The invention relates generally to the field of image processing systems, and in particular to image processing systems that use image processing scripts to process one or more images in batch and interactive modes and where a specified level of image quality is desired for processed images.
Governments of many countries are digitizing historical documents and providing the digital image documents on the Internet, as well as archiving the digitized documents for future use. Paper-based medical records are also being digitized to provide electronic access to medical professionals for more efficient, timely, and accurate diagnoses. Similar digitization efforts are ongoing in commercial and government sectors to provide digital representations of legal and financial documents.
Each of these applications uses digital scanning to convert a physical medium to a digitized electronic representation. In producing the digitized electronic representation, image processing is applied routinely to the original scanned image data. Such image processing typically performs enhancement tasks including, for example, sharpening, rotation, brightness and contrast adjustment, and cropping. Increasingly, image processing also includes algorithms that interpret the data automatically, such as optical character recognition (OCR), barcode recognition, face recognition, or text layout analysis, to provide meaningful information to various search engines.
The image processing algorithms that are applied to scanned data are typically chosen by the operator performing the scanning, and the algorithm parameters are chosen to make the image “look good” from the operator's point of view. However, choosing image processing algorithms based on subjective quality using a single display at a single resolution may not anticipate other applications with different display characteristics or resolution needs. Moreover, choosing image processing to produce images that “look good” may not lead to optimal results in automatic data interpretation, such as in OCR, because important information that is used by OCR algorithms may be lost during image processing.
The paper documents that are scanned are often old and brittle and may be deteriorating even further over time. Scanning such documents properly the first time is extremely important because repeated handling can lead to further deterioration. In addition, mistakes during scanning and image processing can be very costly in light of the huge volumes of documents that are being scanned. It is easy to generate a lot of bad data fairly quickly, and recovering from such mistakes can be expensive and time consuming.
In an effort to help achieve higher quality and more consistent scanned data, various industry and government groups are publishing recommendations for scanned image quality. One example of a published recommendation is: Steven Puglia, Jeffery Reed, and Erin Rhoads, “Technical Guidelines for Digitizing Archival Materials for Electronic Access: Creation of Production Master Files—Raster Images,” U.S. National Archives and Records Administration (NARA), June 2004. This document provides recommendations for image quality metrics that meet the needs of the archiving and cultural heritage communities. It includes recommended techniques for measuring basic quality attributes such as sharpness, tone scale, noise, and color, and also provides preferred values for at least some of the measured quality variables.
In general, the quality measurements specified in such publications are made using test targets. Test targets are special physical media that include content having various known or premeasured properties. Test targets serve as references so that the image quality attributes of scanned data can be measured accurately and precisely. There are various companies that offer software products that allow one to measure test targets for one or more of the quality metrics needed to follow these published image quality recommendations.
There are several limitations with currently available test targets and software that measure quality metrics of the scanned image data containing test targets. One limitation is that the software products typically require manual identification of one or more image regions containing test target content so that the desired quality metric or metrics can be measured. In some products, the calculation of each quality metric requires a separate manual intervention step, which is very labor intensive. Another limitation is that once all of the quality metrics have been calculated, it is then necessary to manually compare each metric against the desired value. Moreover, both the quality analysis and quality comparison steps must be repeated if the image processing steps are changed in any way, such as the addition/deletion of a step, changing the order of the steps, or changes in the processing parameters used in a step.
This overall quality analysis process quickly becomes burdensome in actual production workflows where there may be a need to evaluate the image quality for different combinations of image processing steps and the associated processing parameters. Moreover, it may also be necessary to evaluate the quality metrics against a plurality of image quality profiles if the scanned image data is intended to be used in different applications. Such evaluations can be very time consuming and laborious.
Therefore, there is a need to overcome these limitations and provide faster and more convenient methods and systems for the processing of images to meet a desired level of image quality.
Broadly speaking, the invention relates to an image quality indicator, responsive to image processing steps, that provides feedback regarding the image quality associated with a change in the image processing steps or a change in a parameter within an image processing step. The quality feedback is provided in such a way that a quick determination can be made as to whether or not the image processing is sufficient to meet a predefined quality need.
In providing feedback as to whether or not the image processing is sufficient to meet a predefined quality need, the present invention includes one or more image quality profiles that represent the range of acceptable quality values for one or more image quality metrics; an image processing module to process image data using one or more image processing steps in accordance with a processing script; an image quality processor that performs an automated analysis of processed image data to produce one or more image quality metrics; and an image quality indicator responsive to the image processing indicating whether or not the processed image data meets the acceptable values of the quality metrics.
The invention can be implemented in numerous ways, including as a method, system, device, apparatus, graphical user interface, or computer readable medium.
Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
It is an advantage of the method of the present invention that it allows a user to evaluate various combinations of image processing steps (and associated processing parameters) and image quality profiles in a fast and efficient manner through use of an image quality indicator.
These and other aspects, objects, features, and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings.
In the disclosure that follows, elements not specifically shown or described may take various forms well known to those skilled in the art.
Embodiments of the present invention execute on one or more computers or dedicated image processors that execute stored instructions for processing image data. Various arrangements of computer and related processor hardware are contemplated, including networked processors, for example. Transfer of data between processors and to and from data storage and memory devices can be effected using various types of wired or wireless network transmission or other forms of data interface, such as using removable magnetic or optical media, for example.
Embodiments of the present invention are executed on a computer or other type of control logic processor, such as a networked computer or host, dedicated processor or microprocessor, or other logic control device that is capable of executing programmed instructions. It can be appreciated by those skilled in the image processing arts that embodiments of the present invention can execute on any of a number of control logic processor configurations and using any of a number of processors, including networked processors. With any type of computer or other control logic processor, computer-accessible memory storage is provided in some form. Longer term storage can be provided, for example, by optical and magnetic storage devices, such as hard drives and CD or DVD storage disks. Short-term memory storage is generally provided by electronic circuitry, using random-access memory (RAM) or other memory circuitry to provide temporary workspace during processing, data transfer, or display.
The invention is directed to forming a digital file from image data generated by digitization of an “original” from a physical medium or a physical scene. The physical media may, for example, include originals of any of various types of written, printed, or imaged records such as bank checks, X-ray film, photographic film, historical letters, scholarly papers, photographs, income tax forms, and book or periodical pages, for example. Physical scenes include any physical entity or entities, such as people, places, and objects, for example, that have been imaged onto an image capture device. Embodiments of the present invention encompass image data from any manner of digital image capture device. Some types of image capture devices pass physical media over one-dimensional (1-D) line sensors (such as a scanner) to construct a two-dimensional (2-D) image data representation. Other imaging devices use a 2-D sensor (such as a digital camera) to directly produce a 2-D image data representation of a physical media or scene. The image data may also include a sequence of digital images, such as those produced by a video camera, where each frame of the image sequence is treated as a separate image for the purpose of the present invention. Image data acquired by any of these means is referred to herein using the general term “scanned image data”.
A preferred embodiment of the present invention is directed toward high volume document scanning, which necessitates minimal user intervention while maintaining the highest possible image quality. It is in this environment wherein significant cost savings can be obtained by the practice of this invention. However, it is appreciated that the invention can be equally applied to low volume scanning as well.
Returning to
Image processing script 160 is a set of instructions that describe how to perform image processing and thereby generate processed image data. Image processing script 160 includes a set of one or more image processing steps and associated processing parameters for each step. An image processing script can be very complex, specifying a sequence or combination of processing operations such as optical character recognition (OCR), geometric distortion removal, image compression, nonlinear enhancement, object detection, sharpening, smoothing, gamma correction, despeckle, blur, grayscale conversion, white balance adjustment, bordering, cropping, and noise cleaning, for example. However, an image processing script can be as simple as specifying that a single sharpening or resize operation is to be performed.
Referring to
Automated target recognition 230 is employed on the processed image data, using prior art techniques that may include the detection of fiducials, such as the two example fiducials 215 shown on the target 210 in
Some earlier examples of automated detection of targets are found in U.S. Pat. No. 5,825,913, “System for finding the orientation of a wafer”; U.S. Pat. No. 5,673,334, “Method and apparatus for inspection of characteristics on non-rigid packages”; U.S. Pat. No. 5,640,200, “Golden template comparison using efficient image registration”; U.S. Pat. No. 5,548,326, “Efficient image registration”; and U.S. Pat. No. 5,500,906 “Locating curvilinear objects using feathered fiducials”.
The values corresponding to individual quality metrics 250 are then compared against acceptable quality values as provided in an image quality profile 270, described in more detail subsequently. This comparison process is done by a quality comparison 260. If all of the quality metrics fall within the range of acceptability defined in the quality profile, an image quality indicator 280 indicates “Pass” status. Otherwise, image quality indicator 280 indicates “Fail”. The “Pass/Fail” status indicator can include a variety of methods and devices, including text messages showing “Pass/Fail”, “OK/Not OK”, or “Good/Bad”, and color-coded symbols or lights (green or red), for example.
For each document page in document queue 110, the processed image data automatically undergoes target recognition, image quality analysis, and quality comparison. For convenience, the combination of target recognition 230, image quality analyzer 240, and quality comparison 260 is denoted as target and quality processor 290, as illustrated in
After target and quality processor 290 has analyzed the processed image data and compared the quality metrics 250 against the image quality profile 270, a user receives immediate quality feedback from quality indicator 280, such as on a display screen, for example. Moreover, when a processing script is changed in any way, including, for example, the addition/deletion of a step, the order of existing processing steps, and the parameters used in a step, the sequence of operations depicted in
In the preceding discussion, the image quality metrics are calculated only from image quality test target 210. In commonly assigned co-pending U.S. Patent Application No. 2010/0021001 entitled “Method for Making an Assured Image” to Honsinger et al., quality metrics are disclosed that do not depend on a test target and are calculated directly from the image content. The present invention can easily accommodate such “targetless” quality metrics and in a preferred embodiment of this invention, both target-based and targetless metrics are used. The co-pending Honsinger et al. '1001 application also provides a detailed description of different examples of image quality metrics and the targets that could be used to measure such metrics. In one embodiment, the description of the image quality target 210 is achieved by using XML (eXtensible Markup Language) notation. For example, in the preferred embodiment, the physical target dimensions are described in inches. Similarly, the fiducial centers are described in the units of inches and in a coordinate space defined within the physical dimensions of the physical target. Once the fiducials 215 are identified using the automatic target recognition described above, the region or coordinates of the processed scanned image data 180 occupied by the image quality target 210 can be calculated by a simple geometric transformation. By identifying the target area within the scanned image data 180, the area outside of the target can be used to calculate targetless metrics as defined in the co-pending Honsinger et al. '1001 application. Moreover, it is possible to calculate only targetless quality metrics for scanned image data that does not include a test target anywhere within the image.
It is worthwhile to note that when only target-based quality metrics are used, it is possible to apply image processing only to the detected target region and still compute the necessary quality metrics. The benefit of such an approach is that processing time can be reduced (because the target typically makes up only a fraction of the total image data), thus giving a user more rapid feedback on the image quality when a number of different image processing scripts are being evaluated. Once a desired level of quality has been achieved with a particular processing script, the entire body of scanned image data can be processed with that script to produce the processed image data.
Still referring to the processes shown in
Referring now to
In
An image processing script window 350 is provided as a place to see a list of the elements 360 that comprise the image processing script. The state of image processing script elements 360 is entirely equivalent to image processing script 160.
In
In one embodiment, image processing script 160 is represented as an XML (eXtensible Markup Language) file. An XML representation provides a convenient and easy way to port image processing scripts over different platforms and different applications.
Referring again to
To manage image quality profiles, an image quality profile editor can be used.
Each quality requirement can be represented as a set of lower and upper limits for the individual image quality metric. Combined sets of lower and upper limits that contain one or more quality requirements form an image quality profile. If a user scans image data for multiple purposes, for example, there may be a variety of different image quality profiles in use at a particular scanning site. In one embodiment, an image quality profile is represented as an XML file.
Referring once again to
A further reporting capability is shown in the example of
It should be noted that there is always a tradeoff in addressing image quality deficiencies with image processing functions. If a noise cleaning process is added to the image processing script elements 360 to address the excessive noise discussed above with reference to
Many scanner operators or users may not have the sophistication to independently make a change in the image processing script to address a deficiency in the image quality. For such users, it can be preferable to have a single image quality indicator reflecting whether or not a processed image meets all of the quality requirements defined by the image quality profile. As depicted in
In one embodiment, using the operator interface of
In an alternate integrated embodiment, scanner 130 can contain within itself computer 140, scanned image data 150, image processor 170, and processed image data 180. Image processing script 160 can be downloaded to scanner 130 via an Internet or other network connection, for example, or the script (or scripts) can be preloaded into scanner memory. Processed image data 180 can then be output from the integrated embodiment of scanner 130 to storage 190. This integrated embodiment can be realized using modern day scanning and computer technologies.
An example LCD screen, display 700, appearing on the scanner is depicted in
In response to a change in the sharpening strength, target and quality processor 290 is run on image quality test target 210 and sailboat image 720 in an identical fashion as in the previously described embodiment. If all of the measured quality metrics fall within the range of acceptability defined by the selected quality profile, a green LED light is displayed to provide image quality indicator 280. Otherwise, a red LED light is displayed as image quality indicator 280. If the quality is indicated as being unacceptable, a user could then take various actions, such as rescanning and/or changing the sharpening strength. Among its advantages, this alternative embodiment allows changes to scanning conditions to be discerned and rectified at the scanner itself, allowing for changes in the scanner acquisition parameters rather than relying on post scanning correction. In general, it is advantageous to acquire scans with the preferred set of parameters rather than relying on post scan processing.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
110 document queue
120 current document
130 scanner
140 computer
150 scanned image data
160 image processing script
170 image processor
180 processed image data
190 storage
210 image quality test target
215 example fiducials
220 example page from a 19th century Farmer's Almanac
230 target recognition
240 image quality analyzer
250 image quality metrics
260 quality comparison
270 image quality profile
280 image quality indicator
290 target and quality processor
330 image display window
340 image display navigation tools
350 image processing script window
360 image processing script elements
365 image processing script editor tools
370 image quality profile selection interface
380 set of image quality indicators
382 quality detail window
390 pass/fail image quality indicator
410 “SharpenOperation”
420 sharpening strength
510 image quality profile “input-output” tools
520 metric attribute tabs
530 minimum effective DPI (h)
540 maximum effective DPI (h)
610 “DpiValues”
620 minimum acceptable DPI
630 maximum acceptable DPI
700 display
710 sharpness strength trackbar
720 sailboat image
740 scanner apparatus
750 control logic processor
800 scanning system
Priority is claimed from U.S. Ser. No. 61/175168, provisionally filed on May 4, 2009, entitled “IMAGE QUALITY INDICATOR RESPONSIVE TO IMAGE PROCESSING”, in the names of Paul W. Jones et al., commonly assigned and incorporated herein by reference.
Number | Date | Country | |
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61175168 | May 2009 | US |