S&F Ref: 868907 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name and Address Canon Kabushiki Kaisha, of 30-2, Shimomaruko 3 of Applicant: chome, Ohta-ku, Tokyo, 146, Japan Actual Inventor(s): Stuart William Perry Brendon Yenson Francois Degros Address for Service: Spruson & Ferguson St Martins Tower Level 35 31 Market Street Sydney NSW 2000 (CCN 3710000177) Invention Title: Detecting and marking incidental test patches in a printed document for the purpose of print quality analysis The following statement is a full description of this invention, including the best method of performing it known to me/us: 5845c(1 908103_1) -1 DETECTING AND MARKING INCIDENTAL TEST PATCHES IN A PRINTED DOCUMENT FOR THE PURPOSE OF PRINT QUALITY ANALYSIS TECHNICAL FIELD OF INVENTION The current invention relates to image processing, and in particular an automated method for assessing the quality of an image from an imaging system. BACKGROUND Many methods for analysing quality factors of an image forming device, such as a printer, are known in the art. Typical arrangements use a printer configured to produce a specialised test image, and an image capture device, such as a scanner or camera, to capture the image. By performing some sort of analysis of the captured image, this configuration can be used to measure image quality of the image forming device, the image capture device, or some combination of the two. Most modem imaging systems are digital, so the captured image is often analysed using automated methods on a computer. There are a wide variety of imaging devices available, and the types of quality features which can be measured are also diverse. For example, cameras have quality factors such as barrel distortion, chromatic aberration, and defocus, and printers have factors such as 5 geometric distortion and dot gain. There are also factors common to the imaging path of many devices, such as colour gamut or graininess. However, the large number of quality factors which need measurement causes a problem. It is not feasible to fit all factors within the one test image, and some factors cannot be measured without affecting other factors. The result is that multiple different images are often required to measure multiple aspects of an imaging ZO system. The simplest solution to this problem is to reduce the number of tested factors, so that only a single test image is required. However, this is clearly not an ideal solution as it limits the scope of what the system can achieve. Another simple solution is that the system can create 868907 / 1435872_1 260908 -2 and capture test images in a specific known (or user-assisted) order, and thus know how to analyse each captured image. There are other well known methods to monitor the print quality of a printer on the fly, using optical sensors such as scanners or densitometers embedded in the printer itself. Those 5 methods do not require the printing of special test images. However, the range of quality factors those methods can assess is limited. SUMMARY It is an object of the present invention to substantially overcome, or at least ameliorate, one or more disadvantages of existing arrangements. ) According to a first aspect of the present disclosure there is provided a method of adapting a user-selected document for use in quality analysis of an imaging system, comprising the steps of: analysing one or more attributes of the document to select an area of the document suitable for use in determining a quality factor of the imaging system; 5 generating description data relating to the selected area; and producing a printed copy of the document, wherein said document includes a machine readable mark encoding the description data. According to another aspect of the present disclosure, there is provided an apparatus for implementing any one of the aforementioned methods. 20 According to another aspect of the present disclosure there is provided a computer program product including a computer readable medium having recorded thereon a computer program for implementing any one of the aforementioned methods. Other aspects of the invention are also disclosed. 868907/1435872_1 260908 -3 BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described with reference to the following drawings, in which: Fig. 1 is a schematic flowchart diagram of a data processing method according to an i embodiment of the invention; Fig. 2 is a schematic example of a printed document; Fig. 3 is a schematic example of the document of Fig. 2 with an added machine readable mark; Fig. 4 is a schematic flowchart diagram illustrating how the scanned document is ) analysed; Fig. 5 is a table with examples of test patch types and analyses that can be performed on them; and Fig. 6 is an example configuration of an automated image quality analysis system in accordance with an embodiment of the invention. 5 DETAILED DESCRIPTION INCLUDING BEST MODE It is to be noted that the discussions contained in the "Background" section and that above relating to prior art arrangements relate to discussions of devices which form public knowledge through their use. Such discussions should not be interpreted as a representation by the present inventor(s) or the patent applicant that such documents or devices in any way !0 form part of the common general knowledge in the art. Documents to be printed are received by a printer encoded in a language called a page description language (PDL), i.e. a language that describes the appearance of pages to print in a higher level than an actual output bitmap. Examples of known PDLs include Portable Document Format (PDF), PostScript, Printer Command Language (PCL) and Scalable Vector !5 Graphics (SVG). 868907 / 1435872_1 260908 -4 The printer interprets the page description data provided via the PDL, creates a bitmap image representing the dots that are to be printed, and prints these dots on a substrate such as paper, resulting in a tangible printed document. The process of interpreting the page description data and creating the bitmap image to print is referred to as the RIP process. 5 In a broad aspect, a printer in accordance with the current disclosure analyses the PDL representation of a user-selected document, ie a document which the user has printed, in order to select one or more regions of interest, in order to adapt the document for the purpose of print quality testing. These regions of interest are referred to herein as incidental test patches. The printer also generates and prints a description of these incidental test patches on the ) document using a machine readable mark. These incidental patches can be used by the printer or some other quality analysis system to test the print quality of the printed document. For example, if upon reviewing a document, a user notices that a printed document has not printed correctly, this process allows the print quality to be tested. The results of this testing process may determine if any settings adjustments or recalibrations of the printer are required. Also, 5 by encoding the description of the incidental patches on the document itself, the testing process can be carried out at any time after the document is printed. Fig. 6 illustrates a simple arrangement of a system in accordance with the present disclosure. A computer 600 causes a printer 610 to produce one or more user selected documents 620. Some of the documents 620 contain one or more areas suitable for use as 20 incidental test patches 640, which can be used to measure quality features of the printer 610. Data related to the incidental test patches are encoded into a machine readable mark 630 (such as a barcode) which may be located on the printed documents 620. These documents are then digitally captured by a scanner 660 which is connected to a second computer 650. The first computer 600 and the second computer 650 can be the same machine, but do not have to be. 25 Also, it will be appreciated that one or both of the computers 600, 650 may form a part of the 868907/1435872_1 260908 -5 printer 610 and/or the scanner 660. The computer 650 analyses the digital images which are produced as a result of the scanning process, decodes the machine readable mark 630 in order to locate the incidental test patches 640, determines what quality analysis can be conducted using the incidental test patches 640, and performs this quality analysis. 5 Fig. I illustrates the global steps of the disclosed approach. Execution begins in step A10. In step A20, the printing engine receives the description of a document to be printed expressed in a PDL. In step A30, attributes of the document as defined in PDL are analysed by the printing engine in order to determine some incidental test patches for the purpose of print quality analysis. Some non-limiting examples of incidental test patches include text, text with D fine prints, uniform regions, regions with specific colour gamut, and regions with specific pattern like stripes or dots. The task of selecting incidental test patches can occur as part of the RIP process. Incidental test patches can be selected for their interesting properties, such as colour or filling (eg see Fig. 5). Also, incidental test patches should be visible on the printed material, and care should be taken not to select any region which is occluded by another 5 graphical object on the page. In step A40, a description of the selected incidental test patches is prepared. Depending on the nature of a test patch, the data included in the description of this test patch can be (but is not limited to) its location, its shape, its colour, and/or its filling. For example, an incidental test patch can be a rectangular area filled with a uniform colour. Its shape and location are 20 expressed in the document's coordinate system. Its shape is a rectangle with a width of 150 and a height of 100. The location of its lop left corner is (1500, 4000). Its filling is a uniform gray colour expressed in the CMYK colour space as (0, 0, 0, 0.5). In step A50, the document is printed, incorporating a machine readable mark which includes the description of test patches. Some non-limiting examples of machine readable 25 marks include 2D barcodes and modulated halftoning patterns. For example, 2D barcodes can 868907/14358721 260908 -6 be two-dimensional matrix barcodes consisting of black and white square modules arranged in either a square or rectangular pattern. The information to be encoded can be text or raw data. The length of the encoded data depends on the matrix dimension used. Error correction codes can be added to increase symbol strength, so that even if the barcode is partially damaged, it 5 can still be read. Depending on the nature of the machine readable mark, the position and/or orientation (expressed in the original document coordinate system) of the machine readable mark may be encoded in the machine readable mark itself. This information may be used during the analysis process to determine, for example, the orientation of a page which is scanned upside ) down or at an angle. In step A60, the printed document is scanned, resulting in an acquired image. In step A70, the machine readable mark is located in the acquired image and its content is extracted. Depending on the nature of the machine readable mark, one or more suitable localisation techniques can be used. For example, the machine readable mark can be located in the 5 acquired image based on its spatial or frequencial properties. The machine readable mark can also contain extra localisation marks or patterns, which can be located using a range of techniques such as cross-correlation. In step A80, the incidental test patches description extracted from the machine readable mark are used to determine the image quality analysis to be performed and the relevant area in 20 which the incidental test patch or patches are located. Once this is determined, the image quality analysis is performed on the scanned image. The results of this quality analysis provide quality factors of the printer used to print the document, which can then be used, for example, to configure or recalibrate the printer. Fig. 2 illustrates an example of a document as described in PDL. 868907 / 1435872_1 260908 -7 Fig. 3 illustrates an example of the hard copy of the same document, where some areas have been selected as incidental test patches (a zone with text B10, a uniform black rectangle B20, a circle with a black outline and no filling B30) and where a machine readable mark B40 has been added. Fig. 4 illustrates in greater detail the step A80 in Fig. 1, showing how the printed document is analysed. The steps A60 and A70 from Fig. I are reproduced in Fig. 4 for convenience. In step A60, the printed document is scanned. In step A70, the machine readable mark is located in the scanned image and its content is decoded. Machine readable marks are known in the art and methods for reading them from images are readily available. ) The localisation of the machine readable mark as found in the scanned image is expressed in the scanned image coordinate system. If the position of this machine readable mark in the original document coordinate system has been encoded in the machine readable mark itself, those two positions can be compared and used to determine the transformation between the original document and the scanned image. This transformation can be expressed as the 5 composition of a rotation, a scaling and a translation. In step D30, the test patches are located in the scanned image. The positions of the test patches, originally expressed in the original document coordinate system, are converted to the scanned image coordinate system using the transform deduced from the position of the machine readable mark. !0 In step D40, the analyses to be performed on each test patches are determined. This can be achieved by applying the description of the incidental test patches as determined and described in the machine readable mark to a repository of analysis techniques. The properties of each incidental test patch are used to determine which analysis techniques can be applied to each test patch. Then in a step D50 the suitable analysis techniques are applied to the image of 25 each test patch as extracted from the scanned image at the position determined in step D30. 868907/1435872_1 260908 -8 Fig. 5 gives some examples of suitable analysis techniques depending on the properties of the test patch. For example, the "granularity" analysis can be performed on test patches with a uniform filling and a sufficient surface area. In one arrangement, suitable analysis techniques can be determined when the test patches 5 are initially selected, and this information can also be encoded in the machine readable mark which is located on the printed page. In this way, any quality analysis carried out after the document has been printed does not require the quality analysis system to first determine which quality analysis techniques are appropriate for each incidental test patch. After the analysis has been performed, results of the analysis can be used to diagnose and ) qualify printing problems, and take any corrective actions which are required to rectify the problems. In this way, once the printed document is scanned for analysis, the original page description data is not required as the data facilitating the analysis process is contained in the machine readable mark on the printed document. Accordingly, a user is able to analyse the print quality 5 of a printed document accurately, even long after the document has been printed. Industrial Applicability The arrangements described are applicable to the computer and data processing industries. The foregoing describes only some embodiments of the present invention, and .0 modifications and/or changes can be made thereto without departing from the scope and spirit of the invention, the embodiments being illustrative and not restrictive. In the context of this specification, the word "comprising" means "including principally but not necessarily solely" or "having" or "including", and not "consisting only of'. Variations of the word "comprising", such as "comprise" and "comprises" have correspondingly varied 25 meanings. 868907/1435872_1 260908