JP2852029B2 - Image processing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method for setting a correction table corresponding to the characteristics of an image input / output device in the image input / output device. 2. Description of the Related Art In recent years, with the development of image processing technology by computers, creation, editing, storage, etc. of images such as printed matter have been performed by computers. Generally, in such an image, one pixel is represented by one bit of 0 or 1. Such an image is called a binary image. On the other hand, images of characters, figures, etc.
A good image can be obtained by converting to a value, but in an image such as a photograph which requires halftone expression, halftone is expressed by giving 4 to 8 bits to one pixel. This is called a multi-valued image. FIG. 1A shows an original image expressed in halftone and an example (b) obtained by binarizing the original image with a threshold value of 1/2, that is, 8 in the case of 16 gradations. For one pixel, 1 bit represents black and 1 represents white. FIG.
In the diagram schematically illustrating the valued image, it is depicted as one block per pixel. In this case, it is represented as planar two-dimensional information with Z = 1. FIG. 1D is a diagram showing the original image (a) as multi-valued data of 16 gradations of density levels 0 to F. FIG. 1E schematically illustrates image information represented by multi-valued data. One pixel has four blocks, that is, four bits of information. Although the binary image and the multi-valued image have been described above, devices such as a printer or a display connected to the image processing system are conventionally fixed in the system, and the input-output characteristics of the device are conventionally fixed. That is, the main body fixedly performs γ correction on image information based on γ characteristics. This is a significant factor, especially when dealing with multi-valued images. More specifically, the data from the TV camera is γ-matched to the data in accordance with the γ characteristic fixedly possessed by the CRT so that the data can be seen well on the CRT display.
Correction has been performed. However, when the data from the TV camera is printed as it is, since the data does not match the γ characteristic unique to the printer, the printer output becomes, for example, a blurred image without contrast. In this case, an appropriate output image can be obtained by performing gamma correction in accordance with the gamma characteristic unique to the printer. However, in practical use, there is a possibility that the devices connected to the system may be changed in various ways.
Therefore, resetting the optimum γ correction data according to the changed device every time the device is changed greatly gives a user an additional effect. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has an object to be able to set a correction table according to the characteristics of a connected image input / output device without imposing a load on a user. With the goal. In order to achieve the above object, the present invention provides an image processing method applied to an image processing device connected to an image input / output device via a communication path. The image input / output device is recognized, and a correction table corresponding to the result of the recognition is read from a storage unit that stores a correction table corresponding to the characteristics of the plurality of image input / output devices. The read correction table is set in the image input / output device so that a correction process suitable for the output device can be performed. FIG. 2 is a system block diagram of one embodiment of the present invention. As a gradation image input device, there are a CCD scanner 1 for photoelectrically converting and inputting a document image by a one-dimensional CCD array, and a still video (SV) camera 11 for inputting a three-dimensional image by a two-dimensional CCD array.
A laser printer 2 and a CRT 7 that perform gradation expression by pulse width modulation and electrophotography as a gradation image output device. The system also includes a central processing unit (CPU).
4, memory for storing programs or image data 5, C
A frame buffer 6 for storing an image to be displayed on the RT 7;
A keyboard 8 which is an input device of an operator, a disk 10 for storing programs and image data described below and a disk interface 9 for connecting the disk, and a scanner for connecting the CCD scanner 1 and the printer 2 Printer interface 3, SV camera 1
1 is connected to an SV camera interface 12 for connection. Referring to FIG. 2, the flow of data in each section will be described with reference to an example in which a document image is input, subjected to image processing, and then output to a printer. First, the gradation image data converted into an electric signal by the CCD scanner 1 is taken into the system via the SP-I / F 3 and stored in the memory 5 as multi-valued digital data. This image can be transferred to the frame buffer 6 and monitored by the CRT 7.
When the operator views the monitored image and gives an instruction for necessary image processing using the keyboard 8, the CPU 4 executes the image processing. The image processing here may be any processing such as image cutting, edge enhancement, density conversion, and contrast conversion. At the time of image output, the image data on the memory 5 is again output to the laser printer 2 via the SP-I / F3. Here, both the CCD scanner 1 and the laser printer 2 are scanning type document input / output devices, and the interface can be shared. Further S
By making it possible to connect a scan and a printer in the SP-I / F3 by devising the PI-I / F3, it is possible to copy a document directly without taking in image data into the system. . This makes it possible to perform a copying operation using a scanner and a printer even while the system is executing other processing, thereby increasing the use efficiency of the image input / output device. FIG. 3 shows a state transition diagram representing online / offline. FIG. 3 is a state transition diagram showing online / offline, which comprises three modes: an idle mode, an online mode, and an offline copy mode. After power-on, it enters the idle mode, and enters the online mode by the online instruction. In the online mode, image data is exchanged between the scanner and the printer and the host computer, and the mode returns to the idle mode upon return. In addition, an offline copy mode is entered from the idle mode by an offline copy instruction. In the offline copy mode, the scanner and printer are directly connected and the copy operation is performed.
Return to idle mode by return instruction. The problem here is the gradation correction (γ correction) as described above. Image input / output devices have input / output characteristics (gamma characteristics) unique to each device. FIG. 4A shows input / output characteristics of a laser printer as an example. When an image is output, tone correction (gamma correction) including the input system and output system is required. However, when image data is loaded into the system and processed at the same time,
Correct processing cannot be performed unless processing is performed with linear data (γ = 1) that does not depend on the characteristics of the input / output device as much as possible. Next, the input / output characteristics of the printer shown in FIG. 4A and the gradation correction .gamma. Table stored in the gradation correction circuit 16 shown in FIG. FIG. 4B shows an example of the gamma correction table. In the printer shown in FIG. 4A, it is assumed that the γ characteristic is a or b. If the input level is, for example, A1, as shown in FIG.
4, which is almost black. For the user, if the input is A1, for example, if the γ characteristic is b, and if the output density is A3, it is assumed that the image is appropriate. In this case, the gamma correction table is designed so that when A1 is input, the output level of A2 can be obtained based on the curve of b '. As a result, the output can be properly and almost linearly obtained with respect to the input in the printer. FIG. 5 shows a circuit for specifically realizing gradation conversion. Reference numeral 1 denotes a CCD scanner, a CCD driver 14 for converting light intensity into an electric signal by photoelectric conversion, a shading correction circuit 15 for correcting a light intensity difference between a central portion and an end portion of the CCD array, and a correction table for γ or the reverse. And a synchronizing circuit 17 for controlling the timing of the input system. Reference numeral 2 denotes a laser printer, a pulse width modulation circuit 19 for converting gradation data into a pulse width, a laser driver 18 for controlling ON / OFF of a laser, and a synchronization circuit 2 for controlling timing of an output system.
Consists of zero. Reference numeral 3 denotes a switch 27 for switching online / offline by an SP-I / F or a gamma or a tone correction circuit 21 having a correction table for the reverse, a synchronizing circuit 23 for synchronizing with an input / output device, an input / output system and a system. And a buffer 22 for transferring data of
SP-1 / F3 is connected to system bus 13 via. Therefore, according to the present invention, when the copying operation is performed off-line, the correction including the input system and the output system is performed by the gradation correction table in the gradation correction circuit 16 in the scanner (connection A- of the switch 27). C) When inputting online, the scanner switches the gradation correction table in the gradation correction circuit 16 in the scanner, corrects only the input system (reverse correction of γ) (switch connection AB), Γ = data
Incorporated as 1 into the system. Further, when outputting from the system, the interface (in the gradation correction circuit 2 in FIG. 4)
In 1), the gradation correction table is switched to perform gradation correction only for the output system (switch connection CD). FIG. 6 shows a processing flow in the on-line mode. After entering the on-line mode by an on-line instruction by an operator's key operation or the like, an on-line instruction is issued to the scanner 1 to put the scanner in the on-line mode.
At this time, the scanner 1 switches the gradation correction table online as described in FIG. 5 (S1). next,
The switch circuit 27 in SP-1 / F is set to online A-
Switching to B and CD enables input / output between the host and the scanner 1 and the printer 2 (S2). After that, scanner 1
After waiting for a read command from the printer or a print command to the printer 2 (S3), input / output is executed (S4). When the online processing is completed (S5), the mode returns to the idle mode with a return instruction. FIG. 7 shows a processing flow in the off-line copy mode. After entering the off-line copy mode by the off-line copy instruction, an off-line copy instruction is issued to the scanner 1 to put the scanner in the off-line copy mode.
At this time, the scanner switches the gradation correction table to offline copying as described with reference to FIG. 5 (S6). Then S
The switch circuit 27 in P-1 / F is switched to off-line AC to directly connect the scanner and the printer to enable a copy operation (S7). Then, after waiting for a copy start command (S
8), a copy operation is performed (S9), and when the online copy processing is completed (S10), the mode returns to the idle mode with a return instruction. Since the printer performs the same operation in online and offline copying, it is not necessary to switch the mode of the printer. (Embodiment 2) The tone conversion (γ correction) between the scanner and the printer system (host) in online / offline in the image processing system has been described above. Is connected. FIG. 8 shows the system bus 13 shown in FIG. 2 and a plurality of printers Printer1 and Printer1 connected thereto.
2 and 3 are block diagrams of scanners (TV cameras) 1 and 2. The terminal 50 including the scanner 1 and the printer 3 is equivalent to the terminal shown in FIG. Each of the interfaces 51 to 53 provided corresponding to each printer or scanner has a γ conversion circuit. This has a table for reversely converting the γ correction table suitable for each device as shown in FIG. 4B, and sets γ = 1 based on this table. Is such that the image information of γ = 1 always flows. (Embodiment 3) In FIG. 8, a γ conversion circuit is provided for each of the interfaces 51 to 53. However, when a printer and a scanner are fixedly connected to some extent, the γ conversion circuit is used. The gamma correction table corresponding to the characteristics is stored in the disk 10 or the like shown in FIG. 2, and when the power is turned on or the terminal is connected, the attribute of each device is set to C.
The PU 4 may recognize the table information and develop the table information in the RAM in each gamma conversion circuit in FIG. The above-described gradation correction is not only a correction of the characteristic γ of the input / output device, but also the shading (level and range) of the image.
Because gradation conversion such as contrast can be realized at the same time,
The image quality can be improved by using the gradation conversion table not only for correction but also for image correction and editing. Referring to FIG. 5, when the correction is made, the gradation correction table of the SV camera is considered to be equivalent to that of the scanner, and the gradation correction of the SV camera can be realized by the gradation correction circuit in the SP-I / F. The system shown in the present embodiment is not limited to this, and may be modified from a part of the system, or may be constituted by terminals connected via a LAN, and the functions of the present invention may be modified. This includes the case where it is achieved by a single machine. As described above, according to each of the above-described embodiments, the host (system) operates directly in addition to the image input / output by directly connecting the input device and the output device of the halftone image in the interface. Inside, as a copy,
I / O devices can be used to increase the efficiency of use of I / O devices, and at the same time, online / offline
By switching the gradation correction table, data can be transferred at an appropriate gradation. Further, it becomes possible to provide an image processing system in which image information of γ = 1 always flows on the system bus irrespective of the attributes of connected devices. Further, it is possible to rewrite the gradation correction table according to the connected device. According to the present invention, an image input / output device connected to an image processing device via a communication path according to the characteristics of the image input / output device can be provided without imposing a load on the user. Correction table can be set. That is, the image input / output device can perform a correction process suitable for the image input / output device without imposing a load on the user. In addition, it is possible to eliminate the need to previously hold the correction table in each image input / output device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram in a case where an original image is represented by a binary expression or a multi-value expression. FIG. 2 is a configuration block diagram of an image processing system to which the present invention can be applied. FIG. 3 is a diagram showing online and offline state transitions. FIG. 4 is a diagram illustrating a relationship between a gamma characteristic of the printer and a gamma characteristic table. FIG. 5 is a diagram showing a specific configuration of an SP-I / F 3, a scanner 1, and a printer 2 shown in FIG. FIG. 6 is a processing flowchart in an online mode. FIG. 7 is a processing flowchart in an offline copy mode. FIG. 8 is a block diagram when a plurality of terminals are connected to the system.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yasuhisa Mobara 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (58) Field surveyed (Int. Cl. ⁶ , DB name) G06T 5/00 H04N 1/407 JICST file (JOIS)

Claims (1)

(57) [Claims] An image processing method applied to an image processing apparatus connected to an image input / output apparatus via a communication path, wherein the correction table recognizes the image input / output apparatus and corresponds to characteristics of a plurality of image input / output apparatuses. A correction table corresponding to the result of the recognition is read from a storage unit for storing the correction table. An image processing method, wherein the image processing method is set in the image input / output device.