JP3377179B2 - Screen synthesis apparatus and method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of synthesizing a plurality of moving image signals based on a predetermined rule, and particularly to
The present invention relates to screen compositing in the case where alpha data is provided in binary, which is composed of color difference signals.

[0002]

2. Description of the Related Art First, the background of the technology relating to image composition will be described. The image is a background image as shown in FIG. 3 and an object (image combining image) as shown in FIG. 4 to be combined with the background image. In FIG. 4, alpha signal data is provided as a set together with actual image signal data. Here, when synthesizing the synthesizing image with the background image, the alpha signal is a value indicating how much the pixels of the synthesizing image are added to the pixels of the corresponding background image. There is a method of stepwise allocating between the maximum value and the minimum value of this Y signal based on the Y signal of 0 by using 8 bits, such as 0 (= 0%) to 255 (= 100%). That is, the alpha signal is
It has the same amount of data as Y signal pixels of the image for composition, generally has a value of 0 to 255 per pixel, 0 when it is completely transparent, and when it is completely opaque. Indicates 255. At this time, opacity means that the composition image to be combined is 100% dominant, and transparent means that the background image is 100% dominant. Also,
An alpha signal may be automatically assigned to each pixel based on the Y signal of the compositing image, or the operator may allocate the alpha signal while looking at the compositing image. In addition,
In the following description, the data amount means the image size (number of pixels).

In addition, the intermediate values are distributed in large amounts especially in the contour portion of the object of the compositing image, the background and the compositing image are blended to create a halftone image, and the jaggedness of the contour portion is visually smoothed. Has the effect of Then, the combined image is combined and displayed as shown in FIG. 5, for example. However, it is often the case that the alpha value is a binary value, since it is important that the image synthesis can be performed at high speed on a PC having a small computing ability. That is, 0 and 2 as the alpha value
It is a binary value of 55. Also, the alpha data information is often provided with only the data of the same size (number) as the Y signal pixel in consideration of the data amount. Here, when the alpha signal is binarized, the threshold level may be appropriately set and binarized according to the composition image situation. Therefore,
The case where the alpha signal is binarized so as to be compatible with a personal computer (PC) will be described below.

Next, an example of a conventional screen compositing method based on such a background will be shown below with FIG. First, the input image (background image) 81 of the Y color difference signal and the input image (composite image) 82 of the Y color difference signal are supplied to the RGB conversion circuits 84 and 85, respectively. Previously, the alpha signal had the same magnitude as the Y signal, and image processing on a PC etc.
Since it was done in B format, input images 81, 82
Is converted to RGB format. Separately from this, the alpha signal 83 corresponding to the input image (composite image) 82 of the Y color difference signal is supplied to the alpha value detection circuit 86.

The alpha value detection circuit 86 is premised on that the alpha value is binary. That is, it is detected whether the pixel of the Y color difference input image 82 is transparent or opaque,
The determination result is supplied to the synthesis control circuit 87. In the synthesizing control circuit 87, if the image is transparent, the input image (synthesis image) 8
The data of 2 is transmitted to the synthesizing circuit 88 as 0, and when it is opaque, the data of the input image 82 itself is synthesized.
Send to 8. The synthesizing circuit 88 synthesizes the data of the input image 82 with the input image (background image) 81 in accordance with the output from the synthesizing control circuit 87. Synthesis circuit 8
In the Y color difference conversion circuit 89, the signals combined by 8 are converted from RGB into Y color difference signals and output.

[0006]

[Problems to be solved] By the way, since the alpha signal has the same data amount as the Y signal pixel in the past, when converting the input image to RGB, all the RGB converted images have the same data amount as the alpha data before processing. I did it, but on PCs and computers with small computing power, Y color difference-RGB conversion, RGB-Y
Color difference conversion is a very heavy processing. Therefore Y
If color difference-RGB conversion and RGB-Y color difference conversion were not performed, the number of pixels of the alpha data and the number of pixels of the color difference signal would be different, so processing could not be performed as it was.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems. According to the invention of claim 1, a background image composed of a Y color difference signal and an image for synthesis are combined with each other. In a screen synthesizing method of synthesizing an alpha signal associated with the Y signal in the same data amount as the Y signal, the alpha signal is band-limited, and then the alpha signal has the same data as the color difference signal of the synthesizing image. Subsample to a quantity to create an alpha signal for the color difference signal,
When the Y signals of both images are combined, the alpha signal is used, and when the color difference signals of both images are combined,
A screen was synthesized using the alpha signal for the color difference signal. According to a second aspect of the present invention, the background image composed of the Y color difference signal and the combining image are combined using the alpha signal associated with the Y signal in the same data amount as the Y signal of the combining image. In a screen synthesizing device, a low-pass filter to which the alpha signal is supplied, a sub-sampling circuit that converts the alpha signal into the same data amount as the color difference signal of the image for synthesis, and a color difference that detects an alpha value for the color difference signal. For detecting a color difference signal, a color difference signal combining control circuit for controlling a color difference signal of a combining image to be combined with the background image from the alpha signal for the color difference signal, and a Y signal for detecting an alpha value of the Y signal An alpha value detection circuit, a Y signal combination control circuit for controlling a Y signal of a combination image to be combined with the background image from the Y signal alpha signal, Image, the color difference signal synthesizing control circuit output, and was composed of a combining circuit for combining the Y signal combining control circuit output. The invention according to claim 3 is Y
In a screen synthesizing method of synthesizing a background image composed of color difference signals and a synthesizing image using an alpha signal associated with the Y signal in the same data amount as the Y signal of the synthesizing image, a pixel position of the color difference signal The alpha signal for the color difference signal is created by the number of pixels indicating the transparency of the alpha signal corresponding to, and when the Y signals of both images are combined, the input alpha signal for the Y signal is used, and the color difference signal of the both images is used. When synthesizing, the screen was synthesized using the alpha signal for the color difference signal. The invention according to claim 4 is Y
In a screen synthesizing device for synthesizing a background image composed of color difference signals and a synthesizing image using an alpha signal associated with the Y signal in the same data amount as the Y signal of the synthesizing image, a pixel for the color difference signal A color difference alpha signal calculation circuit that creates an alpha signal for a color difference signal by the number of pixels indicating transparency of the alpha signal corresponding to a position, a color difference alpha value detection circuit that detects an alpha value of the color difference signal, and a color difference signal for the color difference signal. A color difference signal combination control circuit for controlling a color difference signal of a combination image to be combined with the background image from an alpha signal, a Y signal alpha value detection circuit for detecting an alpha value of the Y signal, and an alpha signal of the Y signal From the Y signal combining control circuit for controlling the Y signal of the combining image to be combined with the background image, the background image, the color difference signal combining control circuit output, and It was composed of a combining circuit for combining the serial Y signal combining control circuit output.

According to a fifth aspect of the present invention, in the screen synthesizing method according to the third aspect, when the Y color difference signal format is 4: 2: 0, the pixel of the alpha signal corresponding to the pixel position of the color difference signal. When any one of the four values of the pixel is opaque, the color difference signal is calculated by making the alpha value for the color difference signal opaque, or when any one of the four values of the pixel is transparent, the color difference signal is calculated. The color difference alpha signal is calculated by making the alpha value for use transparent. According to a sixth aspect of the invention, in the screen synthesizing method according to the third aspect, when the Y color difference signal format is 4: 2: 0, four of the pixels of the alpha signal corresponding to the pixel position of the color difference signal are included. When two or more of the values are opaque, a color difference alpha signal calculation is performed to make the alpha value for the color difference signal opaque, or when two or more of the four values of the pixel are transparent, an alpha for the color difference signal is calculated. The color difference alpha signal is calculated so that the value is transparent. The invention according to claim 7 is the screen synthesizing method according to claim 3,
When the Y color difference signal format is 4: 2: 2, if even one of the two values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal is opaque, whether the alpha value for the color difference signal is opaque Alternatively, when even one of the two values of the pixel is transparent, the color difference alpha signal calculation is performed to make the alpha value for the color difference signal transparent.

(Operation) According to the screen synthesizing method and apparatus configured as described above, the screen synthesizing can be performed with the signals as they are without performing Y color difference-RGB conversion and RGB-Y color difference conversion. The processing amount can be greatly reduced. Further, since the alpha signal associated with the Y signal of the image for synthesis is subsampled to create the alpha signal for the color difference signal, it is possible to synthesize the color difference image as it is. Further, according to the data amount of the color difference signal, the alpha signal data for the color difference signal can be calculated by a method with a very small amount of processing instead of sub-sampling the alpha signal, so that the amount of processing can be further reduced.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a screen composing method and apparatus according to the present invention will be described below with reference to FIGS. 1 is a block diagram of an embodiment relating to claims 1 and 2, and FIG. 2 is a block diagram of an embodiment relating to claims 3 to 7. First, a first embodiment of the screen synthesizing method and apparatus of the present invention will be described with reference to FIG. The Y signal and the color difference signal from the input background image (background image) 11 of the Y color difference signal are supplied to the synthesizing circuit 20. The Y signal from the input combined image (composite image) 12 of the Y color difference signal is supplied to the Y signal combination control circuit 19, and the color difference signal is input to the combination control circuit 17. Separately from this, the alpha signal 13 corresponding to the input composite image 12 of the Y color difference signal is input to the Y alpha value detection circuit 18. The alpha signal 13 is set in advance in association with the Y signal of the input compositing image 12, and here, the Y signal value is binarized by setting an appropriate threshold level.

The Y-alpha value detecting circuit 18 detects whether the pixels of the image 12 for compositing are transparent or opaque, and supplies the determination result to the Y-signal compositing control circuit 19. In addition,
Since the alpha signal 13 has been binarized, the Y alpha value detection circuit 18 may simply determine the binary value. In the Y signal composition control circuit 19, if it is transparent, the composition image 1
The Y signal data of 2 is set to 0 and transmitted to the synthesizing circuit 20,
On the other hand, when it is opaque, the Y signal data itself of the image 12 for composition is transmitted to the composition circuit 20. The synthesizing circuit 20 synthesizes the data of the synthesizing image 12 with the background image 11 in accordance with the output from the Y signal synthesizing control circuit 19.

On the other hand, the alpha signal 13 associated with the Y signal of the Y color difference signal synthesizing image 12 is a low-pass filter 14.
To the sub-sampling circuit 15 after being band-limited. The alpha signal 13 is subsampled by the subsampling circuit 15, the number of pixels is thinned out to the same image size as the color difference signal, and the alpha signal for the color difference signal is obtained with the same data amount as the color difference signal. For example
In the case of Y: Cr: Cb = 4: 2: 2 signal, as shown in FIG. 7, the color difference signal is horizontally half the size of the Y signal. Is horizontally halved and subsampling is horizontally halved by the sampling circuit 15. Also, Y: Cr: C
In the case of b = 4: 2: 0 signal, as shown in FIG. 6, the color difference signal is 1/2 the size of the Y signal in both horizontal and vertical directions. In this case, therefore, the band limitation is 1 in both horizontal and vertical directions. The sampling circuit 15 also samples / 2 and sub-sampling so that it becomes 1/2 in both horizontal and vertical directions.

Thereafter, the sampled alpha signal for the color difference signal is supplied to the color difference alpha value detection circuit 16. The alpha signal for the color difference signal detects whether the pixel of the Y color difference input image 12 is transparent or opaque in the color difference alpha value detection circuit 16 as well as the Y signal, and determines the determination result as the color difference signal synthesis control circuit. Supply to 17. Again Y
Similar to the signal, since the alpha signal for the color difference signal is binarized in advance, the color difference alpha value detection circuit 16 may only determine the binary value. In the synthesizing control circuit 17, when it is transparent, the data of the color difference signal of the Y color difference input image 12 is set to 0.
Is transmitted to the synthesizing circuit 20, and when it is opaque, the data of the color difference signal of the Y color difference input image 12 itself is synthesized.
Send to 0. The synthesizing circuit 20 compares the Y color difference input image (background image) 11 with the Y color difference input image (synthesis image).
The 12 pieces of data are combined according to the outputs from the combination control circuits 17 and 19. In this way, the Y signal is combined using the input alpha signal for the Y signal, and the color difference signal is combined using the input alpha signal for the color difference signal.

Next, a second embodiment of the screen synthesizing method and apparatus of the present invention will be described below with reference to FIG. The input image (background image) 21 of the Y color difference signal and the input image (composition image) 22 of the Y color difference signal are input to the synthesis circuit 30, the Y signal synthesis control circuit 29, and the color difference signal synthesis control circuit 27, respectively. Separately from this, the alpha signal 23 corresponding to the input composite image (composite image) 22 of the Y color difference signal is input to the Y alpha value detection circuit 28. The Y alpha value detection circuit 28 detects whether the Y signal pixel of the Y color difference input image 22 is transparent or opaque, and inputs the determination result to the Y signal synthesis control circuit 29. In the synthesizing control circuit 29, in the case of being transparent, the data of the synthesizing signal 22 is set to 0 and the synthesizing circuit 30 is set.
To the input and, conversely, if it is opaque, the input synthesis signal 2
The second data itself is transmitted to the synthesis circuit 30. The synthesizing circuit 30 synthesizes the data of the synthesizing image 22 with the background image 21 in accordance with the output from the synthesizing control circuit 29. The contents up to this point are the same as those in the first embodiment.

On the other hand, the alpha signal 23 associated with the Y signal of the input composite image (composite image) 22 of the Y color difference signal is converted by the color difference alpha signal calculation circuit 25 into a color difference alpha value by a predetermined method described later. It After that, the calculated alpha signal for the color difference signal is input to the color difference alpha value detection circuit 26. This color difference alpha value detection circuit 2
Similarly to the Y signal, 6 also detects whether the pixel is transparent or opaque and inputs the determination result to the color difference signal synthesis control circuit 27.

In the synthesizing control circuit 27, the data of the input signal 22 is transmitted to the synthesizing circuit 30 when it is transparent, and when it is opaque, the data of the input signal 22 itself is transmitted to the synthesizing circuit 30. The synthesizing circuit 30 synthesizes the data of the synthesizing image 22 with the background image 21 in accordance with the outputs from the synthesizing control circuits 27 and 29. In this way, the Y signal is combined using the input alpha signal 23 for the Y signal, and the color difference signal is combined using the input alpha signal for the color difference signal.

Next, the operation of the color difference alpha signal calculation circuit 25, which is the main part of the second embodiment, will be described. First, FIG.
As shown in, in the case of a 4: 2: 2 signal, the size of the color difference signal is 1/2 that of the Y signal, so that for one pixel of the color difference signal, the Y signal has two horizontal pixels. Corresponds. Further, as shown in FIG. 6, in the case of the 4: 2: 0 signal, the color difference signal is 1/2 in both the horizontal and vertical directions with respect to the Y signal.
Therefore, in this case, one pixel of the color difference signal corresponds to two pixels of the Y signal in the horizontal direction and two pixels in the vertical direction, that is, a total of four pixels.

Paying attention to this, when the Y color difference signal format is 4: 2: 0, (1) when all four values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal are opaque, the color difference Determine to make the alpha value of the signal opaque. (2) When even one of the four values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal is transparent, it is determined that the alpha value of the color difference signal is transparent. These two methods are effective in accurately displaying the outline of an object by catching the object a little smaller.

(3) When all four values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal are transparent, it is determined that the alpha value of the color difference signal is transparent. (4) When even one of the four values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal is opaque, the alpha value of the color difference signal is determined to be opaque. These two methods are effective in accurately displaying the outline of the object by catching the object a little larger.

(5) When two or more of the four values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal are opaque, the alpha value of the color difference signal is determined to be opaque. (6) When two or more of the four values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal are transparent, it is determined that the alpha value of the color difference signal is transparent. These two methods are effective in properly placing the color difference signal on the contour of the object.

The Y color difference signal format is 4: 2:
In the case of 2, (1) when the two values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal are all transparent, the alpha value of the color difference signal is determined to be transparent. (2) When even one of the two values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal is opaque, the alpha value of the color difference signal is determined to be opaque. These two methods are effective in accurately displaying the entire object by catching the object in a slightly larger size in the horizontal direction.

(3) When the two values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal are all opaque, the alpha value of the color difference signal is determined to be opaque. (4) When even one of the two values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal is transparent, it is determined that the alpha value of the color difference signal is transparent. These two methods are effective in accurately displaying the contour by catching the object in the horizontal direction a little smaller.

[0023]

According to the present invention, Y color difference-RGB conversion, RGB-Y
Since screen composition can be performed without performing color difference conversion, the amount of calculation processing can be greatly reduced. Further, since the alpha signal can be subsampled according to the size of the color difference signal, the color difference image can be combined as it is. Also, instead of sub-sampling the alpha signal according to the size of the color difference signal, the alpha signal data for the color difference signal can be calculated by a method with a very small amount of processing, so the amount of processing can be further reduced, and the computing power can be improved. Even a small PC or computer can combine images.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of a screen compositing device of the present invention.

FIG. 2 is a block diagram of a second embodiment of the screen compositing device of the present invention.

FIG. 3 is an explanatory diagram of a background in the case of image combination.

FIG. 4 is an explanatory diagram of object data and alpha signals in the case of image synthesis.

FIG. 5 is an explanatory diagram of a combined image in the case of image combination.

FIG. 6 is an explanatory diagram of a 4: 2: 0 image format.

FIG. 7 is an explanatory diagram of a 4: 2: 2 image format.

FIG. 8 is a block diagram of an example of a conventional screen compositing device.

[Explanation of symbols]

11, 21 ... Y color difference signal input (background image) circuit, 12,
22 ... Y color difference signal input (composite image) circuit, 13, 23
... alpha signal circuit, 14 ... low-pass filter, 15 ...
Sub-sampling circuit, 16, 26 ... Y alpha value detection circuit, 17, 27 ... Color difference signal synthesis control circuit, 18, 2
8 ... Color difference alpha value detection circuit, 19, 29 ... Y signal synthesis control circuit, 20, 30 ... Synthesis circuit, 25 ... Color difference alpha signal calculation circuit

Claims (7)

(57) [Claims] 1. A screen synthesizing method for synthesizing a background image composed of Y color difference signals and a synthesizing image by using an alpha signal associated with the Y signal in the same data amount as the Y signal of the synthesizing image. , Band limiting the alpha signal,
After that, the alpha signal is subsampled to the same data amount as the color difference signal of the image for synthesis to create an alpha signal for the color difference signal, and when the Y signals of both images are synthesized, the alpha signal is used, A screen synthesizing method, characterized in that, when synthesizing the color difference signals of the both images, the screen is synthesized using an alpha signal for the color difference signal. 2. A screen synthesizing apparatus for synthesizing a background image composed of Y color difference signals and a synthesizing image by using an alpha signal associated with the Y signal in the same data amount as the Y signal of the synthesizing image. , A low-pass filter to which the alpha signal is supplied, a sub-sampling circuit that converts the alpha signal into the same data amount as the color difference signal of the image for combining, and a color difference alpha value detection that detects an alpha value for the color difference signal A circuit, a color difference signal combination control circuit for controlling a color difference signal of a combination image to be combined with the background image from the color difference signal alpha signal, and a Y signal alpha value detection circuit for detecting an alpha value of the Y signal And the above Y
A Y signal synthesis control circuit for controlling a Y signal of a synthesis image to be synthesized with the background image from an alpha signal for a signal, the background image, the color difference signal synthesis control circuit output, and the Y signal synthesis control circuit output. A screen synthesizing device comprising a synthesizing circuit for synthesizing. 3. A screen synthesizing method for synthesizing a background image composed of Y color difference signals and a synthesizing image by using an alpha signal associated with the Y signal in the same data amount as the Y signal of the synthesizing image. , An alpha signal for the color difference signal is created by the number of pixels indicating transparency of the alpha signal corresponding to the pixel position of the color difference signal, and when the Y signals of both images are combined, the input alpha signal for the Y signal is used, A screen synthesizing method, characterized in that, when synthesizing the color difference signals of the both images, the screen is synthesized using an alpha signal for the color difference signal. 4. A screen synthesizing apparatus for synthesizing a background image composed of Y color difference signals and a synthesizing image using an alpha signal associated with the Y signal in the same data amount as the Y signal of the synthesizing image. A color-difference alpha-signal calculation circuit that creates an alpha signal for the color-difference signal by the number of pixels indicating transparency of the alpha signal corresponding to the pixel position for the color-difference signal,
A color difference alpha value detection circuit for detecting an alpha value of the color difference signal, a color difference signal combination control circuit for controlling a color difference signal of a combination image to be combined with the background image from the color difference signal alpha signal, and the Y signal An alpha value detection circuit for a Y signal for detecting the alpha value of the Y signal, a Y signal synthesis control circuit for controlling a Y signal of a synthesis image to be synthesized with the background image from the alpha signal of the Y signal, the background image, A screen synthesizing device comprising: a color difference signal synthesizing control circuit output and a synthesizing circuit for synthesizing the Y signal synthesizing control circuit output. 5. The screen synthesizing method according to claim 3, wherein when the Y color difference signal format is 4: 2: 0, one of four values of the pixels of the alpha signal corresponding to the pixel position of the color difference signal. However, when it is opaque, the color difference alpha signal is calculated so that the alpha value for the color difference signal is opaque, or when any one of the four values of the pixel is transparent, the alpha value for the color difference signal is made transparent. A screen compositing method characterized in that a color difference alpha signal is calculated. 6. The screen synthesizing method according to claim 3, wherein when the Y color difference signal format is 4: 2: 0, among the four values of the pixel of the alpha signal corresponding to the pixel position of the color difference signal. When two or more are opaque, the color difference alpha signal is calculated so that the alpha value for the color difference signal is opaque, or when two or more of the four values of the pixel are transparent, the alpha value for the color difference signal is transparent. A method of synthesizing a screen, characterized in that a color difference alpha signal is calculated. 7. The screen synthesizing method according to claim 3, wherein when the Y color difference signal format is 4: 2: 2, 2 of the pixels of the alpha signal corresponding to the pixel position of the color difference signal.
If any one of the two values is opaque, the alpha value for the color difference signal is opaque, or if any one of the two values of the pixel is transparent, the alpha value for the color difference signal is transparent. A screen compositing method characterized in that a color difference alpha signal is calculated.