JP2001171185A - Image-forming apparatus and method for processing image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a printing overrun by estimating a processing time required for a rendering process in accordance with a length of a period in which an access conflict for a rendering part and an output part to concurrently access to the same physical memory is likely to occur. SOLUTION: The rendering part 334 estimates the time required for rendering for each band from intermediate data stored in an intermediate data memory part 333, and simulates the rendering process for each band or the like on the basis of the estimated time. Whether accessing to the same physical memory conflicts or not is checked from the simulation result. Which of the band- processings conflicts is detected when the conflict takes place. A corresponding safety coefficient is obtained from a safety coefficient memory part 335 on the basis of the detected result, based on which the time required for rendering for each band is estimated again. The estimated value is compared with a preset predetermined value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus for developing print data expressed in PDL or the like in a memory in the form of a bit map or the like and performing print output, and an image processing method for the image forming apparatus. .

[0002]

2. Description of the Related Art In an image forming apparatus which receives print data from an external device (host) such as a personal computer and prints the print data, the received print data in a predetermined format is temporarily stored in a memory, read out from the memory, and read in a bitmap format. Generally, data is converted to data, temporarily stored in a memory, and finally read out and printed. In such an image forming apparatus, since the resolution of image information has been increased and the number of values has been increased, the memory capacity required when converting the original print data into bitmap data and expanding the data on the memory is reduced. It tends to increase.

FIG. 1 shows the overall flow of data of such an image forming apparatus 1, FIG. 2 is a schematic block diagram of the image forming apparatus 1, and FIG. 3 shows the flow of data in band processing. FIG. First, the overall flow of data will be described with reference to FIG. In the image forming apparatus 1, first, the receiving unit 3 receives the print data sent from the external device (host) 2. Data is exchanged via the system bus 10 inside the image forming apparatus 1. The data received by the receiving unit 3 is converted into intermediate data in a format that can be easily developed into a bitmap, and stored in a memory (not shown).
Then, the rendering unit 4 performs rendering processing on the intermediate data to generate bitmap data, and temporarily stores the bitmap data in the memory 5 (in FIGS. 2 and 3, the physical memories 11 and 12). The output unit 6 reads out the bitmap data from the memory 5 in synchronization with the operation of the printing unit 7 and sends out the bitmap data to the printing unit 7, and the printing unit 7 prints the bitmap data, thus completing the printing.

By the way, for example, in an image forming apparatus such as a laser printer, not all information of one page of bitmap data is developed on the memory 7 but, as shown in FIG. There is a method that employs a method in which the sheet is divided into a number of strip-shaped bands (band 1 to band 9) by dividing the sheet in a direction perpendicular to the transport direction. In this case, the image forming apparatus 1 converts the print data received from the external apparatus 2 into intermediate data and holds it for one page, and the rendering unit 4 converts the intermediate data into bitmap data for each of the divided bands. Generate

The image forming apparatus 1 has a physical memory 1 (1
1), a physical memory 2 (12) is provided, and an area of the band memory 1 is provided in the physical memory 1 (11), and an area of the band memory 2 is provided in the physical memory 2 (12). Is secured. Here, "physical memory" refers to a memory in which a data bus, an address bus, and the like are independent and can be accessed separately. Here, the physical memory 1 (11) and the physical memory 2 (12)
Each is a separate device, and each is provided with a bus. Therefore, it is possible to access the physical memory 1 (11) and the physical memory 2 (12) at the same time, but it is not possible to simultaneously access the area of the band memory 1 and other areas within the same physical memory 1 (11). .

[0006] Each band memory has a capacity enough to store bitmap data for one band of the bands 1 to 9. When actually printing, first, rendering is performed for band 1 and the obtained bitmap data is stored in band memory 1 of physical memory 1 (11). When the rendering for band 1 is completed, the rendering for band 2 is started,
The obtained bitmap data is stored in the band memory 2 of the physical memory 2 (12). At this time, the output unit reads the bitmap data of the band 1 from the band memory 1 and outputs the read bitmap data to the printing unit 7. And the printing unit 7 performs the printing operation. When rendering for band 2 and reading from band memory 1 are completed, rendering for band 3 is started, and the obtained bitmap data is stored in physical memory 1.
The output unit reads out the bitmap data of band 2 from the band memory 2 and sends the data to the printing unit 7 while storing the data in the band memory 1 of (11), and the printing unit 7 also performs the printing operation. Thereafter, the same operation is repeated while using the band memories 1 and 2 alternately, and 9
When rendering processing and printing for the band are completed, 1
Image formation for a page is completed.

However, when printing is performed by such a method, especially in an image forming apparatus such as a laser printer in which the transport time of the paper is determined by the rotation speed of the electrostatic drum, the transport time of one band of paper is It is necessary to render one band of intermediate data. A situation where this condition is not satisfied is called “print overrun”, and if the printing operation is performed as it is, the printing result will be incomplete.

Conventionally, in order to avoid incomplete printing when a print overrun occurs, at the stage of generating intermediate data based on data received from a host, the time required for rendering for each band is estimated and In addition to the above two band memories, a method of securing a third band memory for one more band has been proposed. In this method, for a band whose rendering time is expected to exceed the paper transport time for one band, rendering is performed in advance before paper transport (printing operation) is started to generate bitmap data. In advance (pre-rendering), this is stored in the third band memory. Then, when the paper transport is started, the rendering and print output are performed by alternately using the two band memories as described above, except for the bands that require a rendering time that exceeds the time required for the paper transport for one band. When it is time to print a band whose rendering time exceeds the time required to convey the paper for one band, the bit map data is read from the third band memory and the printing process is performed. By performing such processing, an incomplete print result in a situation where a print overrun occurs has been avoided.

The estimated time obtained by estimating the time required for the above-described rendering is simply the time required for the rendering. Actually, the estimated time is estimated by an interrupt process or the like in controlling the printing unit. There may be a time difference. Therefore, a safety factor is further prepared for the time predicted as described above, for example,
When the predicted rendering time reaches 80% of the paper transport time for one band, it is determined that a print overrun has occurred and rendering in real time cannot be performed, and pre-rendering has been performed in advance. There has been an image forming apparatus in which bitmap data is stored in the above-described third band memory. By providing such a safety coefficient, an incomplete print result is prevented from occurring even when the actual rendering processing is delayed more than the predicted time.

However, the degree to which the actual rendering process is delayed from the predicted time should originally be different for each piece of data to be printed. However, in the conventional apparatus, the above-described safety coefficient is set uniformly. I was For this reason, depending on the data to be printed, duplication of accesses to the same physical memory occurs frequently, and the delay time of the rendering process exceeds the predicted time multiplied by the safety factor, and a print overrun occurs. There was sometimes.

FIG. 4 is a flow chart showing the processing performed by the conventional image forming apparatus shown in FIGS. 1 to 3, and shows the processing contents of the rendering unit 4 and the output unit 6 and the physical memory 1 (11). Band memory 1 and physical memory 2 (1
As for the data held by the band memory 2 in 2), the temporal change thereof is shown by taking time along the vertical axis downward. For example, regarding band 1, the rendering unit 4 performs rendering during a period from time t0 to time t1, and stores the result in the band memory 1 as an output image (bitmap data). The data stored in the band memory 1 is read and printed by the output unit 6 during a period from time t1 to time t2.

By the way, the time required for rendering each band differs for each band. In FIG.
The times t1-t0, t1-t2,... Are set to a time sufficient for performing the printing process for one band (conveying process of the paper for one band). Regarding the band 3, the rendering of the band 2 does not start immediately after the end, but cannot be started until the time t3. This is because the band memory cannot write the bitmap data of the next band unless all the data in the band memory is read out. Because it is hanging. Therefore, as can be seen from FIG. 4, for a band for which rendering is completed in a relatively short time, the waiting time of the rendering process is required after rendering of the band is completed until rendering of the next band is started. Has occurred.
This time causes a delay in the entire processing.

Therefore, a method of further increasing the band memory in each physical memory is considered. For example, as shown in FIG. 5 (corresponding to FIG. 3), the areas of the band memory 1 and the band memory 3 are secured in the physical memory 1 (111), and the band memory 2 is stored in the physical memory 2 (112). And a case where the band processing is executed while securing the area of the band memory 4. FIG. 6 is a flowchart showing how the band processing is performed in the configuration shown in FIG.

Here, attention is paid to band 2 and band 3. For band 2, the rendering process is started at time t1, and the rendering process is continued shortly before time t2. The rendering process of band 3 is performed when the rendering process of band 2 is completed (a little before time t2).
, And this rendering process continues until a little after time t3. Here, the bitmap data obtained as a result of the band 2 rendering process is stored in the physical memory 2
Bitmap data stored in the band memory 2 of (112) and obtained as a result of the band 3 rendering process is as follows:
It is stored in the band memory 4 of the physical memory 2 (112). That is, the band memories storing the bitmap data of these two bands are different, but the physical memories are the same.

Therefore, when the output unit 106 starts reading the bitmap data of band 2 from time t2, time t3 at which the rendering processing of band 3 ends.
The data writing and reading are performed concurrently with respect to the same physical memory 2 (112) until a little after (indicated by oblique lines). That is, during the period of the band 3 indicated by the diagonal line, the output unit and the rendering unit may access the same physical memory at the same time. The same occurs for the other shaded portions in FIG.

In such a period, the rendering unit 104 and the output unit 106 are used to avoid contention for bus access.
Needs to interrupt or delay the processing. Furthermore, in order to prevent the printing unit from interrupting the printing process, the process of the output unit 106 must be executed with priority. In short, during this period, rendering of the rendering unit is delayed due to access to the physical memory by the output unit 106. Therefore, the larger the shaded area shown in FIG. 6, the lower the efficiency of the rendering process and the greater the risk of print overrun.

[0017]

Assuming that the estimated rendering time by the rendering unit 104 in FIG. 6 is based on a safety factor, the larger the area of the hatched portion, the more the above-mentioned safety factor is applied to the rendering process. The time must be estimated to be long. However, in the conventional technology using the safety factor,
Regardless of whether the area of the hatched portion is large or small, the safety coefficient is determined uniformly. For this reason, when a situation where the area of the shaded portion becomes large for a certain band occurs, if the rendering processing for the band is greatly delayed, there is a high possibility that a print overrun will occur.

One means for preventing print overrun is disclosed in JP-A-11-249833. According to the publication, the time required to perform the rendering process for each band is predicted, and for the band whose predicted rendering time exceeds a predetermined value, before the output unit transfers the image data to the printing unit, That is, the rendering process is executed before printing is started, and if the band is within a predetermined value, the rendering process is executed simultaneously with the printing process of the printer engine, so that the print overrun is reliably prevented. And That is, the third band memory is provided.

However, this method does not execute the pre-rendering process in consideration of the frequency of contention for access to the physical memory, but simply executes the band rendering process in which the time required for rendering is expected to exceed a predetermined value. This is executed before printing is started to prevent print overrun. For this reason, rendering of a band that is within the predetermined value and as close as possible to the predetermined value or the like may cause print overrun in a situation where the shaded area shown in FIG. 6 is large. Conceivable. This is because the time required for rendering is predicted independently of the frequency of contention for access to the physical memory, and the band to be pre-rendered is set based on a predetermined value which is also set independently of the frequency of contention for access to the physical memory. It is because it has been determined.

Another means for preventing a print overrun is disclosed in Japanese Patent Application Laid-Open No. H11-198462. In this publication, in order to efficiently execute band processing with a minimum memory capacity, a rendering schedule is created before the printer engine starts operation, and rendering and output of each band are executed based on the schedule. The method is shown. However, the publication also states that
In the schedule creation method, there is no mention of the frequency of access conflicts to the physical memory, and when a situation occurs where the shaded area shown in FIG. 6 is large, a print overrun still occurs. I will.

The present invention has been made under such a technical background. That is, an object of the present invention is to estimate the processing time required for the rendering process according to the length of the period during which there is a possibility that an access conflict may occur in which the rendering unit and the output unit access the same physical memory at the same time. An object of the present invention is to provide an image forming apparatus for executing a process for preventing a print overrun and an image processing method therefor.

[0022]

According to one aspect of the present invention, there is provided an image forming apparatus for recording an image by a predetermined recording method based on drawing data to be printed. Intermediate data generating means for generating intermediate data before being developed into bitmap data based on the print data, rendering means for generating bitmap data for each predetermined drawing unit based on the intermediate data, A plurality of physical memories that store bitmap data generated by the means and that can be accessed independently of each other; and a plurality of bands that are allocated in the plurality of physical memories and store the bitmap data generated by the rendering means. A memory, wherein the rendering means determines bitmap data for each predetermined drawing unit based on the intermediate data; Rendering time estimating means for estimating the time required for generation, output means for transferring recording data from the plurality of physical memories to the printing unit in synchronization with the operation of the printing unit, and printing for the printing unit. A safety coefficient storing means for storing a safety coefficient serving as an index for estimating the required time longer than the actual time, wherein a period during which the rendering means and the output means may access the physical memory may overlap. And the rendering time estimating means performs pre-rendering for a band whose time obtained by prediction using the safety coefficient exceeds a predetermined value.

According to a second aspect of the present invention, in an image processing method of an image forming apparatus for recording an image by a predetermined recording method based on drawing data to be printed, the image processing method develops bitmap data based on the input print data. An intermediate data generating step of generating intermediate data before being performed, a rendering step of generating bitmap data for each predetermined drawing unit based on the intermediate data, and a step of the rendering unit performing predetermined drawing based on the intermediate data. A rendering time estimation step of estimating the time required to generate bitmap data for each unit, and a safety coefficient storing a safety coefficient serving as an index for estimating the time required for printing by the printing unit longer than the actual time are obtained. And the bitmap data generated in the rendering step is stored in a physical memory. The security factor is changed according to a period in which access for storage and access for reading the bitmap data stored in the physical memory by the printing unit may overlap, and the rendering time prediction is performed. Pre-rendering is performed for a band whose time obtained by predicting using the safety coefficient in the process exceeds a predetermined value.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. Here, a case will be described in which the image forming apparatus and the image processing method of the present invention are applied to an ink jet printer, but the present invention is not limited to an ink jet printer.
The present invention can be applied to a thermal transfer printer, a laser printer, and a wire dot impact type printer.

FIG. 7 is a block diagram showing the configuration of the image forming apparatus of the present embodiment. In the figure, reference numeral 203 denotes an external interface (I / F) for connecting the external device 201 and the image forming apparatus 202. Reference numeral 204 denotes a CPU that controls the entire apparatus, and 205 denotes a CPU 2
04 is a ROM that stores a basic program in a processing procedure to be executed. A RAM 211 includes a work area 211a to which the CPU 204 refers when executing various processes, a reception buffer area 211b which is a temporary storage area for received PDL data, and an intermediate language area 211c for storing intermediate data. And a temporary memory area 211d for storing bitmap data of the band to be pre-rendered.

An emulation program memory 206 stores an emulation program for interpreting various printer languages, and is constituted by a ROM in this case. Reference numeral 207 denotes an intermediate language generation library memory that stores a collection of various functions related to the generation of a dot pattern. Reference numerals 212a and 212b denote font scaler memories that enable printing of a plurality of types of characters (for example, Gothic font, Mincho font, etc.). The contents of the font data stored in the font scaler memories 212a and 212b are outline font data of each character type and a program for generating a final character pattern based on the data. In this example, the font scaler memories 212a and 212b are also RO
M.

An area for the band memories 1 and 3 is secured inside the first physical memory 213a, and an area for the band memories 2 and 4 is secured inside the second physical memory 213b. Is secured. The first physical memory 213a and the second physical memory 213b are
Each is separately connected to the system bus 215,
Can be accessed independently. Reference numeral 208 denotes a nonvolatile memory which stores various setting contents, and is constituted by an EEPROM in this case.

Reference numeral 209 denotes an RS conversion unit. The RS conversion unit 209 reads the bitmap data from the first physical memory 213a and the second physical memory 213b, converts the bitmap data into an RS (raster / slice), and converts the data into an SRAM 214.
a, 214b, and then transfer the image data from the SRAMs 214a, 214b to the printing unit 216 via the output interface 210 in synchronization with the operation of the printing unit 216. The RS conversion unit 209 is configured by a custom IC such as an ASIC here.

FIG. 8 is a diagram conceptually showing a part of the block diagram shown in FIG. 7 and the flow of image data. FIG.
Among them, the portions corresponding to the components shown in FIG. 7 in one-to-one correspondence are denoted by the same reference numerals. Here, as shown in FIG. 8, a case will be described in which an image for one page is divided into nine bands and band processing is performed.

The input unit 331 mainly corresponds to the external interface (I / F) 203 shown in FIG. Output unit 34
4 is an output interface (I / F) of FIG.
210. The print data received by the input unit 331 is sent to the intermediate data generation unit 332, and is converted into intermediate data. Here, the “intermediate data” is data located at an intermediate position between high-dimensional print data and low-dimensional bitmap data, and is a PDL (Page Description Language).
Is high-dimensional print data (PDL data) such as image data converted so as to be easily developed into bitmap data. The function corresponding to the intermediate data generation unit 332 is performed by the CPU 204 and the intermediate language generation library memory 207 in FIG.

In the safety coefficient storage unit 335, several levels of safety coefficients are set according to the time length of competing band processing. The rendering unit 334 acquires an appropriate value of the safety coefficient from the safety coefficient storage unit 335 based on the length of time. The function of the rendering unit 334 is mainly performed by the CPU 204 of FIG. 7, and the function of the safety coefficient storage unit 335 is mainly performed by the nonvolatile memory 2 of FIG.
08 plays.

The intermediate data for one page generated by the intermediate data generation unit 332 is stored in the intermediate data storage unit 333.
Temporarily, and finally, the rendering unit 334
Sequentially reads this data and develops it into bitmap data. Note that the intermediate data storage unit 333 stores the
Corresponding to the intermediate language area 211b in the RAM 211.

Before performing the rendering process, the rendering unit 334 first stores the intermediate data storage unit 333.
, The rendering time of each band is predicted based on the estimated rendering time of each band, and the rendering process and the output process of each band are simulated based on the predicted rendering time of each band. It is assumed that the result of the simulation is as shown in FIG. 6, for example. In the case of FIG. 6, as described above, there is a high possibility that the access for the rendering process and the access for the output process conflict in the hatched portion. From this result, it is checked whether or not access for rendering processing and access for output processing to the same physical memory conflict with each other, and if so, which band processing conflicts is determined.

Then, based on the result, the corresponding safety coefficient is obtained from the above-described safety coefficient storage unit 335, and the time required for rendering for each band is predicted again based on the obtained safety coefficient. The value is compared with a predetermined value set in advance. FIG. 9 is a band graph in which the predicted value is shown by taking time on the vertical axis, and the predetermined value indicated by the dotted line is set in advance. In the graph, the solid band graph shows the time required for the rendering process predicted independently of the safety coefficient, and the hatched band graph shows the time required for the rendering process predicted based on the number of safety cases. I have.

FIG. 9 shows that the number of bands exceeding a predetermined value changes depending on whether or not a safety coefficient is introduced. It can also be seen that if the value of the safety coefficient changes, the height of the shaded band graph in FIG. 9 changes. Pre-rendering is performed before the actual printing operation is started for a band in which the estimated rendering time obtained by introducing this safety factor exceeds a predetermined value, and rendering for other bands is performed. , In parallel with the output process, that is, in parallel with the image forming process of the printing unit 210.

In the present embodiment, as described above, the predicted time in consideration of the safety coefficient is compared with a predetermined value, and for a band exceeding the predetermined value, pre-rendering is performed prior to the entire rendering processing. By doing so, print overrun is prevented. In this case, in order to realize efficient band processing, it is important to appropriately determine the above-described safety coefficient and a predetermined value.

In the present embodiment, the safety coefficient is determined by the external device 2
01 can be changed for each page of the PDL data sent from the server. For this purpose, some safety factors are stored in advance in the safety factor storage unit 335, and the safety factor optimized for the image data to be rendered by the rendering unit is obtained from the safety factor storage unit 335. Then, the CPU 204 determines a band to be pre-rendered based on the safety coefficient.

The function of the safety coefficient storage unit 335 is performed by the nonvolatile memory 208 shown in FIG. That is, in the nonvolatile memory 208, a safety coefficient corresponding to the ratio calculated in the above process is set in advance as a look-up table as shown in FIG. 10, and the CPU 204 refers to this as necessary. . As shown in FIG. 10, the look-up table is set so that the larger the ratio of the hatched area shown in FIG. 6, the larger the safety coefficient. That is, the setting is made such that the larger the ratio of the shaded area, the slower the estimation of the rendering process of the CPU 204. The numerical value of the safety coefficient shown in FIG. 10 represents the ratio of estimating the rendering process late, as a percentage. For example, when the safety coefficient is “10”, it means that the time required for rendering is estimated to be 110% of the estimated rendering time without considering the safety coefficient.

For the band to be pre-rendered,
The temporary memory 211d is used for storing the bitmap data obtained as a result, and the first physical memory 213a and the second physical memory 2 are used for rendering other bands.
13b is used. Each physical memory has two areas (band memory areas) for storing bitmap data generated by the rendering unit 334 in band units. That is, the band memories in the first physical memory 213a are the band memories 1 and 3, and the band memories in the second physical memory 213b are the band memories 2 and 4. On the other hand, in the temporary memory 211d, the capacity required for the number of bands to be pre-rendered by the rendering unit 334 is equal to the RAM 21 in FIG.
1 is reserved and used.

In this embodiment, the rendering unit 334 determines the band to be pre-rendered based on the security coefficient that can be changed in page units as described above. Even in the case where the contention between access and access from the output unit 344 frequently occurs, print overrun can be prevented. In addition, the external device 20
The band to be subjected to the pre-rendering process is appropriately determined in accordance with the PDL data sent from No. 1, and the physical memory can be used efficiently.

Next, the data flow will be described with reference to the block diagram shown in FIG. The PDL data transmitted from the external device 201 is first stored in the reception buffer area 211b in the RAM 211 via the external interface 203. When the PDL data is stored in the reception buffer area 211b, the CPU 204
An emulation program for analyzing the DL data and developing it into intermediate data is called from the emulation program memory 206, and intermediate data is generated based on the PDL data. When one page of intermediate data is generated, it is stored in the intermediate language area 211c.

In the process of generating the intermediate data, the CPU 204 estimates and accumulates the time required for rendering the intermediate data corresponding to each band (required rendering time). The method of deriving the required rendering time differs depending on the type of the intermediate data, and is roughly classified into three methods. The first method is a case where a rendering time peculiar to the intermediate data is fixedly determined. In this case, the rendering time is read from the contents stored in the table in advance. The second method is that if the intermediate data is, for example, an image bitmap, and the content of the rendering process is a copy of a simple memory content, the rendering time is simply determined by the size of the intermediate data. Is a method of deriving the rendering time from the data size. The third method is a case of intermediate data for which the rendering time is not known unless the rendering is actually performed. For such data, the rendering process is actually executed to determine the rendering time.

When characters, tables, graphics, and the like are mixed in an image for one page, there is a possibility that the first, second, and third methods described above are mixed in each band. .
Therefore, when estimating the required rendering time, the required rendering time is estimated and calculated for each unit of the intermediate data (for each drawing object), and the estimated required rendering time is accumulated for each band. go. The rendering time thus obtained is stored in the work area 211a of the RAM 211 as information for each band.

Next, the CPU 204 first executes a simulation as shown in FIG. 6 based on the estimated rendering time required for each band and the image forming processing speed of the printing unit 216. 6, that is, the rendering process of the CPU 204 is performed by the RS conversion unit 209.
Calculates the accumulated time of the time delayed by the interrupt of
The ratio of rendering the image data for one page in the period corresponding to the shaded area for one page is calculated, and the lookup table set in the nonvolatile memory 208 is referred to as described above.

Next, the CPU 204 determines whether or not the rendering time estimated in this way exceeds a predetermined value set in advance. This predetermined value is set in the nonvolatile memory 208 in advance. That is, the CPU 20
4 compares the predetermined value with the predicted rendering time estimated as described above, and for a band for which it is determined that the predicted rendering time exceeds the predetermined value,
Pre-rendering processing is performed, and the information is stored in the work area 211a of the RAM 211. Before starting the operation of the printing unit 216, the work area 2
Based on the information stored in 11a, pre-rendering is performed for a predetermined band, and bitmap data generated in the process is stored in a temporary memory area 211d. When the pre-rendering process ends, the CPU
204 and the RS conversion unit 209 sequentially execute normal band processing for the other bands.

FIG. 11 is a flowchart showing a processing schedule obtained by performing the above-described processing. In FIG. 11, the pre-rendering process is executed for band 2 and band 5. As can be seen by comparing FIG. 11 with FIG. 6, in the case of FIG. 11, the hatched portion in which access to the physical memory competes is smaller than in the case of FIG. 6, and therefore, it is possible to effectively prevent print overrun. I understand.

The embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment, and various modifications may be made within the scope of the invention described in the appended claims. Is possible.

[0048]

As described above, the safety factor is converted in consideration of the delay time of the rendering process which occurs to avoid contention for access to the physical memory. In other words, the physical memory of the rendering means and the output means is converted. The security factor is changed in accordance with the period in which access to may be duplicated, and for a band in which the time obtained by the rendering time estimating means using the safety factor and predicted exceeds a predetermined value, pre-rendering is performed. As a result, even if the delay time generated to avoid contention for access to the same memory between the rendering unit and the output unit that transfers the bitmap data to the printing unit increases, print overrun is reliably prevented. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall flow of data of a conventional image forming apparatus.

FIG. 2 is a schematic block diagram of a conventional image forming apparatus.

FIG. 3 is a diagram showing a data flow in band processing of a conventional image forming apparatus.

FIG. 4 is a flowchart illustrating processing performed by a conventional image forming apparatus.

FIG. 5 is a diagram showing a data flow when band processing is performed by securing two band memory areas in one physical memory.

FIG. 6 is a flowchart showing how band processing is performed when the waiting time for rendering is eliminated.

FIG. 7 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.

8 is a diagram conceptually showing a part of the block diagram shown in FIG. 7 and a flow of image data.

FIG. 9 is a band graph showing a predicted value of a time required for rendering in consideration of a safety coefficient.

FIG. 10 is a diagram showing the contents of a look-up table set so that the safety coefficient changes according to the ratio of the shaded area.

FIG. 11 is a flowchart of band processing after a schedule is reconfigured by the method of the present embodiment.

[Explanation of symbols]

201: external device (host), 202: image processing device, 203: external interface (I / F),
204 ... CPU, 205 ... ROM, 206 ...
Emulation program memory, 207: library memory for generating an intermediate language, 208: non-volatile memory, 209: RS converter, 210: output interface, 211: RAM, 211a: work area, 211b: reception buffer area,
211c: Intermediate language area, 211d: Temporary memory area, 213a: First physical memory, 213
b: second physical memory, 216: printing unit, 33
1 input unit, 332 ... intermediate data generation unit, 33
3 intermediate data storage unit 334 rendering unit
335: safety coefficient storage unit, 344: output unit

Claims (2)

[Claims] 1. An image forming apparatus for recording an image in a predetermined recording method based on drawing data to be printed, comprising: an intermediate unit for generating intermediate data before being developed into bitmap data based on input print data; A data generation unit, a rendering unit that generates bitmap data for each predetermined drawing unit based on the intermediate data, and a plurality of physical units that store bitmap data generated by the rendering unit and that can be accessed independently of each other. A memory, a plurality of band memories secured in the plurality of physical memories, and a plurality of band memories for storing bitmap data generated by the rendering means; and the rendering means for each predetermined drawing unit based on the intermediate data. A rendering time estimator that estimates the time required to generate bitmap data An output unit for transferring recording data from the plurality of physical memories to the printing unit in synchronization with an operation of the printing unit; and an index for estimating a time required for printing by the printing unit longer than the actual time. Safety factor storing means for storing a safety coefficient, wherein the rendering time is changed in accordance with a period in which the rendering means and the output means may access the physical memory in an overlapping manner; An image forming apparatus characterized in that a pre-rendering is performed for a band in which the time obtained by the prediction means using the safety coefficient exceeds a predetermined value. 2. An image processing method for an image forming apparatus for recording an image in a predetermined recording method based on drawing data to be printed, wherein the intermediate data before being developed into bitmap data based on the input print data. Generating a bitmap data for each predetermined drawing unit based on the intermediate data; and generating a bitmap data for each predetermined drawing unit based on the intermediate data. A rendering time prediction step of predicting the time required to generate the image, and a step of obtaining a safety coefficient storing a safety coefficient serving as an index for estimating the time required for printing of the printing unit longer than the actual time. The bitmap data generated in the rendering step is stored in a physical memory. The security factor is changed in accordance with a period in which the access and the access for reading the bitmap data stored in the physical memory by the printing unit may overlap with each other. An image processing method for an image forming apparatus, comprising: performing pre-rendering for a band whose time obtained by prediction using a coefficient exceeds a predetermined value.