JPS6153692A - Image display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image display device for displaying a plurality of images in a superimposed manner.

[Prior art]

In a device that displays an image by repeatedly reading out an image signal stored in an image memory (also called refresh memory) and outputting it to a display device such as a CRT,
Displaying a plurality of images in a superimposed manner instead of a single image has been conventionally performed, but for this purpose it was necessary to provide a plurality of image memories corresponding to the plurality of images.

FIG. 1 is a block diagram showing an example of the configuration of a conventional image display device. In the figure, 1) to 13 are image memories;
4 is a switch, 15 is a color look amplifier table (hereinafter abbreviated as CLUT), and 16 is a CRT.

In this example, the three image memories 1) to 13 each contain images with different contents (for example, an image of only characters, an image drawn by geometric figures, an image containing general figures, etc.)
These are controlled by a common memory control unit (not shown), and image signals are read out at the same timing. The switch 14 monitors the values of the three types of image signals in real time, and selects and outputs one of the image signals using a predetermined logic circuit. For example, select Sl unless the output Sl of the image memory 1) takes a specific value (a value corresponding to a transparent color), and the output Sl takes the above specific value and the output S2 of the image memory 12 does not take a specific value. In case S2
is selected, and when both Sl and S2 take specific values, the output value S3 of the image memory 13 is selected and output. This selection means St, S2. This is nothing but prioritizing the display in the order of S3. The CLUT 15 is a conversion circuit that converts the signal input from the switch 14 into an actual display color. For example, as shown in FIG. 2, a 4-bit input signal is converted into R, G,
16 types (GO or C) expressed by 4 bits each
Convert to color F). The contents of the CLUT 15 are normally rewritable, and an output value for an input value can be arbitrarily set and written by a CPU (not shown).

In the image display device configured as shown in FIG. 1, images stored in each image memory can be prioritized and displayed in a superimposed manner, but since a single CLU 'l' is shared,
The types of display colors that can be used for each image are common, and as a result, the same image as the one read out through the CLUT is obtained by writing the images one on top of the other in order of priority in one image memory. .

FIG. 3 is a block diagram showing another example of the configuration of a conventional image display device, in which 21 to 23 are CLUTs dedicated to each image memory.
, 24 is a switch that switches the output signals of the plurality of CLUT#s according to the outputs S1 to S3 from each image memory. In an image display device having such a configuration, images stored in each image memory can use CLUTs set to different contents, so images drawn completely independently can be displayed in a superimposed manner.

By the way, in the conventional image display device like the above example,
Since the plurality of image memories have a separate structure, there is a drawback 1 in that the usage of the image memory as a whole is limited by the structure. For example, in the example shown in Figs. 1 and 3, when the outputs S1 to S3 of the three image memories 1) to 13 are each 4 bits, this image display device outputs only one image having data of 5 bits or more for each pixel. It is not possible to display images of

This is simply because, although the three image memories collectively have an MM capacity of 12 bits per pixel, the configuration is such that the capacity cannot be fully utilized. Also, in the above example, an image with 3 bits per pixel @! It is also impossible to display an image by superimposing four images, which also shows that the configuration of the conventional quarter display device lacks flexibility.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and the image memory is capable of storing multiple bits and corresponds to a plurality of all images each having a priority in a storage area of each address. The image signal of one pixel is stored in desired bits, and the CLUT outputs the image signal of the low priority image only when the image signal of the high priority image takes a specific value (value corresponding to transparent color). To provide an image display device which can fully utilize the storage capacity of an image memory and can flexibly change the number of images to be superimposed and the number of bits allocated to one image by setting the contents as follows. It is something.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

Ru. In the figure, reference numeral 41 is an image memory, which stores image signals of one pixel corresponding to all the plurality of images, each having a priority, in desired bits in a storage area at each address that can store a plurality of bits. It is. Also, 4
2 is a CL which inputs all the output signals of the image memory 41;
This is a UT that outputs a signal corresponding to the image signal of a high priority image, and when the image signal takes a specific value, outputs a signal corresponding to the image signal of a low priority image. The contents are set. Note that 16 is CR
It is T.

In this embodiment, the image memory 41 contains 12 bits ii! per pixel. ii image signal can be stored, and its output 12 bits are divided into three groups (G1 to G3) of 4 bits each. By dividing the image memory in this way and setting the CLUT contents by the CPU, which will be described later, the ff
As in the case of FIG. 13, it is possible to display three 4-bit images drawn using independent colors in a superimposed manner.

FIG. 5 is a diagram showing how other display control is performed according to this embodiment. In other display controls, the image (image memory 41
The output of 12 bits is 3 bits, 2 bits, 5 bits, 2 bits.
By dividing the image into four groups of bits, four images are displayed in a superimposed manner.

In the configuration of the image display device according to this embodiment, the image memory 41 is thus arbitrarily divided into a plurality of bits of each storage content, and each of them is assigned to each image for superimposed display of WJijR. Comparing the conventional method shown in FIG. 3 with the one shown in FIG. 4, if the number of bits per pixel in the entire image memory is the same, the capacity of the CLUT 42 shown in FIG. It is larger than the sum of the capacitances of the CLUTs. However, the capacity of the CLUT is small compared to the image memory (for example, the capacity of an image memory with 512 x 512 pixels and 12 bits per pixel is approximately 3 megabits, whereas the capacity of a CLU that outputs 4 bits each for R, B, and G) is small.
The capacity of T42 is 48 bits) and a single CLUT is easier to control when considering the peripheral circuitry for controlling multiple CLUTs as shown in Figure 3.
Increasing the capacity of the CLUT is hardly a problem.

Now, the content setting of the CLUT by the CPU in the image display device according to this embodiment will be described in detail below using a specific example. In the following specific example 1/1), we will discuss the case where the storage of the image in the image memory 41 is 4 bits per pixel for WIR purposes, and therefore the number of input bits to the CLUT 42 is also 4 bits, but other cases will be described. It is easy to understand that it can be similarly applied to
cormorant.

Figure 6 shows the CLtJT42 when the output 4 bits of the image memory 41 are divided into two groups G1 and G2 of 2 bits each, and the image on the Gl side is displayed in a superimposed manner with priority over the image on the G2 side.
This shows an example of content settings. Actual color output from CLUT42 (R.

G, B each consisting of 4 bits) is associated with the input and represented by the symbol CO or CF. In this example, G1 is given priority
CLUT except when the value of 1 is “OO” (i.e. transparent)
The following is set so that the output of 42 is determined only by the value of 01 and the value of G2 is irrelevant. When the value of G1 is 00゛, the output value of CLUT is determined by the value of G2.
Set.

In FIG. 7, the 4-bit output from the image memory 41 is divided into two groups, 1-bit G1 and 3-bit G2.
CLUT when superimposing G2 with priority over 01
42 shows an example of content settings. In this example, G
When the value of G2 is other than °1)1' (in this case, this corresponds to the transparent color of 02), GO=C8, C1 so that the output of CLUT42 is determined only by 02. -C9°C2=C8, C3-CB.

C4-CC, C3-CD, and C6=CE are set. Further, when the value of G2 is "1) 1°, the values of 07 and CF are set so that the output of the CLUT 42 is determined by the value of Gl.

FIG. 8 shows the output bits of the image memory 41, 1 bit each,
This figure shows an example of the content settings of the CLUT 42 in the case where three images are divided into three groups G1 to G3 of 2 bits and 1 bit, and three images are displayed in a superimposed manner, giving top priority to G2 and giving priority to G1 next. In this example, it is assumed that G2 is transparent when it takes the value "00°," and G1 is transparent when it takes the value "0°." Since G2 has the highest priority, the value of G2 is ゛OO
”, the output of CLUT42 is determined only by the value of G2, and since G1 has priority on people, the value of G2 is “0”.
0' and the value of G1 is 1°, the output value of CLUT42 is determined regardless of the value of G3. Set C3=C9 and the contents of CLUT42.

The principle of the method for setting the contents of CL and UT 42 by the CPU is as follows. In other words, among the values taken by the higher priority group, the CLUT output values are determined for all values except the specific value corresponding to the transparent color, and the values taken by other groups are treated as don't care. In other words, the setting value is written to the CLUT, allowing duplication regardless of the values of lower priority groups. At this time, a write prohibition flag is attached to the part where the setting value is written to prevent it from being written to again. Then, when only the specific value corresponding to the transparent color remains, the same process is executed for the next highest priority group, but the part with the write-protect flag is not rewritten. If ^1ri with high priority is executed for all groups, a CLUT with the desired contents will be completed.

In addition to the above methods, rewriting can be prevented by distinguishing parts of the CLUT written to high priority groups by input values (rather than write-protection flags),
Alternatively, the same GLUT result can be obtained by allowing M multiples to be written in the group with the lowest priority and rewriting with the group with the highest priority.
Contents can be set.

As described above, in this embodiment, the multiple bits of the image signal input to the CLUT 42 are divided into arbitrary groups, and the priority is set only when the higher priority group takes a specific value corresponding to the transparent color. Since the contents of the CLUT are set so that the value taken by the lower group is effectively reflected in the CLUT output, it is possible to display the number of images equivalent to the number of divided groups in a superimposed manner, and each group can be independently displayed. We can actually define one color. Incidentally, if we set one specific value corresponding to the transparent color in each group, the input signal of the N-bit CLUT42 can be
l, n2. . . , ni, . . . When grouped into bits (N-Σni), it is possible to define M=Σ(2-1)+1 different actual colors at maximum.

〔Effect of the invention〕

As described above, according to the image display device according to the present invention,
The multi-bit image signal output from the image memory is sent to the CLU.
When displaying an image on a display device via T, the image memory stores the image signal of one pixel corresponding to all the plurality of images with priority in the storage area of each address that can store the plurality of bits, one by one, by desired bits. The contents of the CLUTO are set so that the image signal of the image with lower priority is output only when the image signal of the image with higher priority among the multiple bits input to the CLUT takes a specific value. By doing this, it is possible to display a number of images in a superimposed manner corresponding to the number of divided groups, so the number of images to be superimposed and the W
The number of bits per fJ image can be flexibly set, and the storage capacity of the image memory can be utilized without waste.

[Brief explanation of the drawing]

1 and 3 are block diagrams showing an example of the configuration of a conventional image display device, FIG. 2 is a diagram showing an example of the contents of the color look amplifier table shown in FIGS. 1 and 3, and FIGS. FIG. 5 is a diagram showing an example of the block configuration of an image display device according to an embodiment of the present invention and an example of its display control, and FIGS. 6 to 8 are color look amplifiers in the devices shown in FIGS. 4 and 5. FIG. 3 is a diagram illustrating an example of setting the contents of a table. 1). 12. 13.41...Image memory, 14°2
4...Switcher, 15.21.22.23.42...
Color lookup table, 16...CRT (display device). Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) Repeatedly read out multiple bits of image signals stored in the image memory and use a color lookup table (hereinafter referred to as CL).
In an apparatus for displaying an image on a display device via a UT (referred to as UT), the image memory is capable of storing a plurality of bits in a storage area of each address corresponding to one pixel image of all the plurality of images, each having a priority. The CLUT stores a signal in desired bits, and the CLUT outputs a signal corresponding to the image signal of a high-priority image, and when the image signal takes a specific value, outputs a signal corresponding to the image signal of a low-priority image. An image display device configured to output a signal.