composition circuit (10) is supplied to the filter (50) and the boundary detection circuit (30).
The boundary information indicating the boundary and the boundary vicinity position is supplied to the filter (50), and the sum of products in the horizontal direction and the vertical direction is applied to the data of only the boundary between the background and the created figure and the vicinity of the boundary in the composite data. The filtering process by the calculation is performed, and the image data in which the jaggedness near the boundary is reduced is obtained at the output terminal (64).

The background image compositing circuit (40) may not be provided if the background portion may remain in the specific color.

〔Example〕

FIG. 3 shows an embodiment of the device of the present invention, which is an example in the case where the example of FIG. 1 is more specifically configured.

The image memory (10) comprises field memories (11) (12) and switch circuits (13) (14) (15), and these switch circuits (13) (14) (15) are input terminals (16).
A field switching signal SW is used to switch each field, and the operation of writing data in one field memory and reading the data from the other field memory is alternately repeated field by field.

The switch circuit (13) is a write data changeover switch,
The computer generated graphic data DA from the input terminal (61) and the specific color data PC from the input terminal (62) are connected to two field memories (11) and (12) via the switch circuit (13). ) And are supplied alternately. That is,
The graphic data DA is written in one of the field memories, and the specific color data PC is written in the other field memory. As this specific color, a color that does not appear in the image data DA, for example, a specific color when the brightness is saturated is selected.

The switch circuit (14) is an address changeover switch, and the field memory to which the graphic data DA is supplied as write data is supplied with the random address data RMAD conforming to the shape of the graphic from the input terminal (18), and the specific color. The sequential address data SQAD from the input terminal (17) is supplied to the field memory to which the data PC of is supplied as the write data.

The switch circuit (15) is a read data changeover switch,
Data is read from the field memory in which the specific color is written prior to the data writing by the sequential address data.

For example, when the data of a specific color is written in the field memory (11) along with the address data SQAD in the previous 1 field, the graphic data DA is written in the next field.
Are written in the field memory (11) along with the random address data RMAD. That is, only the address of the graphic portion is rewritten from the specific color data PC to the graphic data DA. Therefore, at this time, the field memory (1
In 1), the image data that the figure created by the computer and its background are painted in a specific color is written. And when it comes to the next field,
Sequential address data SQAD is supplied to the field memory (11), the image data is read out sequentially, and then the data of the specific color is written to the addresses.

Hereinafter, the above operation will be repeated. The other field memory (12) performs exactly the same operation as described above with a shift of one field.

In this way, the switch circuit (15) obtains the image data DI of the figure in which the background is painted in the specific color, and this is supplied to the discrimination circuit (20).

The discrimination circuit (20) is composed of a comparison circuit (21), and compares the image data DI with the data PC of a specific color from the input terminal (22). When the two match, the background portion, and when they do not match, the figure For example, the discrimination output ID is “0” in the background portion and “1” in the image portion.

The background image synthesizing circuit (40) is composed of a multiplexer (41), and the background image data DB is connected to one input terminal A of the multiplexer.
Image data DI is supplied to the other input terminal B. Then, the discrimination output from the comparison circuit (21) is output to the select terminal.
Image data of input terminal B in the figure part when ID is supplied.
DI is the background image data DB of the input terminal A in the background part,
Obtained as output respectively.

The discrimination output ID from the comparison circuit (21) is the boundary detection circuit (30).
Is supplied to. In this example, the boundary detection circuit (30) detects a horizontal boundary and a vertical boundary. That is, n 1-sample delay circuits (31H) (32
H) (33H) and the table circuit (34H) consisting of ROM etc. constitute a horizontal boundary detection circuit, and the discrimination output
The boundary and its vicinity are detected by pattern matching for n pixels in the horizontal direction of the ID. For example, when a boundary is detected by pattern matching of 3 pixels, 3 pixels are "1".
"1""0","1""0""0","0""0"
When a pattern of "1", "0", "1", "1", is detected in the table (34H), it is regarded as the boundary and its vicinity. Other patterns, such as "1""1""1","0"
"0""0","0""1""0","1""0"
It is determined that "1" is not a boundary. That is, the pattern that changes only once from “0” to “1” or from “1” to “0” is set as the boundary. In addition, "1" next to the boundary "1"
"1" and "0""0""0" may be near the boundary.

From the table (34H), a signal KH that is in a specific state at this horizontal boundary point and its vicinity is obtained.

Similarly, n delay circuits of one horizontal period (31V) (32V) ...
(33V) and the table circuit (34V) constitute a vertical boundary detection circuit, and the vertical boundary and its vicinity are detected by the pattern matching of n pixels in the vertical direction of the discrimination output ID, and the detection thereof. The output KV is obtained from the table (34V).

The filter (50) is a horizontal filter part in this example,
It is composed of a vertical filter unit, and in this example in the horizontal direction and the vertical direction, the sum of products of three pixels is taken for filtering.

That is, two 1-sample delay circuits (51H) (52
H) Three ROMs (53H) (54H) (55H) and two adder circuits (56H) (57H) constitute a horizontal filter section, and the composite image data DV from the multiplexer (41)
Sample data D _i at that time and delay circuit (51H)
And the sample data D _i-1 of the previous sample more, the delay circuit and the two samples preceding the sample data D _i-2 of from (52H), ie each data of three pixels in the horizontal direction ROM
Supplied as a part of (53H) (54H) (55H) address data. Further, horizontal boundary information KH from the table (34H) is supplied as the rest of the address data of these ROMs (53H) (54H) (55H).

And from these ROM (53H) (54H) and (55H),
The sample data from the multiplexer (41) and the delay circuits (51H) and (52H) multiplied by a predetermined coefficient is read out, and the read out data is added to the addition circuits (56H) and (57H). Is added in.

In this case, when the boundary information KH indicates a state other than the boundary and the vicinity thereof, the ROM (5
The coefficients multiplied by (3H) to (55H) are added by the addition circuit (57
It is assumed that the data obtained in H) can be obtained without changing the original sample image data.

On the other hand, when the boundary information KH indicates the boundary and its vicinity, the coefficients multiplied by the ROMs (53H) to (55H) are such that the coefficients are filtered. For example, in the case where the image changes stepwise as shown in FIG. 4, three sample data D _i in the horizontal direction,
ROM (53H) (54H) for D _i-1 , D _i-2 (Fig. 4, A, B, C)
Data obtained by multiplying the coefficient by 1/3 is obtained from (55H), and as a result, the image data of step change is passed through the low-pass filter from the addition circuit (57H) as shown in FIG. 4D. It is possible to obtain the data DM that is made to change smoothly.

Image data that has passed through the horizontal filter section in this way is
Further, it is supplied to the vertical filter unit. This vertical filter section includes a delay circuit (51V) for one horizontal period (52V).
V), ROM (53V) (54V) (55V) and adder circuit (56V) (5
7V), and ROM (53V) to (55V) for the vertical 3 pixel data obtained by the delay circuit (51V) (52V).
V) and adder circuits (56V) (57V) take the product sum in the same manner as in the horizontal direction, and the filtering is performed at the vertical boundary and its vicinity. Therefore, the table (34V)
The vertical boundary information KV from is supplied to the ROMs (53V) to (55V).

In this way, the addition circuit (57V) obtains the image data DO which is filtered only in the horizontal and vertical boundaries and in the vicinity thereof, and is output to the output terminal (64).

In the above example, the case where the filtering is performed on three pixels has been described, but the filtering may be performed on three or more consecutive pixels in the horizontal and vertical directions. Also, RO
The coefficient to be multiplied by M (53H) ~ (55H) and ROM (53V) ~ (55V) is changed at the boundary and its vicinity.
You can also make it less noticeable.

As described above, according to the present invention, the sampling data of pixels only at the boundary between the input image and the background and in the vicinity thereof is filtered once in the horizontal direction and once in the vertical direction, for a total of two times of filtering. I am trying to do it. For this reason, when a figure created by computer calculation is displayed on a raster scan type display, the creases that occur at the boundary between the figure and the background may deteriorate the image quality of the part other than the boundary and its vicinity. Can be reduced without. Therefore, the image quality can be significantly improved as compared with the conventional case where the entire image is filtered.

Further, according to the present invention, since the processing can be performed by hardware, it can be easily realized without imposing any burden on the software of the computer.

Further, in the present invention, since the processing is not related to the property of the created figure or the algorithm for creating the figure, there is an advantage that it is versatile.

[Brief description of drawings]

FIG. 1 is a block diagram of an outline of an example of the device of the present invention, and FIG.
FIG. 4 is a diagram for explaining a crease appearing in a display image, FIG. 3 is a block diagram of an embodiment of a concrete configuration of the device of the present invention, and FIG. 4 is a waveform diagram for the explanation. (10) is an image memory as an input image generating means, (20)
Is a decision circuit, (30) is a boundary detection circuit, (40) is a background image composition circuit, and (50) is a filter.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location 9192-5L G06F 15/72 Z (56) Reference JP-A-59-90161 (JP, A) JP-A-52 -22937 (JP, A) JP 59-103483 (JP, A) JP 58-219683 (JP, A) JP 57-204966 (JP, A) JP 59-43672 (JP, A) )

Claims (1)

[Claims] 1. An image memory in which (a) input image data created by calculation is written and data of a specific color not shown in the input image is written in a background portion of the input image, and (b) this image. The data read from the memory is supplied, and the data part of the specific color is identified as the background and the other data part is identified as the created figure, and a determination means for outputting a determination output, and (c) the determination means described above. A detection means for detecting the boundary between the input image and the background and the vicinity thereof from the discrimination output in the horizontal direction and the vertical direction in parallel by pattern matching and outputting the detection output, and (d) the detection by the detection means. By the output, with respect to the image signal from the image memory, only the boundary between the input image and the background and the vicinity thereof are horizontally connected only at the boundary and the vicinity thereof. The boundary between the input image and the background and the sampling data of the pixels in the vicinity thereof are multiplied by a predetermined coefficient to perform filtering, and only the boundary between the input image and the background and the vicinity thereof are vertical. Regarding the direction, the sampling data of the pixels of the boundary and the vicinity of the input image and the background, and the sampling data of the pixels in the vicinity of the boundary are added to perform filtering. And a filter means for obtaining an output image signal by performing a total of two filtering operations, one each in the horizontal direction and once in the vertical direction.