JP2000168170A - Blank paper-detecting apparatus and image-recording apparatus, image-forming apparatus and image-reading apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blank paper-detecting apparatus which can detect a blank paper in a short process time. SOLUTION: Image data input through a host interface circuit 3 is temporarily stored in a page memory 5a of a RAM 5. The data is then read out from the page memory 5a, compressed by a compressing/expanding part 7 and stored again in a predetermined area of the RAM 5. At this time, the compressed data is inspected as to whether it is a blank page or a blank band. This inspection is carried out by analyzing the compressed data by an algorithm or comparing with blank page compressed data or blank band compressed data held in a ROM 6 beforehand. A volume of data after compressed is small as compared with a volume of data before compressed and therefore the inspection for the blank page or blank band can be conducted in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus such as a printer, an image reading apparatus such as a scanner, and a blank sheet detecting apparatus such as an image forming apparatus, and more particularly, to whether or not image data of an area having a predetermined size is blank. The present invention relates to a blank sheet detecting device capable of detecting a short time and accurately.

[0002]

2. Description of the Related Art Conventionally, various methods for determining a blank page have been proposed.
No. 66, and Japanese Patent Application Laid-Open No. 5-127449 (first prior art). In this prior art, for example, all the bit information of one page is inspected, and when all the bit information is 0 (white), it is determined that the page is blank.

A second prior art is disclosed in, for example,
No. 2,820,055. In this prior art, it is determined whether or not the minimum rectangular area for each piece of drawing information overlaps the print area. If all the pieces of drawing information do not overlap the print area, it is determined that the sheet is blank.

A third prior art is described in, for example, Japanese Patent Application Laid-Open No. Hei 9-149176. In this prior art, scanned image data is converted into text data, and the text data is inspected. If there is no character code, it is determined that the data is blank.

[0005]

However, in the first prior art, it is necessary to check whether or not all the bits of one page are 0, and the resolution has recently been increased. Therefore, the number of bits per page is increasing, and there is a problem that a large processing time is required for blank sheet inspection. In the case of a color image, there is page information for four colors of cyan, magenta, yellow, and black, so that there is a problem that a longer processing time is required as compared with a monochrome image.

In the second and third prior arts, 1
When the drawing information per page is small, the efficiency of blank sheet detection is high, but the processing time increases in proportion to the number of image information, and thus there is a problem that a large processing time is required depending on the content of drawing. .

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems of the prior art, and to provide a blank sheet detecting device capable of detecting a blank sheet in a short processing time, and an image recording apparatus using the same.
An object of the present invention is to provide an image forming apparatus and an image reading apparatus.

[0008]

In order to achieve the above-mentioned object, the present invention provides a blank page detecting apparatus for detecting blank page data from input image data, comprising: means for compressing the image data; It is characterized in that there is provided a blank sheet determining means for determining whether or not the data is blank data using the data compressed by the means.

According to this feature, the data amount after compression is generally smaller than the data before compression, so that the amount of calculation for determining whether or not the data is blank data is reduced. For this reason, a blank page can be detected in a short processing time.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a main part of an image recording apparatus to which a blank sheet detecting device of the present invention is applied. In FIG. 1, a CPU 1 has a central function of various controls of the image recording apparatus, and is connected to the following various circuit devices via a CPU bus 2. The host interface circuit 3 is a circuit for interfacing with a host device 4 such as a host computer, and has a circuit configuration for receiving print data input from the host device based on the RS232C standard or Centronics. I have. Further, the host interface circuit 3 may be connected to a network and supplied with print data from a plurality of devices (workstations or the like) on the network (such as Ethernet).

A RAM 5 is a working memory, and functions as a receiving buffer for temporarily storing data necessary for the image recording apparatus to perform various controls and print data input from the host interface circuit 3. . The RAM 5 includes a page memory 5a. The ROM 6 is a memory for storing a program for controlling the image recording device. The compression / expansion unit 7 compresses the bitmap information of one page, stores it in, for example, the RAM 5, decompresses it at the time of printing, and outputs it to the recording unit interface circuit 9.

The character pattern memory 8 is a so-called font memory, and stores character patterns for printing out. The recording unit interface circuit 9 converts the data decompressed by the compression / decompression unit 7 into raster data and supplies the raster data to the recording unit 10 or the recording unit 1
Between 0, various signals (synchronization pulse, status signal of the recording unit, operation command signal to the recording unit, etc.) are transmitted and received, and the interface functions as an interface between the image recording apparatus and the recording unit 10. . The recording unit 10 is composed of, for example, a laser printer.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. 2 and FIG. FIG. 3 is a diagram showing the flow of image data. In step S1 of FIG. 2, drawing information is input from the host computer 4 or the like via the host interface circuit 3. In step S2, a drawing process is performed and the image data (bitmap data) is stored in the page memory 5a of the RAM 5, for example (FIG. 3). In step S3, it is determined whether or not the input of the drawing information has been completed. If the determination is negative, the process returns to step S1 to continue the input of the drawing information.

When the input of the drawing information is completed in step S3, the process proceeds to step S4, and the creation of one page of image data is completed. Next, proceeding to step S5, in order to reduce the storage capacity of the image data, the image data is read from the RAM 5, and then compressed by the compression / expansion unit 7 (FIG. 3). move on. In step S6, the compressed data is temporarily stored in the RAM 6 (FIG. 3).

In the present invention, in step S7, a blank page is detected from the compressed data. In other words, the compressed data is analyzed from the compression algorithm,
Judge whether it is a blank page or not. For example, in the case of the compression technique of an algorithm for converting to the compressed data of “how many bits of 0 or 1 continue when the same bit continues”, blank paper “00FF, 00FF,.
Assuming that the compressed data is "FF" (where F = 1111), in step S6, the compressed data of one page is analyzed, and the compressed data is stored in "00" from the beginning to the end.
FF ”is determined. And "00FF"
It is determined that the sheet is not blank when it is no longer. If it is "00FF" until the end, it is determined that the sheet is blank. Note that R
Instead of using the compressed data temporarily stored in the AM 6, the data compressed in step S5 may be directly used to determine blank paper.

In step S8, the result of the blank sheet detection in step S7 is stored in the RAM 5. In addition,
When it is determined that the data is blank, the compressed data obtained by the compression process may be replaced with predetermined one-page white compressed data stored in the ROM 6 and stored. Further, a flag indicating that one page is blank may be set in the RAM 5.

Next, when the recording operation starts, step S9 is performed.
Then, the compressed data read from the RAM 5 is expanded, and the expanded data is sent to the recording unit interface circuit 8 (in FIG. 3). Note that the compressed data in which one page is blank may be read directly from the ROM 6 to the compression / decompression unit 7. In step S10, the decompressed data is converted into raster data by the recording unit interface circuit 8, sent to the recording unit 10, and recorded on paper. As for printing on the blank paper, the compressed data may be expanded and printed as described above, or the printing process and the paper discharging process may be omitted so that printing is not performed.

As described above, according to the present embodiment, blank pages are detected by using compressed data, so that all bits before compression are inspected and determined to be blank as in the related art. Obviously, the amount of data to be inspected is greatly reduced, and the blank page detection time is much shorter.

Next, another embodiment of the blank page detection will be described. In this embodiment, compressed data for blank paper is prepared in advance in the ROM 6 or the like for each paper size to be printed, taking into account the paper direction, resolution, and the like. And
The image data compressed in step S5 is compared with the compressed data of the blank sheet having the same paper size, direction, and resolution as the image data. If the two compressed data match, it is determined that the page is blank, and if they do not match, it is determined that the page is not blank. The comparison of the compressed data may be performed by software or hardware. If performed by hardware, the load on the CPU 1 can be reduced.

In general, since the size of compressed data is significantly reduced, even if the compressed data is compared with each other as described above, it is difficult to compare all the bits before the conventional compression. As compared with, the time for detecting a blank sheet is much shorter.

Next, another embodiment of the present invention will be described.
This embodiment divides an image of one page into a plurality of bands a to g as shown in FIG.
6, the compressed data A when the band is entirely white is held, and if there is a blank band, the compressed data A is used as the compressed data of the band.
If the band is not a blank band, for example, the band d, the compressed data d is stored in a predetermined area of the RAM 5.

Next, the operation of this embodiment will be described in detail with reference to the flowchart of FIG. Step S1
In step 1, one band is drawn, and the process proceeds to step S12.
Then, this is compressed. In step S13, it is detected whether or not the band is blank. As described above, this detection may be performed by analyzing the compressed data, or may be compared with blank band compressed data. In step S14, it is determined whether or not the band is blank. If the band is not blank, the process proceeds to step S15, and the compressed data is stored in the RAM 5. On the other hand, if the band is blank, the process proceeds to step S16, and blank information (for example, a flag) indicating that the band is blank is stored in the RAM 5. Note that the blank page compression information on the ROM 6 may be transferred to the RAM 5 and stored in the RAM 5.

In step S17, it is determined whether or not the compression processing of all the bands of one page has been completed. If the determination is affirmative, the process proceeds to step S18. When the process proceeds to the printing process, the compression information of one band is read from the RAM 5 in step S18, and the compression / expansion unit 7 performs the expansion process in step S19. In this expansion process, the expansion data for the blank band may be expanded using the blank compression information stored in the ROM 6. In step S20, it is determined whether or not the expansion processing of all the bands of one page has been completed. If the determination is affirmative, the process proceeds to step S21, where the expanded data is converted into raster data by the recording unit interface circuit 9. Then, it is sent to the recording unit 10 and recorded on a sheet.

According to this embodiment, a blank page can be detected at a high speed even in the case of a technique of dividing an image of one page into a plurality of prints, that is, in the case of banding.
Further, for a blank band, it is only necessary to set a bit indicating that the band is blank at a predetermined position in the RAM 5, so that the used area of the storage area of the RAM 5 can be reduced.

In each of the above embodiments, it is preferable that the compressed data of one page or one band of blank paper is stored in the ROM 6. However, whether the compressed image data is a blank page or blank band is determined. When confirming the above or when using as blank compressed data at the time of decompression, the blank compressed data may be read directly from the ROM 6 or may be stored in the RAM 5 once before use.

In the case where the blank compressed data is directly read from the ROM to determine whether or not the blank page or blank band is used, or when the compressed data of the blank page or blank band is used as the compressed data in the expansion, There is no need to write blank compressed data in RAM in advance,
In addition, it has a merit that the RAM area is not consumed, but has a demerit that the reading speed of the compressed data is slow.

On the other hand, when the blank compressed data is once stored in the RAM and then used, the advantage is that the access speed to the RAM is high, and the determination as to whether or not the blank page or blank band is made faster. Have. However, when the compressed data is read from the RAM, the data is transferred by DMA (Direct Memory Access), but it is necessary to match the RAM with the cache memory of the CPU before the DMA transfer. Since this alignment operation is performed by the CPU, there is a disadvantage that some load is imposed on the CPU.

The present invention can be applied not only to the above-described image recording apparatus but also to an image reading apparatus or an image forming apparatus.

[0029]

As is apparent from the above description, according to the present invention, it is determined whether or not a sheet is blank using the compressed image data. The amount of data to be inspected can be significantly reduced as compared with the conventional case. Therefore, the processing time for determining that the sheet is blank can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an image recording apparatus to which the present invention is applied.

FIG. 2 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a data compression / expansion operation according to the embodiment;

FIG. 4 is an explanatory diagram of compression / expansion processing of image data including a blank band.

FIG. 5 is a flowchart illustrating an operation of a compression / expansion process of image data including the blank band.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... CPU, 2 ... CPU bus, 3 ... Host interface circuit, 5 ... RAM, 6 ... ROM, 7 ... Compression / expansion part, 8
... Character pattern memory, 9 ... Recording unit interface circuit, 10 ... Recording unit.

Claims (10)

[Claims] 1. A blank page detecting device for detecting blank page data from input image data, comprising: means for compressing the image data; and using the data compressed by the compressing section to determine whether the data is blank page data. A blank sheet detection device, comprising: 2. The blank page detection device according to claim 1, wherein the blank page determination unit determines whether or not one page or a band obtained by dividing the one page is blank page data. White paper detection device. 3. The blank page detection device according to claim 1, wherein the blank page determination unit analyzes the compressed data to determine whether the data is blank page data. apparatus. 4. The blank page detection device according to claim 1, wherein the blank page determination unit compares the compressed data with compressed data of a blank page stored in advance, and determines blank page data. A blank sheet detection device, which determines whether or not a blank sheet is detected. 5. The blank paper detecting apparatus according to claim 4, wherein the previously stored blank compressed data is blank compressed data for each output paper size or each band size. Detection device. 6. The blank sheet detecting device according to claim 4, wherein the compressed data of the blank sheet is stored in a ROM. 7. The blank page detecting device according to claim 6, wherein the compressed data of the blank page stored in the ROM is temporarily stored in the ROM.
A blank sheet detection device developed and used on an AM. 8. An image recording apparatus comprising the blank sheet detecting device according to claim 1. 9. An image forming apparatus comprising the blank sheet detecting device according to claim 1. 10. An image reading apparatus comprising the blank sheet detecting device according to claim 1.