JPS61209485A - 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] [Summary] An image display device in which an image memory that stores image data in an area slightly larger than a display area is divided into a plurality of blocks, and the starting coordinates of the image memory and the current display area are divided into blocks. The value of the difference from the first coordinate of It is configured to load data.

This makes it possible to perform seamless, continuous scrolling (continuously moving the image horizontally or vertically on the display screen) using a relatively small-capacity image memory.

[Industrial Application Field] The present invention relates to an image display device, and more specifically,
The present invention relates to an image display device that can select an arbitrary position from a virtual image space and display the image by freely scrolling it vertically and horizontally.

[Prior Art] In an image display device, if all image data is stored in its memory, the display area can be freely scrolled and displayed. In addition, as the amount of data increases, the amount of memory must become extremely large.

On the other hand, although it is possible to reload all image data from the upper memory where it is stored, continuous scrolling without breaks is impossible.

[Problems to be Solved by the Invention] The present invention provides a novel image display device that allows virtually existing image data to be displayed seamlessly by scrolling using a relatively small memory capacity. This is what we are trying to provide.

[Means for Solving the Problems] FIG. 1 shows a block diagram of the principle of an image display device of the present invention.

In Figure 1, ■ is a display, and 2 is a DMA that directly controls transfer between memories without the control of the central processing unit.
The control circuit 3 is an image memory.

4 and 5 are X for storing the start coordinate values (XI, Yl) of the image data stored in the image memory 3, respectively.
The I register and the Yl register. 6 and 7
are an X2 register and a Y2 register that respectively store the leading coordinate values (X2.Y2) of the display area currently displayed on the display 1.

8 is an X@ calculator that calculates (X2-XI), 9 is (Y
This is a YM calculator that calculates 2 Yl). 10 is X
An X comparator that compares the output (X2
or when (X2 XI) > α2, the output is sent to the DMA control circuit 2.

Reference numeral 12 denotes a large-capacity upper memory that stores all image data, such as a main memory of a processing device or a large-capacity memory dedicated to image processing.

The image memory 3 is divided into a plurality of blocks in both the X direction and the Y direction, and when the mouth MAi control circuit 2 receives the output from the X comparator 10, the image memory 3 is
Image data is loaded in units of block columns in the Y direction.

Similarly, 11 is a Y comparator which converts the output of the Y subtracter 9 to a reference value β1. When it is compared with β2 and becomes (Y2-Yl) <βl or (Y2-Yl)>β2, it is sent to the 18 control circuit 2, and the DMA control circuit 2 sends it from the upper memory 12 to the image memory 3. Load image data in units of block columns in the X direction.

[Function] When the image memory 3 is configured so that its left end and right end and its upper end and lower end are linked (usually the display memory is configured like this), the display WJ surface is scrolled to display the image. When the memory boundary is exceeded, the left and right or top and bottom images are combined into a display, so-called wrap.
), and before crossing the boundary, load the image data of the side you are trying to cross into a certain area on the opposite side of the memory, as if all the image data were in the image memory. , which has a seamless scrolling function.

In order to detect when the display screen is scrolled by the operator observing the image and approaches the boundary of the image memory 3, the start coordinate (XI) of the image memory 3 is detected.

Yl) and the top coordinates (X2.Y2) of the display area currently displayed on the display 1, and compares this with a predetermined reference value.

For example, if (X2 XI ) < αl, then
This indicates that the display area has approached the left boundary of the image memory 3, and if (X2-Xl)>α2, it indicates that the display area has approached the right boundary of the image memory 3.

A display 1 displays image data from an image memory 3 through a DMA control circuit 2.

The image memory 3 is divided horizontally and vertically into a plurality of blocks, and when the output from the X comparator and the
Image data adjacent to the boundary to be crossed is transferred from the upper memory 12 to the block column.

[Example] The gist of the present invention will be specifically explained below with reference to the principle block diagram shown in FIG. 1 and the examples shown in FIGS. 2 and 3.

FIG. 2(a) shows the relationship between the image data A stored in the image memory 3 and the display area B currently displayed on the display 1. The starting coordinate value of image data A is (XI
, Yl), the leading coordinate value of display area B is (X2.
Y2).

FIG. 2(b) shows that the image memory 3 is divided into 4 blocks in the horizontal direction and 4 blocks in the vertical direction, that is, 4×4=16 blocks. At the same time, the image is scrolled by the operator's operation using a tablet or the like and moved to the left from the position shown in the figure (al), indicating that the condition (X2 XI) <α1 is satisfied.

FIG. 2(C) shows that the situation as shown in FIG. 2 (bl) occurs, and upon receiving the output from the On the other hand, the image data on the left side of blocks 1 to 4 is stored in the upper memory 1.
This shows the results loaded from 2.

That is, the left ends of blocks 1 to 4 and the right ends of blocks 13 to 16 are linked.

For upward scrolling, (Y2 Yl)
When the condition of βi is satisfied, the upper image data of the block 1.5.9.13 is loaded into the block 4.8.12.16. Scrolling to the right and downward 1ii1 is performed in the same manner in the opposite direction.

By performing the above processing, it is possible to scroll freely as if all the image data were in the image memory 3.

In this embodiment, the image memory 3 is divided into 4 x 4 blocks, but if the number of divisions is changed, the following relationship will be obtained, so the size of the display screen, the transfer speed of the memory, and the speed of scrolling will change. You can select the most suitable one from among them.

(2) The larger the number of divisions, the smaller the ratio of image memory capacity to display area.

(2) As the number of divisions increases, the frequency of image data transfer increases, but the amount of data transferred at one time decreases.

In Figure 3, the number of divisions of the image memory 3 is increased to 16 x 16.
An example is shown below.

[Effects of the Invention] As explained above, according to the present invention, a seamless scrolling function can be provided using a relatively small-capacity image memory, as if all image data were in the image memory, which is practical. The effects are huge.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a configuration diagram of an image memory in an embodiment of the invention, and FIG. 3 is a configuration diagram of an image memory in another embodiment of the invention. In the drawings, 1 is a display, 2 is a DMA control circuit, 3 is an image memory, 4, 5, 6.7 are registers, 8.9 is a subtracter, 10.11 is a comparator, and 12 is an upper memory. . % January 2 This invention's deo self t1

Claims (1)

[Scope of Claims] An image display device that displays a part of image data in an upper memory (12) that stores image data, comprising an image memory (3) that stores image data that completely encompasses a display area; , a subtractor (
8), (9), and comparators (10), (11) that compare the difference value output with first and second reference values, and the difference value output compares with the first and second reference values.
is smaller than the reference value or larger than the second reference value, the image memory (3) is divided into a plurality of blocks, and for each block column unit, the upper memory is (12) An image display device characterized in that it is configured to load image data from.