JP2002290718A - System and method for displaying image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system for displaying such an image as a map or the like via a communications network which can smoothly and sequentially perform the scrolling and scaling up and down of the image. SOLUTION: In displaying a map, for example, a map server 10 is provided with a plurality of entire map data 110, 111, and 112 that are all different in scaling with regard to an identical entire region. Each of the scale-different entire map data is divided into a number of fraction map data dealing with every small region subdivided from the whole map. A map displaying program 32 in a client's computer selectively downloads, via the Internet 20, the regional fraction map data to be displayed in response to the scrolling or scaling up or down operations by the user and displays the regional map image. When the map displaying program 32 downloads a plurality of fraction map data of a different scale regarding an identical region, it assigns priority to smaller- scaled fraction map data in downloading and displaying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a system for a client computer to receive and display image data from an image server through a communication network such as the Internet.

[0002]

2. Description of the Related Art In a conventional system of this type, for example, a map display system, when a user performs an operation on a client computer to change a map display range such as scrolling or enlarging / reducing a map displayed on a screen. The client computer requests a map image of a new map display range from the map server. The map server reads the map data of the new map display range from the database of the server, draws a bitmap map image of the new map display range from the map data, and stores the bitmap map image in the client computer. Send to
The client computer receives and displays the bitmap map image.

[0003]

A problem with the conventional system is that scrolling and enlargement / reduction of a display image such as a map cannot be continuously and smoothly performed. That is,
When the user scrolls or scales the map, the server waits for a while until the server finishes drawing the map image in the new map display area and returns it, and then the map image on the screen is updated The display is switched to the map image in the appropriate map display range. This is a discontinuous switch, just as a web browser jumps from one page to another. Only after the map image on the screen is switched after waiting for a while in this way, the user knows where the scroll destination is, or what the magnification after the enlargement / reduction is. In this case, the user cannot obtain the operational feeling of scrolling or enlarging or reducing the map at all, which is very difficult to use. This problem becomes more prominent as the waiting time becomes longer due to circumstances such as a large number of users accessing the server or a busy communication line.

Accordingly, an object of the present invention is to make it possible to continuously and smoothly scroll and enlarge / reduce an image in an image display system using a communication network.

[0005]

According to the present invention, in a system for transmitting image data from an image server to a client through a communication network and displaying the image on the client, the image server includes a plurality of whole image data having different scales. And the entire image data of each scale is
The whole image is divided into a plurality of pieces of fragment image data each representing an image of a small region obtained by subdividing the whole image into regions. And
In response to a user operation of scrolling or enlarging or reducing the display on the client, fragment image data required for display is selected from a large number of fragment image data in the image server and transmitted from the image server to the client through the communication network. Is done. The client draws and displays an image using the fragment image data received from the image server.

According to this image display system, the client selectively downloads the fragment image data necessary for display from the image server and displays it in response to a user operation of scrolling or enlarging or reducing the display. Since the entire image data is subdivided into a large number of fragment map data, it can be displayed first from the fragment map data that can be downloaded quickly. As a result, scrolling and scaling of the image can be continuously and smoothly performed.

In a preferred embodiment, when a plurality of pieces of fragment image data having different scales are transmitted from the image server to the client, the pieces of fragment image data having the smaller scale are transmitted preferentially. As a result, a progressive display in which the images are sequentially displayed from the small-scale image to the large-scale image is performed, and as a result, when the user performs an operation of scrolling or scaling the image, the image is promptly displayed. Is started, and scrolling and enlargement / reduction of an image can be continuously and smoothly performed.

In a preferred embodiment, a plurality of image servers are provided, and a client can download fragment image data from any of the plurality of image servers. As a result, the load on each image server is reduced, and as a result, image data can be downloaded at high speed, and scrolling and scaling of images can be continuously and smoothly performed.

[0009]

FIG. 1 shows a schematic overall configuration of an embodiment in which an image display system according to the present invention is applied to map display.

A map server 10 for providing a map providing service
And a large number of client computers 30 used by a large number of users, respectively, for example, via a communication network such as the Internet 20. The map server 10 has a map database 11 that stores map data of a wide area. The client computer 30 has a client program 31 for accessing the map server 10. A map display program 32 for sending a specific map data request to the map server 10 and displaying the map data received from the map server 10 is attached to the client program 31 in the form of, for example, a plug-in. . The client computer 30 includes a display device 33 and a mouse 3
4 is also provided.

In this embodiment (although this need not be the case), the map server 10 is a WWW server, the client program 31 in the client computer 30 is a WWW browser, and both are HTTP.
Requests and exchanges map data by protocol.

FIG. 2 explains the types of maps possessed by the map server 10 and the order in which the map display program 32 in the client computer 30 requests map data from the map server 10.

The map database 11 of the map server 10 stores data of a plurality of types of maps 110 to 112 having different scales. In the illustrated example, three types of a large-scale map (a so-called city map) 110 of 1/2500, a medium-scale map 111 of 25,000, and a small-scale map 112 of 200,000 are provided. Stored (of course, more types of maps may be stored).

Maps 110 to 112 of these different scales
Are small rectangular areas (hereafter referred to as the small rectangular areas) that divide the wide area covered by the map into latitude and longitude directions.
It is divided into map data in units of “mesh”. The map data is transmitted from the map server 10 to the map display program 32 in units of one mesh. That is, in one HTTP session between them,
The map data of one mesh is stored in the map display program 32.
, And the map data of one mesh is returned from the map server 10 to the map display program 32. Therefore, as the size (area) of the mesh is smaller, the amount of map data of the mesh is smaller, and the time required for one HTTP session is shorter. Therefore, the time required for displaying one mesh is shorter. However, the smaller the size (area) of the mesh, the larger the number of meshes included in the display range of the map desired by the user, so that the number of HTTP sessions performed between the map display program 32 and the map server 10 is reduced. Increase. From this viewpoint, in order to end the display of the display range of the map desired by the user at a high speed (or to make the user feel like that), the map data amount of one mesh is appropriate and 1 The size of one mesh, that is, the data of one mesh, so that the time required for one HTTP session is not too long and the number of HTTP sessions required for the display range of the map desired by the user is not too large. It is important to set the amount appropriately. For this reason, different scales of the map have different mesh sizes. That is, the smaller the map (ie, the larger the denominator of the scale), the larger the area area that can be covered by the same map data amount, so the mesh size is set to be large (however, the data amount of one mesh is small). Not all maps 110-112 are the same).

The map display program 32 in the client computer 30 grasps the display range of the map desired by the user in accordance with the user's operation of scrolling or enlarging or reducing the map with the mouse 34 or the like, and overlaps with the display range ( In other words, a mesh that is included in the display range or that includes the display range) is determined for each of the maps 110 to 112 of each scale. For example, in the case of the example of the display range of the map shown in the display device 33 in FIG. 2, the meshes overlapping the display range are 16 meshes 110A to 110P of the large-scale map 110 (in FIG. The boundary is shown), and the medium-scale map 111
(The boundaries are indicated by solid lines in the figure) and one mesh 112A of the large-scale map 112. These meshes 110A-11
After determining 0P, 111A to 111D and 112A, the map display program 32 requests the map server 10 for the map data of those meshes. At this time, the map display program 32 gives priority to the small-scale map, that is, first, the mesh 112A of the small-scale map 112,
Next, meshes 111A to 111 of the medium scale map 111
D. Finally, mesh mesh 11 of large scale map 110
A mesh data request is issued to the map server 10 in the order of 0A to 110P. However, the display range determined by the user's enlargement / reduction operation is a wide area, and therefore, a map on a scale larger than a certain scale (for example, a large scale map 110)
Is not required, the mesh of the unnecessary map (for example, the large-scale map 110) is not required.

The map server 10 reads the map data of each mesh from the map database 11 in the requested order, and returns the map data to the map display program 32. as a result,
The map display program 32 can usually receive and display the mesh data of a smaller scale map first (although the order may sometimes be changed depending on the circumstances of the communication network). As described above, the smaller the scale of the map, the larger the size of one mesh, so that the entire area of the display range desired by the user can be covered with a smaller number of meshes. Therefore, a smaller scale map is displayed at high speed over the entire display range desired by the user.
After that, a larger scale map is displayed. Larger scale maps represent more detailed features. Therefore, in the display range desired by the user, a rough feature display of the small-scale map first appears at high speed, and thereafter, a detailed feature display of the larger-scale map appears.

By adopting the progressive map display method using a plurality of types of maps having different scales as described above, when the user scrolls or enlarges or reduces the map, a rough small-scale map is displayed immediately. So users no longer feel like they're switching between maps after a while,
It is possible to obtain an operational feeling that the scrolling and enlargement / reduction of the map can be continuously and smoothly performed.

The map data of the map server 10 is mainly composed of vector data describing polygons, lines, character codes and the like.
Sends the map data of the requested mesh to the map display program 32 as vector data without converting it into bitmap data (that is, drawing a map image). Then, the map display program 32 draws a map image from the received vector data. In short, the map server 10 simply repeats the simple task of acquiring the data requested by the client from the database and returning it to the client. Thus, the load on the map server 10 is reduced, and the map server 10 can immediately return the requested map data to each client even when receiving requests from many clients. This also contributes to the effect that it is possible to obtain an operation feeling that scrolling and enlargement / reduction of the map can be continuously and smoothly performed.

FIG. 3 shows the file structure of each type of map that the map server 10 has.

As already described with reference to FIG. 2, the map server 10 has a plurality of types of maps 110 to 112, and each of the maps 110 to 112 has a file as shown in FIG. It has a configuration. As shown in FIG. 3, one type of complete map 200 has multiple layers of different data types, for example, a polygon layer 210,
It is divided into a line layer 220 and a character layer 230.
The polygon layer 210 is a collection of polygon data representing, for example, buildings and sites. Line layer 220
Is a collection of line data representing, for example, roads, railways, and rivers. The character layer 230 is a collection of character code strings representing, for example, place names and building names, and data of symbol marks such as icons and map symbols.

As described above, the entire area covered by the map is divided into a number of meshes subdivided in the latitude and longitude directions. Therefore, the polygon layer 210, the line layer 220, and the character layer 230 are each divided into data 211, 221, and 231 for each mesh. Then, data of one mesh of one layer is configured as one file.

Each mesh is assigned a mesh number corresponding to the position coordinates of the mesh on the entire map. As shown in FIG. 3, the mesh number of each mesh is represented by a coordinate value (longitudinal mesh number) Xi in the longitude direction.
And the coordinate value in the latitude direction (mesh number in the latitude direction) Yj
(Xi, Yj). Then, as shown in FIG. 3, polygon files 211, 211,... For each mesh included in the polygon layer 210, line files 221 and 2 for each mesh included in the line layer 220.
, And character files 231, 231,... For each mesh included in the character layer 230 have the same file name “XiYj” as the mesh number (Xi, Yj) of each mesh. Therefore, when map data of a certain mesh is desired, if the mesh number of the mesh (that is, the coordinate values in the latitude and longitude directions) is known, the mesh number represents the file name of the map data that is desired. . Accordingly, when the map display program 32 determines whether or not the mesh is necessary for the display range desired by the user and requests the map server 10 for the data of the mesh, the file name to be requested is immediately determined from the mesh number. be able to.

As shown in FIG. 3, in this embodiment (although this need not be the case), the polygon layer 21
0, the line layer 220 and the character layer 230 are respectively
The directories are stored in different directories in the map database 11, for example, a polygon layer directory 121, a line layer directory 122, and a character layer directory 123.

FIG. 4 shows the map database 1 shown in FIG.
1 shows the internal hierarchical structure of each of the directories 121 to 123 for each layer.

As described above, the size of one mesh is set to be small enough that one HTTP session can be completed in a short time without giving the user the feeling of waiting. Therefore, the entire area of the map is divided into a huge number of meshes. If a huge number of mesh files are simply stored in parallel in one directory, when a request for a certain file arrives, it takes a very long time to search for that file. Therefore, in this embodiment, a huge number of mesh files are managed in a directory having a hierarchical structure as shown in FIG.

That is, continuous position coordinates (ie, mesh numbers, ie, file names) as shown in FIG.
8 × 8 array of 64 mesh files 13
Are grouped into one group, and a directory (hereinafter, referred to as a “folder”) one level higher (second level) shown in FIG.
., 132, 132,... The folder name (directory name) of each folder 132 shown in FIG. 4B is the longitude component "Xi" of the file name "XiYj" of the 64 mesh files 131, 131,... Stored in each folder. The name expressed by the quotient obtained by dividing the latitude component “Yj” by the number of files “8” in the longitude direction and the latitude direction, respectively,

[0027]

(Equation 1) It has become. Therefore, each folder 13 in the second hierarchy
The folder name of 2 can be said to correspond to the position coordinates of the 8 × 8 mesh area covered by the 64 mesh files stored in each folder 132.

Then, 64 second 8 × 8 arrays having continuous folder names as shown in FIG. 4B (that is, position coordinates of the 8 × 8 mesh area shown in FIG. 4C). The folders 132, 132,...
The folder 13 one level higher (first level) shown in FIG.
3, 133,.... And FIG.
The folder name (directory name) of each folder 133 shown in (A) is the longitude component “X” of the folder names of the 64 folders 132, 132,... Stored in each folder 133.
i / 8 ”and the latitude component“ Yj / 8 ”divided by the number of folders“ 8 ”in the longitude and latitude directions, respectively,
I mean

[0029]

(Equation 2) It has become. Therefore, each folder 13 in the first hierarchy
The folder name of 3 is equivalent to the position coordinates of a 64 × 64 mesh area covered by 8 × 8 folders (that is, 64 × 64 mesh files) of the second hierarchy stored in each folder 133. be able to.

Further, 64 first-level folders 1 of an 8 × 8 array having continuous folder names (ie, position coordinates of a 64 × 64 mesh area) as shown in FIG.
Are grouped into a group, and a directory of a higher hierarchy (not shown) (for a polygon layer, for example, the polygon layer directory 121 shown in FIG. 3).
It is stored in.

In this embodiment, FIGS.
As shown in (C), by using a directory having a three-layer structure and managing 64 files or folders in one directory, a total of 64 × 64 × 64 = about 2
60,000 mesh files can be managed.
However, this is only an example, and the number of layers may be further increased as the number of meshes further increases. The reason that 64 files or folders are managed in one directory is the OS environment of Microsoft Corporation in the United States.
This is because when operating the map server 10 in a Windows environment (a high search speed is obtained when the number of files or folders in one directory is less than 100), 64 are determined to be easy to handle. , Is just one example.

What is important in the hierarchical directory shown in FIG. 4 is that the name of each hierarchical directory can be easily calculated from the file name of a specific mesh, which is the final search object. It is. That is, "X
When a file named "iYj" is desired, the folder name of a higher-level folder is easily determined by dividing the longitude component Xi and the latitude component Yj of the file name "XiYj" by 8, and arranging them. The path to the desired mesh file is

[0033]

(Equation 3) It is easily determined. By the way, if it is an n-level directory, the path to the target file is

[0034]

(Equation 4) So, it is easily determined by calculation. Note that the above calculation method of dividing the longitude component Xi and the latitude component Yj of the file name “XiYj” by 8 is merely an example,
Another calculation method may be adopted.

Regardless of the calculation method used, the fact that the path to the target file can be calculated by a predetermined numerical operation from the file name of the target mesh means that the file name of each mesh is the mesh number (position coordinates) of that mesh. In combination with the above-mentioned feature, the time required for the map display program 32 to request the map server 10 for a mesh file required for display is greatly simplified, which contributes to speeding up the map display. .

FIG. 5 shows a functional configuration of the map display program 32.

As shown in FIG. 5, the map display program 3
2 has a display unit 320 and a downloader 322. The main function of the display unit 320 is to determine a range to be displayed on the map in response to a user's operation of scrolling or enlarging or reducing the map using a mouse or the like, and to specify a file name of a mesh (mesh number) required for the display range. ), Requesting the download of the mesh file from the downloader 322, and drawing the map image to be displayed from the vector data included in the mesh file acquired from the downloader 322. The main role of the downloader 322 is to receive a file request from the display unit 320,
That is, the requested file is downloaded from the map server 10.

The display unit 320 has a memory cache 321 for storing data of files acquired in the past in a memory in a priority order according to a recent access frequency or the like. The downloader 326 downloads a download request list 325 listing the file names (paths to the files in the map server 10) of the files to be downloaded (the display unit 320 deletes the file names in this list at any time). A download flag 326 for notifying the display unit 320 of whether or not a new file has been downloaded; and a plurality of HTTP session threads 324A to 324D for performing each HTTP session when downloading each file.
(In the illustrated example, there are four threads, but the number is variable.) And a disk cache 323 for storing downloaded files in a large-capacity nonvolatile storage such as a hard disk drive. I have.

FIG. 6 shows a flow of the operation of the display section 320.

When the user performs an operation to change the display range of the map, such as scrolling or enlarging or reducing the map, using a mouse or the like (step S1), the display unit 320 performs the following operation in response to the operation. That is, all the file names described in the download request list 325 are deleted (S2), the download flag 326 is reset (S4), and a new display range after the change is determined, and the display range is determined. The file name (mesh number) of the mesh required for the range is determined (S5). In step S5, the display unit 320 determines the optimal scale as the scale of the map to be displayed in the display range based on the display magnification determined by the scaling operation (for example, a large scale if the display magnification is large,
Decide the file name required for the new display range for the map of the optimal scale, and determine the file of the optimal scale determined here. File "). In addition, each of the smaller scales (ie, a larger denominator) than the optimal scale is used to provide a temporary alternate display when the required file of the optimal scale is not immediately available (ie, performing the progressive display described above). Also for the map of (1), the file name of the mesh that overlaps the new display range is determined (the map file of a smaller scale for this alternative display is hereinafter referred to as “alternative file”).

Subsequently, the display unit 320 draws and displays a map image in the new display range in the order of the polygon layer, then the line layer, and finally the character layer.
The following processing is entered.

First, at the stage where the display of the polygon layer is not completed (NO in S6), the file of the polygon layer having the file name (mesh number) determined in step S5 is read from the memory cache 321. Search (S9). At this time, for each mesh, first, the necessary file of the optimal scale is searched. If there is no such file, an alternative file of one step smaller scale is searched.
Further, an alternative file of one step smaller scale is searched. in this way,
The file with the optimum scale is searched for first, and if there is not, the alternative file with smaller scale is searched step by step.
If a target file (necessary file or alternative file) is found in the memory cache 321 (Y in S9)
ES), a polygon map image is drawn from the vector data of the file and displayed in the corresponding mesh area on the display screen (S10). At this time, if an attempt is made to display a larger-scale map image where a smaller-scale map image has already been displayed in an alternative manner, the previously-displayed smaller-scale map image is deleted. Therefore, a larger scale map image is newly displayed.

If all the necessary files are found in the memory cache 321 (NO in S11), the display of the map of the polygon layer is completed. Next, unless there is a change in the display range (NO in S17), not yet. In order to draw and display the map of the completed line layer (NO in S7), the process proceeds to the above-described step S9 and subsequent steps. As for the line layer, if all the necessary files are found from the memory cache 321 (NO in S11), then, unless there is a change in the display range (NO in S17), the drawing of the map of the character layer which has not been completed is executed. To perform the display (NO in S8), the process proceeds to the above-described step S9 and subsequent steps. When the map image of the line layer is displayed next when the map image of the polygon layer is already displayed, or when the map image of the character layer is further displayed, a map image of a smaller scale is alternately displayed. Unlike the case where a large scale map image is displayed, the map image of the line layer is displayed on top of the already displayed polygon layer map image without erasing it, and the character Display the map image of the layer.

On the other hand, when displaying the map of the polygon layer, if at least one required file cannot be found from the memory cache 321 (S1).
1) (YES at 1), the display unit 320 next displays the memory cache 3 which is the missing required file and a substitute file for the missing required file.
The file not found from the file 21 (the missing required file and the substitute file are hereinafter collectively referred to as "missing file") is requested to the downloader 322 (S12). Also at this time, the display unit 320 first requests the necessary file of the optimal scale with the highest priority, and then requests the alternative file of a smaller scale step by step.

As will be described later, the downloader 322
When a request for a missing file is received from the display unit 320, the required file is first obtained in the requested order (that is, as in the case where the display unit 320 searches the memory cache, and if the file is not found, the required file is gradually reduced). For each missing file in disk cache 3)
23, if found, displays the path to the file found in the disk cache 323 in the display unit 3.
20. If no file is found, a response indicating that there is no file is returned to the display unit 320. When the display unit 320 receives the path to the file found in the disk cache 323 from the downloader 322 (YE in S13)
S), the file is read from the disk cache 323 using the path and the memory cache 321 is read.
(S14), and a polygon map image is drawn from the vector data of the file and displayed in the corresponding mesh area on the display screen (S15).
As described above, when an attempt is made to display a map image of a larger scale where a map image of a smaller scale has already been displayed in an alternative manner, the map image of the smaller scale displayed in the alternative is displayed first. The map image is deleted and a larger scale map image is newly displayed.

If all the necessary files are found in the disk cache 323 (NO in S16), the display of the map of the polygon layer is completed. Next, unless there is a change in the display range (NO in S17), the description is already given. Processing for drawing and displaying a map of the line layer in the same manner as above (S9 and subsequent steps)
to go into. As for the line layer, if all necessary files are found from the disk cache 323 (N in S16)
O) Since the display of the map of the line layer is completed, next, as long as there is no change in the display range (NO in S17), the process similarly draws and displays the map of the character layer (S9 and subsequent steps). As described above, when the map image of the polygon layer is already displayed, the next time the map image of the line layer is displayed, or when the map image of the character layer is further displayed, the map image of a smaller scale is used. Unlike displaying a large-scale map image depending on where the alternative image was displayed, the map image of the line layer is displayed on top of the already displayed polygon layer map image without erasing it, Further, the map image of the character layer is displayed on top of it.

In this way, if all the necessary files of all the layers exist in the memory cache 321 or the disk cache 323, the display of the map of the new display range is completed instantly. If the display of the map in the new display range is completed (YES in S8), the process returns to the beginning.

On the other hand, when a file lacking the polygon layer is requested to the downloader 322, the downloader 32
If there is at least one required file for which a response indicating that there is no file is returned from 2 (YES in S16), the processing of the display unit 320 returns to the beginning. Then, the display unit 320
Waits for the download flag 326 to be set (S2) unless there is a change in the display range (NO in S1). As will be described later, when the downloader 322 returns an answer indicating that there is no file for a certain file, the downloader 322 starts the work of downloading the file from the map server 10, and when the download of the file is completed, the file is downloaded to the disk. The contents are stored in the cache 323, and the download flag 326 is set. When it is determined that the download flag 326 has been set (YES in S2), the display unit 320 repeats the processing of step S3 and subsequent steps similar to those performed when the display range has changed. That is, all the file names in the download request list 325 are deleted (S2), the download flag 326 is reset (S4), the display range is calculated again, and the mesh file name required for the display range is calculated. (Mesh number)
Is determined (S5), and the process from step S9 for acquiring a file in the order of the polygon layer, the line layer, and the character layer and drawing and displaying the map image is repeated. As a result, the display unit 320 draws and displays the same map image again for meshes that have already been drawn and displayed, and for meshes for which files have been downloaded, The read file is read from the disk cache 323, a map image is drawn, and displayed in the mesh area.

Each time one missing file is downloaded, the display unit 320 repeats the processing from step S3, so that the display area on the display screen approaches completion one mesh at a time. When the map image of the entire display area on the display screen is completed (YE in S8)
S), the display unit 320 returns to the first step S1, waits for the display range to be changed by the user, and if changed, repeats the processing from step S3 onward.

Also, if the display range is changed by the user before the map image of the entire display area on the display screen is completed (YES in S17), the display unit 320
Repeats the processing of step S3 and subsequent steps again.

FIG. 7 shows a flow of the operation of the downloader 322.

As shown in FIG. 7, the downloader 322
Receives a file request from the display unit 320 (S2
1) First, the requested file is searched from the disk cache 323 (S22). If the target file is found from the disk cache 323 (S22
YES), the downloader 322 notifies the display unit 320 of the path of the file in the disk cache 323 (S23). If all the files requested from the display unit 320 are found from the disk cache 323 and their paths can be notified to the display unit 320 (NO in S24), the downloader 322 returns to the first step S21, and returns to the first step S21. Wait for a file request from 320 again.

On the other hand, if any of the files requested from the display unit 320 is not found in the disk cache 323 (YES in S24), the downloader 322 displays that there is no file for the missing file. In addition to the notification to the section 320 (S25), the file name of the file that was not found (including the path to the file in the map server 10) is written in the download request list 325 (S2).
6). At this time, download request list 3
25 is displayed on the display unit 320 in FIG.
Since all the file names written in the past have been erased by the processing of step S3, only the file names of the files not found at this time are written. At this time, the downloader 322 preferentially writes, on the download request list 325, a file of a smaller scale map among the files that were not found (that is, a file of a smaller scale is written closer to the top of the list). ).

Subsequently, the downloader 322 changes the file names written in the download request list 325 to the idle state in order from the top of the list 325 (that is, preferentially from the smaller scale map file). Certain HTTP session threads 324A-324
Assigned to D (S28). HTTP session
The threads 324A to 324D execute an HTTP session with the map server 10 as soon as the file names are assigned, and download the assigned files from the map server 10. HTTP session thread 3 first from smaller scale map file
As we assigned to 24A-324D, download,
Complete with smaller scale map files first.

Each time the download of an individual file is completed (Yes in S29), the downloader 322 deletes the file name of the file from the download request list 325 (S30) and stores the file in the disk cache 323. (S31), and
The download flag 326 is set (S32). Thereafter, the downloader 322 returns to the first step S21 and waits for a file request from the display unit 320 again. When the download flag 326 is set, the display unit 320 issues a file request again as described above,
Downloaded file to disk cache 3
23, and draws and displays the map image.

The display unit 320 and the downloader 322 described above
In summary, the downloader 322 simply repeats the process of downloading the missing file. Further, the display unit 320 simply tries to obtain all the files necessary for the display range every time a change in the display range or the completion of downloading the file occurs, and simplifies the process of drawing the map using only the obtained files. Just repeat. Every time the display range changes or the file download is completed,
There is a seemingly useless duplication of obtaining all the necessary files, including already drawn files, and redrawing from the beginning, but in return, which files have been drawn, It is not necessary to determine whether or not rendering is completed, and to perform a troublesome determination process of selectively rendering only undrawn files. In addition, the display unit 320 and the downloader 322 operate asynchronously, and do not perform a troublesome synchronous process such as adjusting the operation timing of both. As a result, a map image can be displayed at a high speed.

In addition, since the drawing is performed by the client computer 30, the burden of drawing on the map server 10 is not imposed. This also speeds up the response of the map server 10 and contributes to the high-speed display of the map image.

In addition, instead of trying to complete the map image that is ultimately desired at once, a polygon layer,
A progressive display method of geographic elements with different appearances, displaying map images sequentially in the order of line layer and character layer, and downloading a smaller scale map file first and displaying it first By using a progressive display method of map images of different scales (that is, an alternative display using a smaller scale map when the map of the optimum scale is not at hand), a delay in map display due to download time is provided to the user. It is possible to realize a continuous and smooth scrolling operation and an operation feeling of enlargement / reduction without making the user feel substantial.

FIG. 8 shows an example of the progressive display.

It is assumed that the user scrolls the map from a state in which a large-scale map of a certain area is displayed as shown in FIG. Then, a complete large-scale map of the scroll destination area is finally displayed as shown in FIG. 8 (D), but until the final screen of FIG. 8 (D) is reached. 8 (B) and (C) are sequentially displayed.

The screen of FIG. 8B is a screen immediately after scrolling, and the broken lines in the figure indicate mesh boundaries. In the screen immediately after this scroll, one mesh 41
For only, since the file of the polygon layer of the large-scale map has already been in the cache, the polygon image of the large-scale map is displayed. The remaining three meshes 42 ~
Regarding 44, since the large-scale map polygon layer file is still being downloaded, no large-scale map image is displayed at all. However, since the medium-scale map file was in the cache, the medium-scale map file is not displayed. The polygon images of the large buildings 431 and 441 on the map are displayed as alternatives.

After a short wait, the remaining three meshes 42-4
With respect to 4, the download of the polygon layer file of the large-scale map is completed, and the screen shown in FIG. 8C is displayed. On this screen, the display of the polygon layer of the large-scale map has been completed, but the display of the next line layer has only been completed for one mesh 41 at the upper right. For the remaining three meshes 42 to 44, since the line file of the large-scale map is still being downloaded, no image of the line layer of the large-scale map is displayed at all, but the file of the medium-scale map is not displayed. Is in the cache (or has been downloaded earlier), so the main roads 43 on the middle scale map
2,433 line images are alternately displayed.

After waiting a little more, the files of all the layers of the large-scale map are completed, and the final screen as shown in FIG. 8D is completed (however, in the figure, the image of the character layer is not shown). Is).

According to the prior art, when scrolling is performed from the state of FIG. 8A, a final screen as shown in FIG. 8D is created and transmitted on the map server side. After waiting for a long time after
The operation is switched from (A) to FIG. 8 (D) at once.
On the other hand, in the present embodiment, when a scroll operation is performed, a screen as shown in FIG. 8B is immediately displayed, and the screen is gradually completed to the final screen in FIG. 8D. It is possible to have a real feeling that the map display has been started immediately, and it is possible to immediately judge where the scroll destination is, so that a continuous scroll feeling can be obtained (same for enlargement and reduction). In addition, since a polygon image of a building or the like is particularly displayed first, the user can easily grasp the map immediately.

Further, even when an incomplete image as shown in FIG. 8B is displayed, the user can know which region it is, so that the user can determine whether or not to scroll further. You can make immediate decisions and, if necessary, continue to move forward without stopping scrolling.

FIG. 9 shows another embodiment of the present invention in which a plurality of map servers are provided to distribute the load.

A plurality of map servers 50, 50,... Are connected to a communication network such as the Internet 60, and a large number of client computers 70, 70,.
Can access any of the plurality of map servers 50, 50,.... Each of the plurality of map servers 50, 50,... Has a map database 51, 51,.

FIG. 10 shows a client computer 70.
Shows a method for requesting a plurality of map servers 50, 50,... From a plurality of map servers 50 for a mesh file required for a display range desired by the user.

As shown in FIG. 10A, in principle, each client computer 70 stores a file of a plurality of meshes 81, 81,.
Instead of requesting one map server 50, the first mesh is sent to the A server, the next mesh is sent to the B server, the next mesh is sent to the C server, and so on, and a plurality of files are sent to the plurality of servers 50, 50. , ... are almost equally distributed and requested. As a result, the load is evenly distributed among the plurality of servers 50, 50,. Also, since all of the plurality of servers 50, 50,... Have the same map data,
Maintenance of 0,... Is also easy.

If a plurality of servers 50, 50,
It is assumed that a failure has occurred in any one of..., For example, the C server. In this case, each client computer 70
Knowing that a normal response is not returned from the C server,
As shown in FIG. 10B, the remaining normal A servers and B
Requests the server to distribute files evenly.
As described above, all of the plurality of servers 50, 50,... Have the same map data. Therefore, even if a failure occurs in some of the servers, the other servers can take over. .

The form of load distribution by a plurality of servers includes:
Various things other than the above can be adopted. For example, the server may be divided for each region. For example, one or more servers are in charge of the metropolitan area with a lot of access, and another one or more servers are in charge of the remaining area.
Alternatively, the servers may be divided according to maps of different scales.
For example, one or more servers are in charge of a large-scale map with a large amount of data, and another one or more servers are in charge of the remaining scale maps. Further, the server may be divided for each layer.

The embodiments of the present invention have been described above. These embodiments are merely examples for describing the present invention, and are not intended to limit the scope of the present invention to only the above embodiments. Therefore, the present invention can be implemented in various modes other than the above-described embodiment. For example, in the above embodiment, the data of each mesh of each layer of polygons, lines, and characters is one file, but this is not always necessary. The polygon, line, and character layers are further divided into a plurality of sublayers (for example, the line layer is divided into sublayers such as a national road layer, a local road layer, a railway layer, and a river layer). May be a single file. Further, in the above embodiment, the entire area covered by each map data is subdivided into small-area meshes, and the entire map data is fragmented into data in units of meshes, but this is not always necessary. . Instead of fragmenting for each mesh, or in combination with fragmentation for each mesh, individual geographic elements (for example, each road, each railroad track, each river, each building, each site, each map) constituting a map (Symbols, icons, etc.).

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic overall configuration of an embodiment of an image display system according to the present invention.

FIG. 2 is a view for explaining the types of maps possessed by the map server and the order in which a map display program in a client computer requests map data from the map server;

FIG. 3 is an explanatory diagram showing a file configuration of each type of map possessed by the map server 10;

FIG. 4 is an explanatory diagram showing a hierarchical structure inside each of directories 121 to 123 for each layer in the map database 11 shown in FIG. 3;

FIG. 5 is a block diagram showing a functional configuration of a map display program 32.

FIG. 6 is a flowchart of an operation of a display unit 320.

FIG. 7 is a flowchart of the operation of the downloader 322.

FIG. 8 is a transition diagram of a screen showing an example of a progressive display.

FIG. 9 is a block diagram showing an embodiment in which the load is distributed among a plurality of map servers.

FIG. 10 is an explanatory diagram showing a method when the client computer requests a plurality of map servers 50, 50,... For a mesh file necessary for a display range desired by the user.

[Explanation of symbols]

10 Map Server 20 Internet 30 Client Computer 31 Client Program 32 Map Display Program 34 Mouse 131 Mesh File 132 Second Hierarchy Folder 133 First Hierarchy Folder 211, 221, 231 Mesh

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09B 29/00 G09B 29/00 A (72) Inventor Daisuke Tabuchi 4-20-3 Ebisu, Ebisu, Shibuya-ku, Tokyo Ebisu Garden Place Tower 13th floor Dreamte Knology's Co., Ltd. (72) Inventor Yasuo Hyugano 4-20-3 Ebisu, Shibuya-ku, Tokyo Ebisu Garden Place Tower 13th floor Dreamte Knolls Co., Ltd. (72) Inventor Ichiro Nakajima Ebisu Shibuya-ku, Tokyo 4-20-3 Ebisu Garden Place Tower 13th floor Dreamte Technologies Co., Ltd. F-term (reference) 2C032 HB03 HC08 HC24 HC25 HC32 5B050 AA08 BA17 CA07 CA08 EA12 FA02 FA13 FA19 GA08 5B057 AA13 AA16 BA24 BA26 CA08 CA12 CA16 CB08 CB12 CB08 CD05 C E09 CH08 CH11 CH12 CH18 5B069 AA02 CA06 CA07 DD11 LA03 5C076 AA21 AA22 BA04 CA02 CA08 CB03

Claims (15)

[Claims] 1. A system for transmitting image data from an image server to a client through a communication network and displaying an image on the client, wherein the image server stores a plurality of whole image data having different scales, The scaled whole image data is divided into a plurality of fragment image data each representing an image of a small region obtained by dividing the whole image into regions, and responds to a user operation of scrolling or enlarging or reducing the display on the client. Then, the fragment image data necessary for display is selected from a large number of fragment image data in the image server, and is transmitted from the image server to the client through a communication network. Drawing and displaying an image using fragment image data received from the image server; Display system. 2. When a plurality of pieces of fragment image data having different scales are transmitted from the image server to the client,
2. The image display system according to claim 1, wherein priority is given to transmitting the small-scale fragment image data. 3. The image display system according to claim 1, further comprising a plurality of image servers, wherein the fragment image data can be transmitted to the client from any of the plurality of image servers. 4. A method for transmitting image data from an image server to a client through a communication network and displaying an image on the client, the image server comprising: a plurality of whole image data having different scales; Storing the plurality of entire image data having a configuration in which the entire image data is divided into a plurality of fragment image data each representing an image of a small area obtained by subdividing the entire image into regions. In response to a user operation of scrolling or enlarging or reducing the display on the client, fragment image data required for display is selected from among a number of fragment image data in the image server, and the fragment image data is transmitted from the image server through a communication network. Transmitting to the client; and disconnecting the client from the image server. Displaying an image using one-sided image data. 5. The image display method according to claim 4, wherein, in the step of transmitting the fragment image data, when transmitting a plurality of fragment image data having different scales, the fragment image data having a smaller scale is transmitted preferentially. 6. An apparatus for receiving and displaying image data from an image server via a communication network, comprising:
The image server stores a plurality of whole image data of different scales, and the whole image data of each scale includes a plurality of fragment image data each representing an image of a small area obtained by subdividing the whole image into regions. Means for requesting the image server to transmit fragment image data necessary for display from among a large number of fragment image data in the image server in response to a user operation of scrolling or enlarging or reducing the display. An image display device comprising: a unit for receiving fragment image data transmitted from the image server; and a unit for displaying an image using the fragment image data received from the image server. 7. The image display apparatus according to claim 6, wherein the requesting unit gives a higher priority to the smaller-scale fragment image data when requesting a plurality of fragment image data having different scales from the image server. 8. A method for receiving and displaying image data from an image server via a communication network, the method comprising:
The image server stores a plurality of whole image data of different scales. Requesting the image server to transmit fragment image data necessary for display from among a large number of fragment image data in the image server in response to a user operation of scrolling or enlarging or reducing the display. An image display method comprising: receiving fragment image data transmitted from the image server; and displaying an image using the fragment image data received from the image server. 9. The image display method according to claim 8, wherein, in the requesting step, when a plurality of pieces of fragment image data having different scales are requested to the image server, the request is made preferentially from small-scale fragment image data. 10. A computer program which, when executed by a computer, receives and displays image data from an image server through a communication network, wherein the image server stores a plurality of whole image data having different scales. The total image data of each scale is
The whole image is divided into a plurality of fragment image data each representing an image of a small region obtained by subdividing the whole image into a plurality of fragments. In response to a user operation of scrolling or enlarging or reducing the display, a number of fragments in the image server are divided. A program segment for performing a step of requesting the image server to transmit fragment image data necessary for display from image data, and a program segment for performing a step of receiving fragment image data transmitted from the image server A computer program for displaying an image, comprising: a program segment for performing a step of displaying an image using fragment image data received from the image server. 11. The program segment for performing the requesting step, when requesting a plurality of fragment image data of different scales from the image server, preferentially requests the smaller-scale fragment image data. Computer programs. 12. An image server for transmitting image data to a client through a communication network, wherein a plurality of whole image data having different scales is obtained by subdividing the whole image into regions. Storage means for storing the plurality of whole image data having a structure of being divided into a plurality of fragment image data each representing an image of a small area; and storing the fragment image data necessary for display on a client. Transmitting means for selecting and transmitting from among a large number of fragment image data in the means. 13. When transmitting a plurality of pieces of fragment image data having different scales to the client, the transmitting means transmits the pieces of fragment image data having a smaller scale preferentially.
Image server as described. 14. A method for transmitting image data from an image server to a client via a communication network, wherein the plurality of whole image data having different scales includes: Storing the plurality of whole image data having a structure of being divided into a plurality of fragment image data each representing an image of a subdivided small area; and storing fragment image data necessary for display on a client. And transmitting the selected fragment image data from a large number of fragment image data. 15. The image data transmitting method according to claim 15, wherein, in the transmitting step, when transmitting a plurality of fragment image data having different scales to the client, the fragment image data having a smaller scale is preferentially transmitted.