JPH01251092A - Image output circuit for video system - Google Patents

Abstract

PURPOSE:To more naturally display an image of a real time by giving a coefficient code for narrowing a passing band in case of reducing a image, and widening the passing band in case of enlarging the image, to a digital filter. CONSTITUTION:A signal into which character data and a back code have been mixed by a mixing part 5 is inputted to a D/A converting part 6 through a digital filter 7. The digital filter 7 is constituted so that a passing band of an input signal is changed in accordance with a prescribed coefficient code, and the coefficient code is stored at every picture element unit in an image memory 1. In this state, the coefficient of the digital filter 7 is stored as a value for widening the passing band when an image displayed on a display device 3 is enlarged, and narrowing the passing band when its image is reduced, at every one picture element of the image memory. In such a way, an image displayed on a screen becomes a natural one such as it is looked at actually.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image output circuit that outputs real-time image signals to a display device of a video system configured with a personal computer or the like.

[Conventional Example] Conventionally, this type of image output circuit has a configuration as shown in FIG. 5, for example.

In the figure, a one-image memory 1 stores code data that has been subjected to graphical processing, for example, by a CPU 2 of a personal computer or the like. The code data is obtained based on a sorted list of the coordinate values of the figure to be displayed, and data on nine figures, colors, etc. are stored in the one-image memory 1 for each pixel of the screen coordinates of the display device 3. Furthermore, in the case of a moving image, the CPU 2 compares the newly created sort list with the old sort list, and the data in the image memory 1 is rewritten according to the comparison.

In this way, the data stored in the image memory 1 is read out (refreshed) at regular cycles, and character data corresponding to the data is read out from the character memory 4. At this time, the backcoat (corresponding to the palette) stored in the 1-image memory l is read out together with the above data, the backcoat and character data are mixed in the mixing section 5, and the D/A conversion section 6 The mixed signal is output in analog form from the image output circuit composed of the mixing section 5 and the D/A converting section 6, which is an analog signal (image output signal). 3 displays real-time images. Note that in the case of an actual image processing circuit, the above-mentioned circuit is composed of a plurality of circuits.

[Problems to be Solved by the Invention] By the way, in the video system such as the above-mentioned personal computer, a display device! The real-time screen displayed in 3 is scaled up or down by, for example, displaying the image far away or nearby (perspective display of the image).

However, if you reduce the currently displayed screen,
In other words, when an image is displayed so that it recedes, it is based on the character data read directly from the character memory 4, so the displayed image is too sharp and does not look as natural as the actual image (words). When I changed the image, the image became blurry).

In order to solve this problem, a character memory having character data corresponding to such distances is required, which poses the problem that the character memory becomes enormous.

This invention was made in view of the above problems, and its purpose is to provide an image output circuit for a video system that can display real-time images more naturally without having to have a huge character memory. .

[Means for Solving the Problems] In order to achieve the above object, the present invention converts the character data into analog when the character data is read out corresponding to the code data stored in the image memory. In an image output circuit of a video system that outputs images to a display device.

A digital filter is provided that changes the passband of a signal depending on the image displayed on the screen of the display device.

[Function] In the above configuration, the coefficients of this digital filter are:
For example, each pixel in the image memory is stored with a value that widens the passband when the image displayed on the display device is enlarged, and narrows the passband when the image is reduced.

In other words, when displaying an image that appears far away on the screen (when reducing the image), the passband of the above signal becomes narrower, so the image displayed on the screen does not look as natural as what you actually see. can do.

[Example] Hereinafter, an example of the present invention will be described based on the drawings. In FIG. 1, parts that are the same as those in FIG. 5 are designated by the same reference numerals, and redundant explanation will be omitted.

In FIG. 1, a signal in which character data and backcoat are mixed in a mixing section 5 is input to a D/A converting section 6 via a digital filter 7. The digital filter 7 has a pass band of an input signal changed according to a predetermined coefficient code. The coefficient code is stored, for example, in the image memory 1 for each pixel. Note that 5 image memories 1. Character memory 4, mixing section 5, and digital filter 7 constitute a graphic memory (RAM).

Further, the digital filter 7 has a configuration shown in FIG. 2, for example, and includes a plurality of 1-line memories 7a that store signals mixed by the mixing section 5 for one line of the display device 3. (F I R
inite Io+pulse Re5ponse) filter (for example, 3 lines x 5 taps configuration) 7b. The FIR filter 7b is one of the display devices.
A plurality of one-pixel delay circuits 7b for delaying a pixel, a plurality of adders 7b2, and respective coefficients all all
It consists of a multiplier 7b of a2t aIt as, and so on. In addition, these coefficients ai+ azf a3* a
4p a', the passband of the signal by the digital filter is fβ when the image is close to the distance of the screen, and fα( when the image is far away (image reduction) <fβ).

Next, the operation of the image output circuit having the above configuration will be explained based on the display screens shown in FIGS. 3 and 4.

First, the image memory 1 stores an image to be displayed on the display device W13, for example code data subjected to perspective processing as shown in FIGS. 3 and 4, and other back coat and coefficient codes (transmittance codes; information) is stored.

Here, when displaying an image as shown in FIG. 3 on the screen 3a of the display device 3, under the control of the CPU 2, code data for enlarged display is read out from the image memory 1. The character data of the image is read out from the character memory 4 in accordance with the code data.

At this time, the back coat and coefficient code are also read out for each pixel of the image memory 1. Then, the character data forming the image, the back coat, etc. are mixed in the mixing section 5, passed through the digital filter 7, and converted into analog data in the D/A conversion section 6 to be output as an image. Also, an image like the one shown in Figure 4 (3rd
When displaying a reduced image of the screen in the figure on screen 3a, CP
Under the control of U2, when code data for double-sided reduction is read out from the image memory 1, character data of the image is read out from the character memory 4 in correspondence with the code data. At this time.

Corresponding to these code data, back coat and coefficient codes are also read out for each pixel of the image memory 1. Then, the character data forming the image, the back coat, etc. are mixed in the mixing section 5, passed through the digital filter 7, and converted into analog data in the D/A conversion section 6 to be output as an image.

At this time, when displaying an image as shown in FIG. 3, the passband of the signal in the digital filter is determined by f
β(>fα), and when displaying an image as shown in FIG.
In other words, when the image on the screen of the display device 3 is reduced, the frequency band through which signals forming the image are passed becomes narrower, and distant parts are displayed as a natural image that appears to be actually far away. It becomes like this. In addition, when displaying the image shown in Figure 3, the frequency band through which the signals forming the image are passed is wider than in the case of the image shown in Figure 4 above, so that the closer part can actually be seen closer. The image will now be displayed with sharp edges.

In this way, the coefficient code read out from the one-image memory 1 differs depending on the image displayed on the screen of the display device 3, and the pass band of the signal in the digital filter 7 can be changed. When displaying perspective, you can display a natural image that looks as if you are actually looking at a distance, or a sharp image that looks like you are actually looking at something up close. Moreover, in that case, the character can be converted without changing the code of the character itself.
A significant reduction in memory can be achieved. Furthermore, in addition to displaying the above-mentioned near and far images, it can also be used, for example, to express images through frosted glass. That is, when expressing an image in which an object passes behind frosted glass, the coefficient code of the digital filter may be set to be approximately the same as the above-mentioned reduced display.

In the above embodiment, the coefficient codes of the digital filter 7 are stored in the image memory 1, but they may also be read out from a look-up table in a ROM in which the coefficient codes are stored in advance. Well, you can also set it directly on CPU2, and furthermore,
These coefficient codes may be set not for each pixel in the image memory 1, but for each character data in the character memory 4, or for each moving object on the screen.

[Effects of the Invention] As explained above, according to the present invention, a digital filter is provided that changes the pass band of a signal based on character data and a backcoat (data corresponding to a palette),
If the image to be displayed on the display device is far away (image reduction), the passband will be narrowed, and if the image is close (image enlargement), the passband will be widened. Since the input is applied to the filter, it is possible to display near and far images as if actually seen, without changing the code in the character memory, that is, without having to provide many character ROMs and switching between them. ROM can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of an image output circuit showing an embodiment of the present invention, FIG. 2 is a circuit block diagram showing an embodiment of a digital filter used in the image output circuit,
3 and 4 are diagrams of display screens based on signals obtained by the image output circuit, and FIG. 5 is a schematic block diagram of a conventional image output circuit. In the figure, 1 is an image memory, 2 is a CPU, 3 is a display device, 3a is a display screen, 4 is a character memory, 5 is a mixing section, 6 is a D/A conversion section, 7 is a digital filter, 7a is a line memory, 7a1 is 1 line memory, 7
b is an FIR filter, 7b is a one-pixel delay circuit, 7b
, is an adder, and 7b is a multiplier. Patent applicant: Fujitsu General Co., Ltd. Patent attorney: Takuya Ohara

Claims (2)

[Claims] (1) In an image output circuit of a video system that converts the character data into analog and outputs it to a display device when character data is read out corresponding to code data stored in an image memory, the display device comprises: It has a digital filter that changes the pass band of a signal according to the image displayed on the screen, and the coefficients of the digital filter widen the pass band when the image displayed on the display device is enlarged, and when the image is reduced. An image output circuit for a video system, characterized in that the passband is narrowed when the image is displayed. (2) The digital filter is comprised of a plurality of one-line memories that store the signals corresponding to one line of the screen of the display device, and an FIR filter that receives these stored signals as input. Section (1)
Image output circuit described.