JP4743820B2 - Image display apparatus and program - Google Patents

Description

  The present invention relates to an image display apparatus and method for quickly displaying an enlarged / reduced image according to an instruction from an apparatus operator, such as a copying machine, and more particularly to an image display apparatus and an image display for displaying an enlarged / reduced image. It is about the method.

  2. Description of the Related Art Conventionally, in an apparatus capable of displaying an image processing result, such as a copying machine, an image to be displayed is generally compressed and stored in a storage device such as a hard disk connected to a memory or a PCI bus. FIG. 9 shows a configuration example of the conventional technique, and FIG.

  As shown in FIG. 9, a conventional image processing apparatus includes a main processing unit (CPU) 101, a main memory 102, an LCDC 103 for displaying image processing results, an LCD display 107, a color reduction processing unit 106 for performing color reduction processing, a zoom / A scroll processing unit 105, a JPEG decoder 104, a PCI bus controller 108, and the like are connected to a local bus, and include a PCI bus 109 and a storage device 110 connected to the PCI bus controller 108.

  Images to be displayed on the LCD display 107 are generated from four types of JPEG image compression data of 25 dpi, 50 dpi, 100 dpi, and 200 dpi stored in the storage device 110. These images are divided into tiles of 32 pixels × 32 pixels, and JPEG compression is performed for each tile. The resolution (image resolution) of the image data represents the pixel density when the image size (length) is constant. For example, a 200 dpi image is image data to be output at 200 pixels per inch. In other words, a 200 dpi image refers to image data that is assumed to be output on a medium having a display resolution of 200 dpi. When image data with different resolutions is displayed as it is on a display device having a constant display resolution for a single image, the difference in image resolution appears as a difference in image size. For example, the size (length) of an image having each image resolution of 25 dpi, 50 dpi, and 100 dpi is 1/8, 1/4, and 1/2 in length ratio, with 200 dpi being 1, respectively. When displaying an image of each size according to the size of the original image before compression, for example, if the image resolution of the original image is 200 dpi, each image resolution of 25 dpi, 50 dpi, and 100 dpi is 8 times, 4x and 2x enlarged images are displayed. In this case, the enlarged images have the same size, and appear to be displayed at the respective resolutions.

On the LCD display 107, an image with an image resolution designated by the operator of the apparatus is displayed. Displayed image data is displayed using the image data if the image resolution matches the image resolution of the image data stored in the storage device 110 after JPEG compression. If they do not match, image data having the designated image resolution is generated and displayed. The image data with the designated image resolution is generated from the image data with the image resolution immediately above and below the designated image resolution among the image data compressed with JPEG. If there is no image data of the image resolution immediately above or directly below, it is generated using the image data that exists. That is, in the above example, it is generated from JPEG image compression data of four types of image resolution stored in the storage device 110. (See Patent Document 1 etc.)
Here, the processing of FIG. 10 will be described by taking as an example a case where an image resolution of 150 dpi is instructed. When the image resolution of the image to be displayed is instructed, the JPEG decoder 104 is necessary to display the entire image from the compressed image data of 100 dpi immediately below 150 dpi and the compressed JPEG image data of 200 dpi immediately above. The JPEG compressed data of the partial tile is read from the storage device 110 (S1001). The read compressed image data is expanded, and the expanded image data is written to the main memory 102 (S1002). The zoom / scroll processing unit 105 generates 150 dpi image data from the expanded 100 dpi and 200 dpi image data, and writes the image data to the main memory 102 (S1003). Then, color reduction processing is performed on the image data generated in accordance with the display capability or the like (S1004), and the generated image data is displayed on the LCD display 107 (1005).

FIG. 7 shows an example of the scroll process. When a scroll operation occurs while displaying a zoom image 701 of 150 dpi, the JPEG decoder 104 stores data (tiles) to be added in the scroll direction, 100 dpi and 200 dpi compressed image data stored in the storage device 110. The data read and decompressed is written to the main memory 102. The zoom / scroll processing unit 105 generates a 150 dpi zoom image from the decompressed data and writes it to the main memory 102. The CPU 101 adds the generated image to the portion that is displayed even after scrolling, and writes a new display image 702 to the main memory 102. Then, the image displayed on the LCD display 107 is switched to a newly generated display image to make it appear as if scrolling has occurred.
JP 2003-202855 A

  In the conventional method, after the operator designates the resolution, the necessary JPEG image compression data is read and an image having the designated resolution is generated. Therefore, it takes time until the image is displayed after an instruction from the operator of the apparatus is given. There was a problem that it took. On the other hand, when the display area includes text, the operator of the apparatus often displays the image processing result in a size (that is, image resolution) that allows the text to be read without difficulty. For example, small characters rarely continue to be displayed at a size that allows the entire A4 version document to be displayed, and conversely large characters such as headline characters are rarely enlarged and displayed. For this reason, the operator gives an instruction to enlarge or reduce the image according to the display size of the text. However, due to the above-described problem, the response until the image is displayed in response to the instruction to enlarge or reduce the image is high. It was bad.

  The present invention has been made in view of the above conventional example, and is necessary for detecting text characters in an image, recognizing the size of the character, and enlarging or reducing the image so that the size of the character is substantially constant. To provide an image display device and an image display device with good responsiveness that can quickly display an image of a size specified by an operator according to an instruction by prefetching compressed JPEG image data with a high resolution With the goal.

  In order to achieve the above object, the present invention comprises the following arrangement.

Storage means for storing image data composed of tiles having a predetermined resolution and different resolutions corresponding to one image;
Display means for displaying an image based on the image data read from the storage means;
Recognizing means for recognizing the size of a character included in the image displayed by the display means before the change of the zoom magnification after display is performed ;
Calculation means for calculating an image resolution for causing the display means to display the character in a predetermined size from the size of the character recognized by the recognition means before the change of the zoom magnification after display is performed ;
The image data of at least one kind of resolution among the image data composed of tiles having a predetermined pixel size having different resolutions according to the image resolution is stored before the zoom magnification after display is designated. Reading means for reading from the means;
Determining means for determining whether image data for obtaining image data having a resolution according to the zoom magnification designated for change is read by the reading means;
The determination means requires image data of two kinds of resolutions as image data for obtaining image data of resolution according to the zoom magnification designated for change, and the read image data is the 2 When it is determined that only one of the two types of resolution image data is read, the remaining resolution image data of the two types of image data is read, and the read image data and the remaining resolution of the read resolution are read. Image data having an intermediate resolution of the image data is generated, and the image data having two different resolutions as the image data for obtaining the image data having the resolution according to the zoom magnification designated by the change is read by the determination unit. If it is determined that the previously read by means, said two different resolutions two different from the image data of the resolution image Day An image display device provided with a zoom processing means for generating an intermediate resolution image data,
The readout means gives priority to the image areas that can be displayed by the display means in order from the upper left to the lower right of the image area with reference to the center of the image area displayed by the display means. Then, image data composed of tiles having a predetermined pixel size is read from the storage means in units of tiles having a predetermined pixel size according to the priority.

  According to the present invention, image data having a resolution necessary for enlarging or reducing an image so that characters in the displayed image have a certain size are read in advance prior to an instruction to enlarge or reduce. Accordingly, the display response to an enlargement or reduction instruction can be improved. For this reason, the operability and productivity of the image display apparatus can be improved.

<Device configuration>
FIG. 1 is a block diagram showing an example of the configuration of an image processing apparatus according to an embodiment of the present invention. As shown in FIG. 1, in this image processing apparatus, a main arithmetic unit (CPU) 301, a main memory 302, an LCD controller (LCDC) 303 for controlling an LCD display 307, and generated image data are displayed as images. An LCD display (LCD) 307, a color reduction processing unit 306 that performs color reduction processing, a zoom / scroll processing unit 305, a JPEG decoder 304, and a PCI bus controller 308 are connected by a local bus. A storage device 310 for image data such as a hard disk or a nonvolatile memory is connected to the PCI bus 309.

  Here, the CPU 301 executes a program of the procedure shown in FIG. 4, FIG. 6, FIG. 11, etc. stored in the memory 302 to control the entire apparatus. For example, by executing a program, an instruction is given to each processing unit in response to an instruction input from an operator of the apparatus. In addition to the program, the main memory 302 stores information for image processing and information necessary for displaying the image processing result. In particular, the pre-read image data is stored in the pre-read area 311. The JPEG decoder 304 expands JPEG compressed image data stored in the storage device 310. The storage device 310 stores image data compressed in a stepwise size (image resolution) in the JPEG progressive mode. The zoom / scroll processing unit 305 generates an image with the instructed resolution and performs processing associated with scrolling. The color reduction processing unit 306 performs color reduction processing (quantization processing) by error diffusion. The JPEG decoder 304, the zoom scroll processing unit 305, and the color reduction processing unit 306 can be realized by dedicated hardware or a slave CPU, and a program corresponding to each processing unit is executed by the CPU 301 for each processing unit. It can also be realized by executing it as an independent process. The storage device 310 stores JPEG compressed image data. In this embodiment, the LCD 307 is a color display with 8 bits input per pixel.

  FIG. 2 shows data stored in the main memory 302. An image data prefetch area 311 is secured in the main memory 302. In the main memory 302, a zoom image work area 203 for storing a zoom image generated by the zoom / scroll processing unit 305, a zoom image work area 204, and a JPEG expansion work area 205 for storing expansion data by the JPEG decoder 304 are stored. An LCD work area 206 and an LCD work area 207 for storing data used for LCD display are prepared.

  FIG. 3 shows data stored in the storage device 310. The storage device 310 stores image data 3002 to 3005 having four kinds of image resolutions of 25 dpi, 50 dpi, 100 dpi, and 200 dpi for one image 3000. Also included is management information 3001 for storing file names, attribute values, and the like. The image data of each image resolution is divided into 32 × 32 pixel tiles, and each tile is stored after being JPEG compressed. For example, the image data can be captured by a file function in a copying machine, and can be captured from an image input device such as a connected scanner digital camera in a general-purpose computer. JPEG compression may be performed by an input device, or captured image data may be JPEG compressed by this image processing apparatus.

<Image display processing>
FIG. 11 is a processing procedure executed by the CPU 301 in order to display a designated image at a designated image resolution (ie, size). This procedure is executed when an image and an image resolution are designated and display execution is instructed. First, image data having an image resolution corresponding to the designated size is read from the storage device 310, decompressed, and stored in the zoom image work area 203 of the memory 302 (step S1101). If image data of two types of image resolution is necessary for the zoom process, the expanded image data is similarly stored in the zoom image work area 203. The JPEG decompression work area 205 is used for the decompression process. If there is room in the memory, the image data may be read and expanded for the entire image. However, if there is no room in the memory, the image is read and expanded centering on the displayed area.

  Next, the read image data is subjected to zoom processing (step S1102). As described in the section of the prior art, if necessary, image data having designated image resolution is generated from image data having two types of image resolution. Then, in accordance with the display capability of the LCD display 307, image data color reduction processing, that is, quantization processing is performed (step S1103). FIG. 8 shows an example of the format of image data. In the example of FIG. 8, a case where one word is composed of 4 octets is illustrated. Image data 801 is image data before color reduction processing, and is composed of 24 bits of 8 bits for each color of RGB (red green blue) per pixel. The image data 892 is image data after color reduction processing, and one pixel is composed of 8 bits of R 3 bits, G 3 bits, and B 2 bits. In the subtractive color processing, for example, the lower 5 bits are rounded down for R and G, and the lower 6 bits are rounded down for B. The reduced color image data is stored in an unused LCD work area (for example, LCD work area 206) in the memory 302.

  Next, the reduced color image data is read from the LCD work area 206 on the main memory 302, and the image data is output to the LCDC 303. The LCDC 303 displays an image corresponding to the image data on the LCD 307.

<Image data prefetch processing>
After the image is displayed in this way, the image data is pre-read in the procedure shown in FIG. 4 between the processes. In FIG. 11, for convenience of explanation, it is described that the process proceeds to prefetch processing immediately after display. However, when the image processing apparatus according to the present embodiment is realized by a computer on which the multitask operating system is executed, for example, when the task of the display process in FIG. , Schedule with a lower priority than the zoom processing tasks of FIGS. By doing in this way, when the display process is not performed, the prefetch process of FIG. 4 is performed.

  The prefetching operation of the image data by the image processing apparatus of this embodiment will be described according to the processing flow of FIG. Prefetching targets image data that has a high probability of being displayed after the image is displayed in the procedure of FIG. 11 or in the procedure of FIG. 6 described later. Therefore, in FIG. 4, first, image data with a high probability of being displayed is selected, and then the selected image data is read out.

  When the zoom image is displayed on the LCD 307 by the procedure of FIG. 11 or the procedure of FIG. 6 described later, the CPU 301 recognizes the text in the image for the image data in the zoom image work area in the main memory 302. (Step S401), it is determined whether there is a character (S402). If there is a character, the size of the character is determined (step S403).

  The CPU 301 calculates an image resolution for displaying a certain number of characters in the image display area from the character size (step S404). Here, when there are a plurality of characters of different sizes in the display area, the minimum size is used as a reference. This is because it is expected that the operator will perform an operation of scaling the image until the size of the minimum size character is easily visible. The image resolution for displaying a certain number of characters in the image display area is determined in advance according to the resolution of the display medium (LCD 307 in this example). If the resolution of the LCD 307 is, for example, 100 dpi and the character size that is easy for the operator to read is, for example, about 5 millimeters (1/5 inch) square, the size of one character is 100/5 = 20 pixel square in terms of the number of pixels. Become. Therefore, the scaling factor is determined so that the minimum character recognized in the display area is 20 pixels square.

  This will be described using image resolution. Assume that the image resolution of the displayed image data is Xdpi, and the recognized minimum character size is x pixel square. If the easy-to-see character size is y (20 in the above example) pixel square, the image resolution Y at which the character size is y pixel square is Y = X × (y / x).

  Here, if the image resolution Y calculated by the CPU 301 is 170 dpi, 200 dpi and 100 dpi JPEG image compression data is designated as a prefetch target. If the image resolution calculated by the CPU 301 is 30 dpi, 50 dpi and 25 dpi JPEG image compression data is a target to be prefetched. Of course, the image resolution determined as a prefetch target (hereinafter referred to as prefetch image resolution) is stored in the memory 302 or the like and is referred to when prefetching.

  Next, a tile to be prefetched is determined from image data having the prefetched image resolution (step S405). This is because the image data is compressed and stored in tile units. The prefetch target image tile is a tile necessary for displaying an expected image after scaling in the image display area, centering on the currently displayed image area. The tiles in that area are also prioritized from the upper left tile in order to the upper right tile, and then the next lower tile is given priority from the left edge to the right edge. I can receive it. In the ranking, the upper left has a high priority, and the lower the right, the lower the priority. FIG. 5 shows an example of prioritization. In the pre-read target area 501, a priority is assigned to each tile. The priority order is represented by, for example, a table in which tile coordinates of tiles to be prefetched are arranged (hereinafter referred to as a prefetch tile table). The prefetch tile table is stored in the memory 302. Next, a method for creating a prefetch tile table will be described.

  The range of the prefetch target can be determined from the range of the currently displayed image and the image resolution of the prefetched image data if the display range of the image is constant. At that time, for example, a method of determining the prefetch range based on the center of the display area, or a method of determining based on the corner point (for example, the upper left corner) of the display area can be considered. The reference means that the point is not changed from the current display position. For example, for the entire image, the upper left corner is the origin, the coordinates of the upper left corner of the display area are (xl, yl), and the coordinates of the lower right corner are (xr, yr). If the upper left corner point of the display area is used as a reference and the scaling factor is n, the range assumed to be displayed after scaling is (xl, yl) for the upper left corner and (xl + (xr-xl) for the lower right corner. × n, yl + (yr−yl) × n).

  This coordinate value is represented by a pixel position in the image data of the image resolution to be prefetched, and tile coordinates including the pixel position are calculated. The tile coordinates are the positions of the tiles in the image expressed with coordinates in units of tiles. Further, the position on the image represented by the pixel position changes according to the image resolution. For example, when a certain position is represented by the coordinates of the number of pixels in the image data having an image resolution of 200 dpi, the position is represented by dividing each coordinate component by half in the image data having an image resolution of 100 dpi. The If the image resolution is 50 dpi, the coordinate value of the position is represented by a quarter of the pixel position at 200 dpi. For example, the position of (200, 200) in the 200 dpi image data is represented by (100, 100) in the 100 dpi image data and (50, 50) in the 50 dpi image data. Since the tile size is constant regardless of the image resolution, the quotient obtained by dividing each coordinate component of the position represented in this way by the tile size (number of pixels) becomes the coordinate component of the tile coordinate. For example, if the tile size is 32 × 32 pixels, the pixel position of (200, 200) is included in the tile at the position of (6, 6) in tile coordinates. Thus, the tile coordinates of the upper left corner tile and the lower right corner tile coordinates of the image data to be prefetched are determined. After this, create a look-ahead tile table in which the tile coordinates in the rectangular area determined by the tile coordinates of the upper left corner tile and the tile coordinates of the lower right corner are arranged in order from the upper left to the lower right, and stored in memory To do. Since the tile coordinates are arranged in the priority order in the prefetch tile table, information on the priority order is also included. The prefetch tile table is referred to during actual prefetching.

  When image data and tiles to be prefetched are determined, it is next determined whether or not there is an empty image data prefetch area 201 in the memory 302 (step S406). Do not look ahead if there is no space. Therefore, the same determination as in step S406 may be performed immediately before step S401, and the process may be terminated if there is no space.

  If there is free space in the memory, the CPU 301 causes the JPEG decoder 304 to perform a prefetch operation for image data (step S407). Specifically, when the image data prefetch area 201 in the memory 302 has a free space, the CPU 301 gives an instruction to the JPEG decoder 304, and from the prefetch image resolution image data, the priority is high according to the prefetch tile table. JPEG compressed data is read from each tile. Then, the JPEG decoder 304 performs JPEG expansion processing on the read data. Data decompressed by the JPEG decoder 304 is written to the image data prefetch area 201.

  The data written in the prefetch area 201 must be able to specify what kind of data it is. As an example, FIG. 12 shows the format of the prefetched data. The expanded image data is managed in units of tiles, and a tile coordinate 1203 is assigned to each tile. The data having the same image resolution of the same image is associated with resolution data 1202 representing the image resolution. In this way, tiles are managed for each image resolution, and image data with different image resolutions are associated with the image data file name 1201 of one image. Thus, it is possible to specify which image, which image resolution, and which part of the pre-read data. Of course, the management method is not limited to this. For example, all the prefetched tiles are connected to generate one area, and the file name, image resolution, and information indicating the generated area (in the case of a rectangular area, diagonal coordinates, etc.) Thus, the data can be managed.

  In step S409, it is determined whether there is still data to be prefetched. If there is, data is repeated from step S406.

  The pre-reading operation is data in which the image data pre-reading area 201 in the memory 302 is empty and can be pre-read while there is no change work on the image displayed on the LCD 307 such as the zoom magnification change and scrolling operation by the operator of the apparatus. As long as is left, it is continued by the CPU 301.

<Zoom processing>
Next, the zoom operation using the pre-read image data will be described according to the processing flow of FIG.

  When zoom processing is started by the operator of the apparatus, the CPU 301 determines whether or not necessary data is pre-read in the image data pre-read area 201 in the memory 302 (step S601). The image resolution and tiles of data necessary to perform image scaling and display at a designated zoom magnification can be determined in the same manner as steps S404 and S405 in FIG. The file name including necessary data is the file name of the image to be displayed. In the structure shown in FIG. 12, referring to the file name 1201, the image resolution 1202, and the tile coordinates 1203, the file name and image resolution of the data necessary for scaling and displaying the image at the designated zoom magnification. Determine whether tile coordinates are included in the prefetched data. In this way, when image data of a portion necessary for displaying on the LCD 307 by zoom processing is stored in the image data prefetch area 201 in the memory 302, it is determined that the data has been prefetched. .

  The zoom / scroll processing unit 305 uses two types of resolution data in order to display on the LCD 307 an image with a resolution specified by the operator of the apparatus. The CPU 301 performs different processing when data of two types of resolution is stored in the image data prefetch area 201 in the memory 302 and when only data of one type of resolution is stored. Therefore, it is determined whether data having the necessary resolution is available (step S607). If neither of the two types of resolution data is stored, it is determined that the data has not been prefetched, and the process branches to step S602. In this example, pre-reading data with one image resolution means that all data having that image resolution is pre-read.

  Here, as an example, it is assumed that the image resolution specified by the operator is 150 dpi. In order to generate an image with an image resolution of 150 dpi, two types of image data with an image resolution of 100 dpi and 200 dpi are required. When two types of data of 100 dpi and 200 dpi are stored in the image data prefetch area 201 in the main memory 302, the CPU 301 instructs the zoom / scroll processing unit 305 to have 100 dpi and 200 dpi in the image data prefetch area 201. 150 dpi image data is generated from the above data. The zoom / scroll processing unit 305 writes the generated image data to the zoom image area 2204, and generates a zoomed image (step S615). The prefetched data that is no longer needed is deleted from the prefetch area (step S616).

  Next, the CPU 301 gives an instruction to the color reduction processing unit 306 to execute the color reduction processing (step S617). The color reduction processing unit 306 reads an image from the zoom image work area 2204 in the main memory 302, performs color reduction processing, writes data to the LCD work area 1206 in the main memory 302, and generates an image to be displayed on the LCD 307 ( Step S618). If only one type of data is required, if it is prefetched, the process branches to step S615.

  When only one of the data, that is, only 200 dpi image data in this example is stored in the image data prefetch area 201 in the main memory 302, the CPU 301 performs 100 dpi in the storage device 310 with respect to the JPEG decoder 304. JPEG image compressed data is read (step S608). The JPEG decoder 304 decompresses the 100 dpi JPEG image compression data (step S6109), and writes the data to the JPEG decompression work area 205 secured in the main memory 302 (step S610).

The CPU 301 causes the zoom / scroll processing unit 305 to generate a 150 dpi image from the 200 dpi decompression data in the image data prefetch area 201 and the 100 dpi decompression data in the JPEG decompression work area 205. The zoom / scroll processing unit 305 writes the generated image data to the zoom image area 2204, and generates a zoomed image (step S611). The prefetched data that has become unnecessary is deleted from the prefetch area (step S612).
Next, the CPU 301 gives an instruction to the color reduction processing unit 306 to execute the color reduction processing (step S613). The color reduction processing unit 306 reads an image from the zoom image work area 2204 in the main memory 302, performs color reduction processing, writes data to the LCD work area 1206 in the main memory 302, and generates an image to be displayed on the LCD 307 ( Step S614). The LCDC 303 reads out the reduced color image from the LCD work area 1206 on the main memory 302 and displays it on the LCD 307.

  When necessary data is not stored in the image data prefetch area 201 in the main memory 302, the operation is the same as that of the conventional technique. The necessary JPEG compressed data is read from the storage device 310 (step S602), the data is expanded by the JPEG decoder 304 (step S603), and an image to be displayed by the zoom / scroll processing unit 305 is generated (step S604). The source color is selected (step S605) and displayed on the display (step S606).

[Effect of this embodiment]
As described above, the operator has a high tendency to display the number of characters that can read characters in the display area without stress and can determine the content of the text. Utilizing this tendency, the resolution (that is, a certain character size) that fits a certain number of characters in the display area is calculated, and the data required for zooming to that size is prefetched. And the zoom operation becomes fast.

[Modification 1]
In the above-described embodiment, the image resolution Y that is considered to be displayed with high probability is obtained as Y = X × (y / x). If y> x, enlargement, if y <x, reduce, and if x = y, do not scale. Here, the image resolution Y may not be set to one but may have a certain width. That is, the range is determined in advance as y1 <y2 as the character size y that is easy to visually recognize. If x <y1, the image resolution Y is obtained as Y = X × (y1 / x) to make the character size y1, and if x> y2, the image resolution Y is made to make the character size y2. Obtained as Y = X × (y2 / x). If the image resolution Y considered to be highly likely to be displayed is determined, the rest is the same as in the above embodiment. If y1 <x <y2, the currently displayed image is determined not to be prefetched because it is determined that the characters included in the image are easily visible.

  It is considered that there is an allowable range for the size of characters that are easily visible to the operator. Therefore, by avoiding the prefetching process with a certain width in this way, it is possible to use resources for other processes without performing the prefetching process that is likely to be wasted.

[Modification 2]
When an operator instructs image scaling, there are many image processing apparatuses and image processing application programs having a user interface for designating the scaling ratio as an integer multiple or a fraction of an integer. For this reason, in the present modification, the pre-read image data is also pre-determined based on the character size with a specified scaling factor having a high probability of being specified, and pre-read image data with the corresponding image resolution.

  Assume that the image resolution of the displayed image data is Xdpi, and the recognized minimum character size is x pixel square. Assume that the size of easy-to-see characters is in the range of y1 pixel square <y2 pixel square. If x <y1, the scaling factor n = roundup (y1 / x) is obtained. If x> y2, the scaling factor n = 1 / (rounddown (x / y2)) is obtained. Here, roundup and rounddown are functions indicating rounding up and rounding down of the decimal part, respectively. The obtained scaling factor n is a scaling factor that is given by an integer multiple or a fraction of an integer that is highly likely to be specified by the user to read characters included in the image. Therefore, the image resolution Y obtained by scaling the currently displayed image by n times is Y = n × X. Then, the image data necessary for generating the image data with the image resolution Y is prefetched. Thus, the procedure of the embodiment is the same except for the method of determining Y. If y1 <x <y2, the currently displayed image is determined not to be prefetched because it is determined that the characters included in the image are easily visible.

  As described above, even in a device having a user interface that performs image scaling by designating a scaling factor, an image necessary for generating an image scaled at a specified scaling factor having a high probability of being specified. The data can be read in advance, and the responsiveness when the scaling operation is actually performed can be improved.

[Modification 3]
In FIG. 6, it is determined that all necessary tiles have been prefetched when it is determined that the data with the necessary resolution has been prefetched. However, if only tiles that have not been pre-read are read during zoom processing, the pre-read data is not wasted. Therefore, only steps S608 to S614 are executed in the procedure of FIG. However, the JPEG data read from the storage device in step S608 is necessary data that has not been pre-read. By comparing the data necessary for the zoom process with the pre-read data in the manner described in step S601 in FIG. 6, the necessary data that has not been pre-read can be determined in tile units. Can read the determined tile. Then, it is expanded in step S909, and all necessary data is read out to the prefetch area. When all the necessary data is obtained in this way, the processing after step S610 is performed.

[Other Embodiments]
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), and a device (for example, a copying machine and a facsimile device) including a single device. You may apply to. Another object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or CPU) of the system or apparatus. (MPU) can also be achieved by reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code itself and the storage medium storing the program code constitute the present invention.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. A case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included. Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. This includes a case where the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

The figure showing the structure of embodiment of this invention Diagram showing information in memory Diagram showing information in the storage device The figure which shows the flow of the prefetch process of embodiment of this invention The figure which shows prioritization of the prefetch process of embodiment of this invention The figure which shows the flow of the scroll process of embodiment of this invention Diagram showing an example of scroll processing Diagram showing image format Diagram showing the configuration of the prior art Diagram showing the flow of processing in the prior art The figure which shows the procedure of image display processing The figure which shows an example of the structure of the prefetch data managed per tile

Explanation of symbols

101, 301 ... CPU
102, 302 ... main memory 103, 303 ... LCD controller 104, 304 ... JPEG decoder 105, 305 ... zoom / scroll processing unit 106, 306 ... subtractive color processing unit 107, 307 ... LCD
108, 308 PCI controller 109 309 PCI bus 110 310 Storage device 311 Prefetch area 201 Image data prefetch area 203 Zoom image work area 1
204 ... Zoom image work area 2
205 ... JPEG decompression work area 206 ... LCD work area 1
207 ... LCD work area 2

Claims (2)

Storage means for storing image data composed of tiles having a predetermined resolution and different resolutions corresponding to one image;
Display means for displaying an image based on the image data read from the storage means;
Recognizing means for recognizing the size of a character included in the image displayed by the display means before the change of the zoom magnification after display is performed ;
Calculation means for calculating an image resolution for causing the display means to display the character in a predetermined size from the size of the character recognized by the recognition means before the change of the zoom magnification after display is performed ;
The image data of at least one kind of resolution among the image data composed of tiles having a predetermined pixel size having different resolutions according to the image resolution is stored before the zoom magnification after display is designated. Reading means for reading from the means;
Determining means for determining whether image data for obtaining image data having a resolution according to the zoom magnification designated for change is read by the reading means;
The determination means requires image data of two kinds of resolutions as image data for obtaining image data of resolution according to the zoom magnification designated for change, and the read image data is the 2 When it is determined that only one of the two types of resolution image data is read, the remaining resolution image data of the two types of image data is read, and the read image data and the remaining resolution of the read resolution are read. Image data having an intermediate resolution of the image data is generated, and the image data having two different resolutions as the image data for obtaining the image data having the resolution according to the zoom magnification designated by the change is read by the determination unit. If it is determined that the previously read by means, said two different resolutions two different from the image data of the resolution image Day An image display device provided with a zoom processing means for generating an intermediate resolution image data,
The readout means gives priority to the image areas that can be displayed by the display means in order from the upper left to the lower right of the image area with reference to the center of the image area displayed by the display means. An image display device that reads out image data composed of tiles having a predetermined pixel size in units of tiles having a predetermined pixel size according to the priority from the storage unit. Storage means for storing image data composed of tiles having a predetermined resolution and different resolutions corresponding to one image;
Display means for displaying an image based on the image data read from the storage means;
Recognizing means for recognizing the size of a character included in the image displayed by the display means before the change of the zoom magnification after display is performed ;
Calculation means for calculating an image resolution for causing the display means to display the character in a predetermined size from the size of the character recognized by the recognition means before the change of the zoom magnification after display is performed ;
The image data of at least one kind of resolution among the image data composed of tiles having a predetermined pixel size having different resolutions according to the image resolution is stored before the zoom magnification after display is designated. Reading means for reading from the means;
Determining means for determining whether image data for obtaining image data having a resolution according to the zoom magnification designated for change is read by the reading means;
The determination means requires image data of two kinds of resolutions as image data for obtaining image data of resolution according to the zoom magnification designated for change, and the read image data is the 2 When it is determined that only one of the two types of resolution image data is read, the remaining resolution image data of the two types of image data is read, and the read image data and the remaining resolution of the read resolution are read. Image data having an intermediate resolution of the image data is generated, and the image data having two different resolutions as the image data for obtaining the image data having the resolution according to the zoom magnification designated by the change is read by the determination unit. If it is determined that the previously read by means, said two different resolutions two different from the image data of the resolution image Day A computer program for a zoom processing means for generating the intermediate resolution picture data of causing a computer to function,
The readout means gives priority to the image areas that can be displayed by the display means in order from the upper left to the lower right of the image area with reference to the center of the image area displayed by the display means. And reading out from the storage means image data composed of tiles having a predetermined pixel size in units of tiles having a predetermined pixel size in accordance with the priority.

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