JP4747780B2 - Image processing apparatus, image processing method, and image processing program - Google Patents

Description

  The present invention relates to an image processing apparatus, an image processing method, and an image processing program. In particular, document data created by an application is separated into layers, raster data is created for each layer, and raster data is created for each layer. The present invention relates to an image processing apparatus, an image processing method, and an image processing program that perform image processing.

  In recent years, documents are created using document creation application software in a computer office such as a word processor, and are distributed by e-mail or stored in a server computer or the like as needed. In general, document creation software generates document data in a unique format. For this reason, the user who receives the document data browses and displays the distributed document data by using software equivalent to the document creation application software used by the document creator.

  On the other hand, environments where documents can be viewed, viewed and edited tend to be diversified. For example, in addition to differences in operating system types and versions, there is an increasing demand for browsing document data in portable information terminals such as PDA (Personal Data Assistance). When considering such various computer environments, there is no longer a situation where the document delivery destination has an environment used when creating document data.

  Therefore, a method has been proposed in which document data is expressed as image data and distributed so that any document can be handled even if there is no specific software at the distribution destination. However, since image data generally has a large data size, it is common to perform image compression processing such as JPEG.

  In the technique disclosed in Patent Document 1, multi-value image data and 1-bit indicating whether each pixel of the multi-value image data is a character from document data created by document creation application software or the like. The image area flag image is generated, and then the position, size, and character color of the character area included in the multi-valued image data is determined based on the image area flag image. The document data is efficiently compressed by performing separate compression in each area.

  In other words, in the above-described prior art, image data in which characters and photographs / graphics are mixed is separated into a character image and other images, and the character image is expressed as a binary image with respect to the character image, such as MMR. Compression is performed using a binary image compression method, and images other than character images are compressed using a multi-value image compression method such as JPEG. When JPEG compression is performed on a character image, mosquito noise is likely to occur when high-frequency components included in the edges of the character portion are compressed. However, by using MMR compression on a character image, generation of mosquito noise is prevented and image quality deterioration occurs. Can be suppressed. As a result, it is possible to express image data with high image quality and high compression of document data.

  However, the above-described technique has a problem that it takes a processing time because a multi-value image must be created by developing document data, and a binary image must be created from the multi-value image.

  Similarly, as a technique for improving the compression ratio of document data, the applicant separates document data created by an application into a plurality of layers (layers), creates raster data for each layer, and converts the raster data to each layer. An image processing method for generating image data having an MRC (Mixed Raster Content) structure by applying compression processing has been proposed (Japanese Patent Application No. 2004-222245). In this image processing method, a high compression rate can be achieved by applying different types of compression processing for each layer.

  12A to 12C are diagrams illustrating an example of image data having an MRC structure. For example, FIG. 12A shows a configuration example of document data. The document data 24 includes a text 26 and graphics 28 drawn in black, a text 30 and graphics 32 drawn in red, and an image 34 created by taking in image data such as a photograph. FIG. 12B shows a state in which portions including images are collected in one layer 36, and this layer 36 can be compressed by a method (for example, JPEG method) for compressing multivalued image data. Further, since this layer 36 is treated as a background, it is called a BG (Background) layer. FIG. 12C shows a state in which portions including text and graphics are collected in one layer 80. Mask data 82 and 84 are configured for each region of the same color. Each can be compressed by a method (for example, MMR method) for compressing binary image data. Since the layer 80 is overwritten on the background, it is called an FG (Foreground) layer, and each mask data can be expressed as a combination of a compression method, a position / size, and color information.

  In the image data included in the MMR compressed area of the FG layer 80, a portion where text or graphics exists corresponds to a “black” pixel. If it is defined that the “white” pixel portion is treated as a transparent area at the time of decoding, the JPEG compressed data of the BG layer 36 is expanded, and then the MMR compressed data of the FG layer 80 is expanded and designated. The original document data 24 can be reproduced by coloring the color information.

JP 2003-244447 A

  As described above, when document data is converted into image data having a multilayer structure, text (character) data is generally assigned to an FG layer and subjected to lossless compression such as MMR compression.

  However, when character data is assigned to the FG layer, the FG layer includes character shape information and character color information, and is subjected to lossless compression, so that the amount of information to be retained is larger than that of the BG layer. As a result, there is a problem that the size of the image data having a multilayer structure is increased.

  By the way, there are various types of documents generally used in business. For example, as shown in FIG. 7, a document for reporting business details in detail is composed of many small characters. On the other hand, as shown in FIG. 8, in the material used for the presentation, it is assumed that the presenter supplements the content of the material. Therefore, the report content is usually simplified and the content is indicated by large characters. Thus, it can be seen that the size of characters used varies depending on the type of document.

  When a report including small characters is converted into image data, the small characters must be imaged at a high resolution in order to ensure the readability of the characters. On the other hand, when converting a document using large characters such as presentation material into image data, a resolution that can recognize the characters is sufficient, and it is not necessary to have a very high resolution. Therefore, in such a document, the size of the image data can be reduced by reducing the resolution.

  However, in a conventional image processing apparatus that converts document data into image data having a multi-layer structure, in order to obtain image data in which character readability is ensured, conversion to image data while the user changes various resolution settings. Need to be repeated on a trial and error basis, and there is a marked lack of convenience.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image processing apparatus and image processing capable of obtaining image data having a smaller multilayer structure while ensuring the readability of characters. A method and an image processing program are provided.

In order to achieve the above object, an image processing apparatus of the present invention analyzes data input means for inputting document data, document data input by the data input means, and determines the type of drawing command included in the document data. Based on the relationship between the data analysis means for identifying, and when the drawing command is a character drawing command, the typeface and the character size are detected as character information from the character drawing command, and the character size and resolution set in advance for each typeface Resolution determining means for determining the resolution corresponding to the smallest character size among the detected character sizes for each typeface, and determining the highest resolution among the determined resolutions as the resolution at the time of character drawing; and the data According to the type of drawing command identified by the analysis means, the drawing command included in the document data is an image having a multilayer structure in which the image data is divided into a plurality of layers having different attributes. Generating image data of the layer to which the character rendering command is assigned using the resolution determined by the resolution determining means and a layer assigning means to be assigned to any layer of the data, and using a preset resolution And image data generating means for generating image data of other layers.

In the image processing apparatus of the present invention, when document data is input from the data input means, the data analysis means analyzes the input document data and identifies the type of drawing command included in the document data. The layer allocating unit converts the drawing command included in the document data according to the type of the drawing command identified by the data analyzing unit to any one of the multilayered image data in which the image data is divided into a plurality of layers having different attributes. Assign to a tier. At this time, when the drawing command is a character drawing command, the resolution determining means detects the font and the character size as character information from the character drawing command, and based on the relationship between the character size and the resolution set in advance for each font. Thus, the resolution corresponding to the smallest character size among the detected character sizes is obtained for each typeface, and the highest resolution among the obtained resolutions is determined as the character drawing resolution.

  Then, the image data generation means generates image data of the layer to which the character drawing command is assigned using the resolution determined by the resolution determination means, and outputs image data of other layers using the preset resolution. Since it is generated, characters are drawn with the lowest resolution that guarantees the readability of all characters. As a result, it is possible to obtain image data having a multilayer structure having a smaller size while ensuring the readability of characters.

  As described above, according to the present invention, there is an effect that it is possible to obtain image data having a multilayer structure with a smaller size while ensuring the readability of characters.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. Hereinafter, image data having an MRC structure is referred to as “layer-specific image data”.

(First embodiment)
<Schematic configuration of image processing apparatus>
FIG. 1 is a diagram showing a schematic configuration of an image processing apparatus. The image processing apparatus 10 includes an analysis processing unit 16 that analyzes the document data 12 or the print data 14, and a layer image processing unit 22 that generates layer-specific image data 20 from the image information 18 obtained by the analysis. Yes. With this configuration, when the document data 12 or the print data 14 is input, the image processing apparatus 10 generates and outputs layer-specific image data 20 that is an image data file in a multilayer format.

  Here, the document data 12 is data defined uniquely for an application program such as a word processor. The print data 14 is data that is generated while document data is being output by the image forming apparatus. For example, PDL (page description language) data corresponds to this in a printing apparatus such as a printer. The document data 12 or the print data 14 is composed of drawing objects (character objects, graphics objects, image objects).

  A drawing object is generally expressed by a drawing command. For example, a character drawing command is used to represent a character object, a drawing command of a geometric figure such as a rectangle is used to represent a graphics object, and an image drawing command is used to represent an image object.

  The image information 18 includes an edge array, tag data, and circumscribed rectangle data. The edge array represents raster data. The tag data indicates attributes of document components such as “text” and “photo”. The circumscribed rectangle data is data generated for each tag type, and indicates the circumscribed rectangle of the area where the drawing object indicated by the tag exists. It is guaranteed that the drawing object does not exist outside the circumscribed rectangle.

<Image data having MRC structure>
FIGS. 2A to 2D are diagrams showing examples of image data for each layer having a three-layer MRC structure. FIG. 2A shows a configuration example of document data. The document data 24 includes a text 26 and graphics 28 drawn in black, a text 30 and graphics 32 drawn in red, and an image 34 created by taking in image data such as a photograph. Note that the document example shown in FIG. 2A is the same as the document example shown in FIG.

  FIG. 2B shows a state in which portions including images are collected in one layer 36. The layer 36 can be compressed by a method (for example, JPEG method) for compressing multivalued image data. Further, since this layer 36 is treated as a background (background image), it is called a BG (Background) layer or a background layer. The layer configuration illustrated in FIG. 2B is also the same as the layer configuration illustrated in FIG.

  The three-layer MRC structure shown in FIG. 2 is different from the N-layer MRC structure (see FIG. 12) in the foreground expression format. That is, in the case of the N-layer MRC structure, mask data is configured for each region of the same color, and each mask data is expressed as a combination of a compression method, position / size, and color information. In the case of the MRC structure, the shape of the foreground drawing object 38 included in the entire page is represented by one mask data 40 (see FIG. 2D), and the color information of the foreground drawing object 38 is represented by one image data 42. (See FIG. 2C). In this example, the image data 42 includes a color information (black) area 44 and a color information (red) area 46.

  Mask data 40 and image data 42 are compressed separately. In general, reversible compression such as MMR method is applied to mask data, and image data expressing color information is compressed such as JPEG method and JBIG2 method. Thus, the compression rate can be increased by compressing in a different manner. Each of these data is a foreground to be overwritten on the background, but a layer composed of the mask data 40 is called a mask layer, and a layer composed of the image data 42 is an FG (Foreground) layer or the foreground. Referred to as a layer. When there is no need to distinguish between the mask layer and the foreground layer, the mask layer and the foreground layer are referred to as a foreground layer or an FG layer.

<Image processing procedure>
FIG. 3 is a functional block diagram of the image processing apparatus 10. Hereinafter, the configuration of the image processing apparatus 10 will be described in detail with reference to FIG. In the present embodiment, the above-described three-layered MRC-structured image data 20 is output. Characters are assigned to the foreground layer, and graphics and images are assigned to the background layer.

  As described above, the image processing apparatus 10 includes the analysis processing unit 16 that analyzes the document data 12 or the print data 14 (input data), and the layer image processing unit 22 that generates the layer-specific image data 20. . The analysis processing unit 16 analyzes the input data to identify a drawing command, and if the identified drawing command is a character drawing command, the character resolution determining unit 52 determines the resolution at the time of character drawing. , Is composed of.

  Further, the layer image processing unit 22 selects either the FG image storage unit 62 or the BG image storage unit 64 for assigning the drawing object to the FG layer or the BG layer, and the layer assignment result and the drawing object. The character processing unit 56, the graphics processing unit 58, the image processing unit 60, the MMR compression unit 66 that compresses the mask data stored in the FG image storage unit 62 by the MMR method, and the FG image storage unit 62 The JPEG compression unit 68 compresses the foreground color data and the background image stored in the BG image storage unit 64 by the JPEG method, and the format unit 70 embeds the MMR compressed data and the JPEG compressed data in a predetermined file format. Has been.

  Next, an image processing procedure performed by the image processing apparatus 10 will be described. In the present embodiment, image processing is performed in two passes: a “first pass” for determining the resolution at the time of character drawing and a “second pass” for generating image data by layer. The second pass is executed after the first pass is finished.

(1) First Pass In the first pass, when the document data 12 or the print data 14 is input, the input data analysis unit 50 analyzes the input data 12 (or 14), and the type of drawing command is determined. Identified. When the identified drawing command is a character drawing command, the “character drawing command” is transmitted to the character resolution determination unit 52. The character resolution determination unit 52 analyzes the contents of the character drawing command delivered each time, detects information about characters to be drawn, and saves the information in an internal buffer (not shown) as storage means.

  In the first pass, the input data analysis unit 50 transmits a drawing command only to the character resolution determination unit 52 and does not transmit a drawing command to the layer allocation unit 54. When the input data analysis unit 50 finishes analyzing all drawing commands, the input data analysis unit 50 transmits an “analysis end notification” to the character resolution determination unit 52. Upon receiving the analysis end notification, the character resolution determining unit 52 determines the character output resolution based on the character information stored in the internal buffer, and notifies the character processing unit 56 of the determined output resolution.

(2) Second Pass In the second pass, first, the input data analysis unit 50 analyzes the input data 12 (or 14) to identify the type of drawing command. The identified drawing command is transmitted to the layer assignment unit 54 and assigned to either the FG layer or the BG layer. The layer allocation unit 54 transmits a drawing command to any of the character processing unit 56, the graphics processing unit 58, and the image processing unit 60 according to the type of the drawing command. At this time, the layer assignment result is notified to each unit together with the drawing command.

  Each of the character processing unit 56, the graphics processing unit 58, and the image processing unit 60 selects one of the FG image storage unit 62 and the BG image storage unit 64 based on the layer assignment result, and selects one of the drawing objects. Draw in the storage unit. At this time, the character processing unit 56 generates mask data representing the shape of the character using the output resolution notified from the character resolution determination unit 52 in the first pass. On the other hand, the graphics processing unit 58 and the image processing unit 60 generate an image with a preset output resolution.

  The mask data stored in the FG image storage unit 62 is subjected to MMR compression by the MMR compression unit 66 and input to the format unit 70. The foreground color data stored in the FG image storage unit 62 is subjected to JPEG compression by the JPEG compression unit 68 and input to the format unit 70. The background image stored in the BG image storage unit 64 is subjected to JPEG compression by the JPEG compression unit 68 and input to the format unit 70. The format unit 70 embeds the MMR compressed data and the JPEG compressed data in a predetermined file format, and outputs the obtained layer-specific image data 20.

<Resolution determination process>
Next, the “resolution determination process” executed by the character resolution determination unit 52 will be described in detail.
FIG. 4 is a chart showing the structure of the character drawing command. As shown in FIG. 4, the “character drawing command” used in the present embodiment includes a drawing command name field and a parameter field. The drawing command name is a name for identifying various commands, and is “character drawing” in the case of a character drawing command. The parameter indicates the attribute of the character to be drawn. The “drawing position” indicating the position on the page where the character is to be drawn, the “typeface name” indicating the typeface of the character to be drawn, and the point indicating the size of the character It consists of a “size” such as a number and a “color value” that specifies a color value (RGB value) of a character.

FIG. 5 is a flowchart showing a processing routine executed by the character resolution determination unit 52.
When document data 12 or print data 14 is input to the image processing apparatus 10, the processing is started. First, in step 100, an internal buffer (not shown) that holds current minimum character size information is initialized, and the current minimum Set to "no information" state where character size information is not retained. Here, “current minimum character size information” is the size information of the smallest character among the character rendering commands included in the input data, and is held in the internal buffer of the character resolution determination unit 52 and functions as an internal variable.

  Next, in step 102, it is determined whether or not there is an instruction from the input data analysis unit 50. In the case of negative determination, the determination is repeated at predetermined intervals until an instruction is given. If the determination is affirmative, the following processing is performed according to the instruction content. When a character drawing command is received from the input data analysis unit 50, the process proceeds to step 104, where the received character drawing command is analyzed to detect “character size information”. In the character drawing command used in this embodiment, the character size is specified by the number of points as shown in FIG.

  When the character size information is detected, it is determined in the next step 106 whether or not the internal buffer is in an initialized state. In the case of an affirmative determination, since the received drawing command is the first character drawing command, the process proceeds to step 110, and the detected character size information is held in the internal buffer. As a result, the current minimum character size information in the internal buffer is updated with the detected character size information.

  In the case of negative determination in step 106, since it is a character drawing command for the second and subsequent times, the process proceeds to step 108, where the detected character size information is compared with the current minimum character size information held in the internal buffer to detect it. It is determined whether the selected character size is smaller than the current minimum character size. If the determination is affirmative, since the detected character size is the minimum character size, the process proceeds to step 110, and the current minimum character size information in the internal buffer is updated with the detected character size information.

  After the update is completed in step 110, the process returns to step 102 and waits for the next instruction to be input from the input data analysis unit 50. Also in the case of a negative determination in step 108, the process returns to step 102 and waits for the next instruction from the input data analysis unit 50.

  When the analysis end notification is received in step 102, the process proceeds to step 112, where the current minimum character size information held in the internal buffer is read, and in the next step 114, the output resolution corresponding to the current minimum character size information is determined. . The method for determining the output resolution will be described later. When the output resolution is determined in step 114, the process proceeds to the next step 116, the determined output resolution is notified to the character processing unit 56, and the routine is terminated.

  Next, the output resolution determination method executed in step 114 will be described. FIG. 6 is a correspondence table showing the correspondence between the minimum character size and the output resolution. In the present embodiment, the resolution at which the readability of the minimum size of the characters used is guaranteed is given in the correspondence table shown in FIG. This correspondence table is held in an internal buffer (not shown) of the character resolution determination unit 52. In step 114, by referring to this correspondence table, the lowest resolution can be obtained while ensuring readability. For example, if the current minimum character size is 8 points or 9 points, it can be seen that the lowest readable resolution is 200 DPI.

<Application examples to various documents>
FIG. 7 is a diagram showing a document example of a report, and FIG. 8 is a diagram showing a document example for the purpose of presentation. In the case of the document shown in FIG. 7, the value of the current minimum character size information is “8p (8 points)”. When the output resolution corresponding to “8p” is searched with reference to the correspondence table of FIG. 6, 200 DPI is obtained. Therefore, characters are drawn at an output resolution of 200 DPI, and readability is ensured even for characters of the minimum size of 8 points. On the other hand, in the case of the document shown in FIG. 8, the value of the current minimum character size information is “16p (16 points)”, and when the output resolution corresponding to “16p” is searched with reference to the correspondence table of FIG. 75 DPI. Therefore, characters are drawn at an output resolution of 75 DPI, and the data size of the foreground image data to which the characters are assigned is reduced.

  As described above, in the present embodiment, the character size information is detected from the character drawing command, the size information of the minimum character included in the input data is acquired, and the readability of the character of the minimum size is guaranteed. Since the output resolution is determined, it is possible to obtain layered image data having a smaller size while ensuring the readability of characters.

(Second Embodiment)
In the second embodiment, the user can select whether or not to use the output resolution automatic adjustment function. FIG. 9 is a functional block diagram of an image processing apparatus according to the second embodiment. The configuration is the same as that of the image processing apparatus according to the first embodiment (see FIG. 3) except that the resolution determination method instruction unit 72 is added. Omitted.

  The resolution determination method instruction unit 72 is an instruction input unit for the user to instruct whether or not the character resolution determination unit 52 determines the output resolution. Specifically, it is realized as a user interface such as an operation panel.

  FIG. 10 is a diagram illustrating an example of a user interface. FIG. 10 shows a resolution designation dialog 74 as an example of a user interface for the user to instruct whether or not to determine the output resolution. In this dialog 74, it is possible to select either “determine from the minimum character size” or “designate a fixed resolution” as the resolution determination method. Also, an input box 76 for inputting a fixed resolution is provided. When “Specify fixed resolution” is selected, the user can input a fixed resolution value.

  Next, an image processing procedure will be described. In the present embodiment, when an instruction is input from the resolution determination method instruction unit 72, the user instruction result is notified to the input data analysis unit 50. For example, when the user selects “determine from the minimum character size” in the dialog 74, the first pass is executed as in the first embodiment, and the second pass after the first pass is completed. Execute. On the other hand, when the user selects “specify fixed resolution” in the dialog 74, the input data analysis unit 50 notifies the character processing unit 56 of the resolution specified by the user, and the first pass is not executed. Perform only the second pass.

  As described above, in this embodiment, the user can select whether or not to use the output resolution automatic adjustment function. When the automatic adjustment function of the output resolution is selected, the character size information is detected from the character drawing command and the size information of the minimum character included in the input data is obtained as in the first embodiment. Since the output resolution is determined so as to ensure the readability of the character of the minimum size, it is possible to obtain layered image data of a smaller size while ensuring the readability of the character.

(Third embodiment)
In the first and second embodiments, the character size information is detected and the output resolution is determined. In the third embodiment, in addition to the character size information, the font information also determines the output resolution. To use. That is, the method for determining the output resolution is different from that of the other embodiments. Since other points such as the configuration of the image processing apparatus are the same as those in the first embodiment, description thereof will be omitted.

  The procedure of resolution determination processing when character size information and typeface information are used will be described with reference to the flowchart shown in FIG. First, in step 100, an internal buffer (not shown) that holds the current minimum character size information is initialized to a “no information” state in which the current minimum character size information is not held. In the present embodiment, “current minimum character size information” is held for each typeface.

  Next, in step 102, it is determined whether or not there is an instruction from the input data analysis unit 50. In the case of negative determination, the determination is repeated at predetermined intervals until an instruction is given. If the determination is affirmative, the following processing is performed according to the instruction content. If a character drawing command is received from the input data analysis unit 50, the process proceeds to step 104, where the received character drawing command is analyzed to detect “character size information” and “typeface information”.

  When character size information and typeface information are detected, it is determined in the next step 106 whether or not the internal buffer is in an initialized state. If the determination is affirmative, the process proceeds to step 110, and the detected character size information is held in the internal buffer. In the case of negative determination, the process proceeds to step 108, and for each typeface, the detected character size information is compared with the current minimum character size information held in the internal buffer, and the current minimum character of the typeface whose detected character size is the same. Determine whether it is smaller than the size. In the case of an affirmative determination, since the detected character size is the minimum character size, the process proceeds to step 110, and the current minimum character size information in the internal buffer is obtained for the typeface determined to be smaller than the current minimum character size. Update with detected character size information.

  In the first embodiment, the character resolution determination unit 52 obtains the minimum size of the character used. In the third embodiment, the character resolution determination unit 52 obtains the minimum size of the character for each typeface. For example, in the case of a document including two types of characters with different typefaces, such as “Gothic” and “Mincho”, the current minimum character size information for “Gothic” and the current minimum character size information for “Mincho” Is held in an internal buffer.

  After the update is completed in step 110, the process returns to step 102 and waits for the next instruction to be input from the input data analysis unit 50. Also in the case of a negative determination in step 108, the process returns to step 102 and waits for the next instruction from the input data analysis unit 50.

  When the analysis end notification is received in step 102, the process proceeds to step 112, where the current minimum character size information held in the internal buffer is read for each typeface, and in the next step 114, the output resolution corresponding to the current minimum character size information is read. To decide. The method for determining the output resolution will be described later. When the output resolution is determined in step 114, the process proceeds to the next step 116, the determined output resolution is notified to the character processing unit 56, and the routine is terminated.

  Next, the output resolution determination method executed in step 114 will be described. FIG. 11 is a correspondence table showing the correspondence between the minimum character size and the output resolution for each typeface. In the present embodiment, the resolution at which the readability of the minimum size of the characters used is guaranteed is given for each typeface in the correspondence table shown in FIG. In step 114, by referring to this correspondence table, the lowest resolution is searched while guaranteeing the readability for each typeface, and the highest resolution among the searched resolutions is set as the output resolution.

  For example, if the current minimum character size for Gothic is 10 points, the lowest readable resolution is 150 DPI, and if the current minimum character size for Mincho is 10 points, the lowest readable resolution is 200 DPI. . Therefore, the resolution that guarantees the readability of all characters used is 200 DPI. The resolution for which readability is guaranteed varies depending on the typeface, and generally, a higher resolution is required in the Mincho to ensure readability than Gothic. Thus, the resolution which guarantees readability for every typeface is calculated | required, and the highest resolution is selected from the resolution, and the readability of the character of the minimum size is guaranteed about all the typefaces.

  As described above, in the present embodiment, the character size information and the typeface information are detected from the character drawing command, the size information of the minimum character included in the input data is acquired for each typeface, and the minimum size for all the typefaces. Since the output resolution is determined so as to ensure the readability of the characters, it is possible to obtain image data by layer having a smaller size while ensuring the readability of the characters.

  In the above, the minimum character size for each typeface is determined first, then the resolution corresponding to the minimum size for each typeface is determined, and the highest resolution is selected among them. A resolution that guarantees readability is obtained with reference to the correspondence table, and the highest resolution among the resolutions may be selected.

(Fourth embodiment)
In the first to third embodiments, the example in which the image data for each layer having the three-layer MRC structure is output has been described. In the fourth embodiment, the image for each layer having the N-layer MRC structure shown in FIG. An example of outputting data will be described. Since the configuration of the image processing apparatus is the same as that of the first embodiment except that the input from the FG image storage unit 62 to the JPEG compression unit 68 is not performed, the description thereof is omitted.

  The image processing procedure will be described below. When the document data 12 or the print data 14 is input, the input data analysis unit 50 analyzes the input data 12 (or 14) and identifies the type of drawing command. When the identified drawing command is a character drawing command, the “character drawing command” is transmitted to the character resolution determination unit 52 and also to the layer allocation unit 54.

  The character resolution determination unit 52 analyzes the contents of the character drawing command passed each time, detects the information of the character to be drawn, determines the lowest resolution with readability based on the character size information, and determines the determined output. The resolution is transmitted to the character processing unit 56 each time.

  The layer allocation unit 54 transmits a drawing command to any of the character processing unit 56, the graphics processing unit 58, and the image processing unit 60 according to the type of the drawing command. At this time, the layer assignment result is notified to each unit together with the drawing command. The character processing unit 56 associates the character drawing command received from the layer allocation unit 54 with the output resolution of the character drawing command received from the character resolution determination unit 52, and stores it in an internal buffer (not shown).

  Each time the graphics processing unit 58 and the image processing unit 60 receive a drawing command, the graphics processing unit 58 and the image processing unit 60 select either the FG image storage unit 62 or the BG image storage unit 64 based on the layer assignment result, Draw in the storage. On the other hand, the character processing unit 56 only stores the drawing command and the output resolution in association with each other in the internal buffer when the drawing command is received.

  When the input data analysis unit 50 finishes analyzing all drawing commands, the input data analysis unit 50 transmits an “analysis end notification” to the character processing unit 56 via the layer assignment unit 54. When the character processing unit 56 receives the analysis end notification, the character processing unit 56 generates mask data representing the shape of the character using the drawing command and the output resolution stored in the internal buffer. The character processing unit 56 may output mask data and color values for each character (for each drawing command) to the FG image storage unit 62, or for each character having the same output resolution and the same color value. The mask data and the color value may be combined into one mask data and output to the FG image storage unit 62. It is also possible to combine characters having the same character size and the same color value into one mask data. On the other hand, the graphics processing unit 58 and the image processing unit 60 generate an image with a preset output resolution.

  The mask data stored in the FG image storage unit 62 is subjected to MMR compression by the MMR compression unit 66 and input to the format unit 70 together with the color information. The image stored in the BG image storage unit 64 is subjected to JPEG compression by the JPEG compression unit and input to the format unit 70. The format unit 70 embeds the MMR compressed data and the JPEG compressed data in a predetermined file format, and outputs the obtained layer-specific image data 20.

  As described above, in the present embodiment, even if the layer-by-layer image data has an N-layer MRC structure, the character size information is detected from the character drawing command and the size information of the minimum character included in the input data is acquired. In addition, since the output resolution is determined so as to ensure the readability of the minimum size character, it is possible to obtain smaller-sized layered image data while ensuring the character readability.

  In particular, in the fourth embodiment, the size information of the minimum character included in each character drawing command is acquired, and the output resolution is determined so as to ensure the readability of the character of the minimum size for each character drawing command. The readability of characters can be ensured reliably.

  In the above description, the output resolution is determined for each character drawing command and the mask data is generated for each character drawing command. However, the N-layer MRC structure has a feature that the degree of freedom of foreground expression is large. Therefore, in addition to generating mask data for each character drawing command, the character processing unit can generate mask data for each character having the same output resolution (or the same character size) and color value. .

It is a figure which shows schematic structure of an image processing apparatus. It is a figure which shows an example of the image data which has a 3 layer MRC structure. 1 is a functional block diagram of an image processing apparatus according to a first embodiment. It is a chart showing the structure of a character drawing command. It is a flowchart which shows the process sequence of a character resolution determination part. 6 is a correspondence table showing a correspondence relationship between a minimum character size and an output resolution. It is a figure which shows the example of a document of a report. It is a figure which shows the example of a document aiming at the presentation. It is a functional block diagram of the image processing apparatus which concerns on 2nd Embodiment. It is a figure which shows the display of a user interface. It is a correspondence table showing the correspondence between the minimum character size and the output resolution for each typeface. It is a figure which shows an example of the image data which has N layer MRC structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image processing apparatus 12 Document data 14 Print data 16 Analysis process part 18 Image information 20 Image data classified by layer 22 Layer image process part 24 Document data 26 Text 28 Graphics 30 Text 32 Graphics 32 Layer 34 Image 36 Layer 38 Drawing object 40 Mask data 42 Image data 44 Region 46 Region 50 Input data analysis unit 52 Character resolution determination unit 54 Layer allocation unit 56 Character processing unit 58 Graphics processing unit 60 Image processing unit 62 FG image storage unit 64 BG image storage unit 66 MMR compression unit 68 JPEG compression section 70 Format section 72 Resolution determination method instruction section 74 Dialog 76 Input box 80 Layer 82 Mask data

Claims (11)

Data input means for inputting document data;
Data analysis means for analyzing the document data input by the data input means and identifying the type of drawing command included in the document data;
When the drawing command is a character drawing command, the typeface and the character size are detected as character information from the character drawing command, and the detected character size is determined based on the relationship between the character size and the resolution set in advance for each typeface. Resolution determination means for determining the resolution corresponding to the smallest character size for each typeface, and determining the highest resolution among the obtained resolutions as the resolution at the time of character drawing ,
Depending on the type of drawing command identified by the data analysis means, the drawing command included in the document data is assigned to one of the layers of image data having a multilayer structure in which the image data is divided into a plurality of layers having different attributes. Tier assignment means;
Image data generating means for generating image data of a layer to which the character drawing command is assigned using the resolution determined by the resolution determining means and generating image data of another layer using a preset resolution When,
An image processing apparatus comprising:   The image processing apparatus according to claim 1, wherein the document data is document data created on a computer or print data generated when printing the document data.   The image processing apparatus according to claim 1, wherein the character information is selected from a group consisting of a drawing position, a typeface, a character size, and a color value. The image data of the layer in which the character rendering command is assigned with compressed by MMR method, data compression means for compressing the image data of the other layers in the JPEG method, to claim 1, characterized in that further comprising 4. The image processing apparatus according to any one of items 3 . When an instruction input unit for inputting an instruction regarding a resolution determination method at the time of character drawing and an instruction to automatically determine the resolution from the instruction input unit, the highest resolution is set as the resolution at the time of character drawing. The image processing apparatus according to claim 1 , further comprising: a control unit that controls the resolution determination unit so as to determine the resolution. The multi-layered image data comprises a foreground layer including a mask layer representing the shape of a drawing object in the image data and a color layer for storing foreground color information, and a background layer for storing background image data, The image processing apparatus according to claim 1, wherein a character drawing command is assigned to the foreground layer. The multi-layered image data includes a foreground layer including a plurality of mask data representing a shape for a foreground drawing object and foreground color information, and a background layer for storing background image data, and the character drawing command The image processing apparatus according to claim 1 , wherein the image processing apparatus is assigned to a foreground layer. The image processing apparatus according to claim 7 , wherein the resolution determining unit determines a resolution at the time of character drawing for each of a plurality of mask data included in the foreground layer based on detected character information. . The image processing apparatus according to claim 8 , wherein the plurality of mask data are generated for each character drawing command or for each resolution at the time of character drawing. A data entry step for entering document data;
A data analysis step of analyzing document data input by the data input means and identifying a type of a drawing command included in the document data;
When the drawing command is a character drawing command, the typeface and the character size are detected as character information from the character drawing command, and the detected character size is determined based on the relationship between the character size and the resolution set in advance for each typeface. A resolution determination step for determining a resolution corresponding to the smallest character size for each typeface, and determining the highest resolution among the obtained resolutions as the resolution at the time of character drawing ,
Depending on the type of drawing command identified by the data analysis means, the drawing command included in the document data is assigned to one of the layers of image data having a multilayer structure in which the image data is divided into a plurality of layers having different attributes. Tier assignment step;
An image data generation step of generating image data of a layer to which the character drawing command is assigned using the resolution determined by the resolution determining means and generating image data of another layer using a preset resolution When,
An image processing method comprising: By computer
A data entry step for entering document data;
A data analysis step of analyzing document data input by the data input means and identifying a type of a drawing command included in the document data;
When the drawing command is a character drawing command, the typeface and the character size are detected as character information from the character drawing command, and the detected character size is determined based on the relationship between the character size and the resolution set in advance for each typeface. A resolution determination step for determining a resolution corresponding to the smallest character size for each typeface, and determining the highest resolution among the obtained resolutions as the resolution at the time of character drawing ,
Depending on the type of drawing command identified by the data analysis means, the drawing command included in the document data is assigned to one of the layers of image data having a multilayer structure in which the image data is divided into a plurality of layers having different attributes. Tier assignment step;
An image data generation step of generating image data of a layer to which the character drawing command is assigned using the resolution determined by the resolution determining means and generating image data of another layer using a preset resolution When,
An image processing program for executing

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