110. The acquired scanned image to be inspected is stored in the RAM 252.

Subsequently, the inspection apparatus 150 causes the inspection processing unit 256 to perform inspection by comparing a reference image previously stored as a reference image in the RAM 252 with the scanned image of the inspection target. More specifically, the inspection processing unit 256 extracts feature points from each of the reference image and the scanned image and aligns the reference image and the scanned image based on the extracted feature points. If a difference between a pixel value (luminance value) of a pixel to be inspected in the aligned scanned image and a pixel value (luminance value) of a pixel to be compared in the reference image is less than or equal to a threshold, the inspection processing unit 256 determines that the pixel to be inspected is acceptable. The threshold is varied for each inspection level. The inspection is performed for each reference image corresponding to each scanned image.

After all of the pixels are inspected, it is determined whether the total sum of pixels determined to be unacceptable is less than or equal to an acceptance threshold and determines whether the scanned image is normal. In a case where the total sum of pixels determined to be unacceptable is less than or equal to the acceptance threshold, the inspection processing unit 256 determines that the scanned image is normal. In a case where the total sum of pixels determined to be unacceptable exceeds the acceptance threshold, the inspection processing unit 256 determines that the scanned image is not normal. A result of the inspection is stored in the RAM 252. Examples of the result of the inspection include information indicating whether the printed material has a defect, a type of the detected defect (spot and stripe), and information about the position of the defect which is displayed on the UI unit 257.

Next, the CPU 251 of the inspection apparatus 150 instructs the UI unit 257 to display the inspection result stored in the RAM 252. With the inspection result displayed on the UI unit 257, the user recognizes the inspection result. In a case where a predetermined number of defective printed materials successively occur, the CPU 251 transmits the above-described information to the inspection unit 110 via the communication I/F unit 254.

The information indicating that the printed materials with a defective successively occur is received by the control unit 210 via the communication I/F unit 214. In response to the control unit 210 receiving the above-described information, the CPU 211 transmits the above-described information to the image forming apparatus 100 via the accessory I/F unit 215. The above-described information is received by the control unit 200 via the accessory I/F unit 204. In response to the control unit 200 receiving the above-described information, the CPU 201 instructs the printer unit 209 to stop printing. The image forming apparatus 100 stops the printing operation by instructing the printer unit 209 to stop printing. Further, the inspection unit 110 causes the CPU 211 to transmit information to the finisher 120 via the accessory I/F unit 215. The information to be transmitted to the finisher 120 is information indicating whether the printed material has a defect. The finisher 120 discharges the printed material having no defect to a normal sheet discharge tray, and discharges the printed material having a defect to a tray different from the normal sheet discharge tray, based on the received information.

Next, inspection method selection for an inspection job according to the present embodiment will be described with reference to FIG. 3. FIG. 3 illustrates an example of a job property screen displayed on the UI unit 235 of the client PC 130.

An inspection method selection screen 300 is used to receive print job setting from the user in the client PC 130. The print job generated by the client PC 130 is transmitted to and managed by the information processing apparatus 140.

In a case where the user selects inspection “ON” in an inspection mode setting section 302, property setting is then performed. The print job in which inspection “ON” has been set is referred to as an “inspection job”. In a case where the user selects inspection “OFF”, the print job is handled as a normal print job, which is not to be inspected. The user selects a region to be inspected and an inspection level in an inspection setting section 303. In a case where “Default” is selected, the inspection apparatus 150 inspects an entire area of the image at a standard level. In a case where any of “Preset1” to “Preset10” is selected, the inspection apparatus 150 performs inspection based on a previously designated region and a previously designated level. In a case where “new registration” is selected, the user newly creates inspection setting, and the inspection apparatus 150 performs inspection based on the setting.

The user registers the reference image and/or selects a combination of print operation of the regular print job in an inspection operation setting section 304. In a case where “only registration” is selected, the inspection apparatus 150 performs only registration of the reference image and inspection setting thereof. In a case where “only printing” is selected, printing by the image forming apparatus 100 and inspection by the inspection apparatus 150 are performed using the previously registered reference image. In a case where “registration and printing” is selected, the operation in the case where “only registration” is selected and the operation in the case where “only printing” is selected are successively performed. Generation of the reference image and storage processing are described below. Finally, when a print button 305 is pressed, operation of printing and/or inspection is performed based on the setting input in the setting sections 302 to 304. When a close button 301 is pressed, the screen is closed without saving the setting of the screen.

Next, processing of job execution which is performed by the information processing apparatus 140 is described with reference to a flowchart in FIG. 4. The flowchart is realized by the CPU 241 loading program codes stored in the ROM 243 to the RAM 242 and reading out and executing the program codes loaded to the RAM 242.

In step S401, the CPU 241 determines whether a setting value (operation) set in the inspection operation setting section 304 illustrated in FIG. 3 is “only printing”. If “only printing” is set (YES in step S401), the processing proceeds to step S405. If the set operation is other than “only printing” (NO in step S401), the processing proceeds to step S402.

In step S402, the CPU 241 transmits a reference image registration job to the inspection apparatus 150. At this time, the RIP image, various types of print setting information, and the like are transmitted.

In step S403, the CPU 241 determines whether a registration completion notification has been received from the inspection apparatus 150. If the registration completion notification has been received (YES in step S403), the processing proceeds to step S404. If the registration completion notification has not been received (NO in step S403), the CPU 241 waits for the registration completion notification.

In step S404, the CPU 241 determines whether the setting value set in the inspection operation setting section 304 illustrated in FIG. 3 is “registration and printing”. If the setting value is “registration and printing” (YES in step S404), the processing proceeds to step S405. If the setting value is “only registration” (NO in step S404), the processing ends.

In step S405, the CPU 241 transmits a regular print job for inspection. At this time, the CPU 241 transmits the RIP image, various types of print setting information, and the like to the image forming apparatus 100, and the processing ends.

Next, processing of a registration work which is performed by the inspection apparatus 150 before start of inspection will be described with reference to the flowchart in FIG. 5. The flowchart is realized by the CPU 251 loading program codes stored in the ROM 253 to the RAM 252 and reading out and executing the program codes loaded to the RAM 252.

In the RIP inspection, the RIP image generated by the information processing apparatus 140 is transmitted to the inspection apparatus 150.

In step S501, the CPU 251 receives a start notification of the reference image registration job from the information processing apparatus 140.

In step S502, the CPU 251 receives the RIP image and the print setting information from the information processing apparatus 140. In this example, a five-page RIP image illustrated in FIG. 6A is received. In this example, an identification (ID) enabling determination of a page order is assigned to each image file name. In the present embodiment, for example, “*” portion in the file name “RefImage_*.tif” is identified as a page ID. The page ID is represented by, for example, a number or a character string. A method of imparting the page ID is not limited thereto, and information such as an ID list may be separately received from the information processing apparatus 140. The print setting information is setting information for single-sided printing, double-sided printing, or the like. In the present embodiment, setting of single-sided/double-sided printing will be described; however, for example, setting information for face-up/face-down discharging or forward order/reverse order printing may be received. In this example, the print setting information is acquired from the information processing apparatus 140. Alternatively, print setting may be performed from the UI unit 257 of the inspection apparatus 150 to acquire the setting value.

In step S503, the CPU 251 stores the image received in step S502 in a storage device, such as the RAM 252. The CPU 251 generates a sheet information list and stores the sheet information list in the RAM 252. FIG. 6B illustrates the sheet information list in a case where image data for five pages in FIG. 6A is registered as a reference image with double-sided setting. In a case where image data for an odd number of pages is registered as the reference image with double-sided setting as in FIG. 6B, a final page is a blank page having no corresponding reference image. In the present embodiment, the sheet information list is generated by the inspection apparatus 150 but may be generated by the information processing apparatus 140 and may be transmitted to the inspection apparatus 150. The sheet information list is a list including elements indicating correspondence of the page IDs to a print sheet and a print side thereof. An element 601 indicates a front side of a first sheet. A first page is printed on the front side of the first sheet. In this case, the page ID corresponding to the element is one. An element 602 is indicates a back side of the first sheet. Since the job is set to double-sided printing, a second page is printed on this side. Thus, the page ID corresponding to the element 602 is two.

A similar configuration is applied to elements 603 to 605. An element 606 indicates a back side of a third sheet. Since the print job includes five pages, the print data for the back side of the third sheet is absent, and the image data is not transmitted from the information processing apparatus 140. Thus, the inspection apparatus 150 stores a page ID corresponding to the element 606 as “blank” in the sheet information list. The page ID “blank” is illustrative, and the page ID is not limited thereto as long as the page ID indicates the blank page. In a case where a notification is issued from the information processing apparatus 140, any notification methods may be used with which a notification to the inspection apparatus 150 that the print data is absent and the image data is not transmitted from the information processing apparatus 140 is enabled.

In step S504, the CPU 251 determines whether all of the pages have been completely received. If all of the images have been completely received (YES in step S504), the processing proceeds to step S505. If a subsequent page is present (NO in step S504), the processing returns to step S502, and an image of the next page is received.

In step S505, the CPU 251 refers to the sheet information list stored in step S503 and determines whether a page having the page ID “blank” is present. If a page having the page ID “blank” is present (YES in step S505), the processing proceeds to step S506. If a page having the page ID “blank” is absent (NO in step S505), the processing proceeds to step S507. In step S506, the CPU 251 generates a blank reference image data corresponding to the page having the page ID “blank” and stores the blank reference image data in the RAM 252. Generating the reference image data for the page for which the print data is absent and the RIP image is not to be generated makes it possible to perform inspection on the blank page (blank surface) for which the reference image is not to be generated. In this example, the reference image corresponding to the blank page is generated; however, the configuration is not limited thereto. For example, the reference image data previously registered may be cited and stored in the RAM 252. The reference image corresponding to the page ID “blank” may not be stored in the RAM 252, and the reference data to be used for the subsequent inspection may be designated in step S506.

In step S507, the CPU 251 transmits the registration completion notification to the information processing apparatus 140.