FIG. 4 is an enlarged view of a portion of one of the test void pantographs of the test sheet of FIG. 2, where, in this example representation, the test void pantograph is generated with different dot sizes at the same black pixel density;
FIG. 5 is an enlarged view of a portion of one of the test void pantographs of the test sheet of FIG. 2, where, in this example representation, the test void pantograph is generated with different dot sizes and different black pixel densities; and
FIG. 6 is an enlarged view schematic representation of a portion of one of the test void pantographs of the test sheet of FIG. 2, where, in this example representation, the void pantograph is also generated with different dot sizes and different black pixel densities.
The embodiments disclosed herein utilize a test sheet of test void pantographs to generate one or more workflows for the printed material incorporating one or more of such void pantographs. The workflow(s) are not necessarily known a priori, but instead is/are a function of how the one or more void pantographs appear after printing and scanning.
As shown at reference numeral 100, the method includes generating a test sheet including multiple void pantographs. A non-limiting example of such a test sheet 10 is shown in FIG. 2. The test sheet 10 includes multiple void pantographs 12, each of which is generated from an image. It is to be understood that the void pantographs 12 on the test sheet 10 are test pantographs TP which are utilized to i) identify one or more pantographs 12 for subsequent deployment, and ii) generate a workflow for, or associated with the identified one or more pantographs 12.
The step of generating one void pantograph 12 is schematically depicted in FIGS. 3A through 3C. The void pantograph 12 is generated from an image 18, a schematic non-limiting example of which is shown in FIG. 3A. The image 18 may be any digitized image, including an image captured with a digital camera, camcorder, or scanner. The image 18 may also be produced by imaging software, graphics software, or the like. The image 18 may be any desirable image, and in some instances, may incorporate text, shapes, glyphs, embedded information to initiate, instantiate, continue, complete, etc. workflow(s), security applications, or other information that can be read and interpreted.
The image 18 is filtered using one or more filters. Non-limiting examples of such filters include an edge filter (e.g., Sobel, Canny, Laplace, neighborhood variance, gradient, etc.), a color filter, a hue filter, a chroma filter, a saturation filter, a brightness filter, an intensity filter, a luminance filter, a texture filter, a local entropy filter, a graininess filter, a specific shape filter, a threshold (Otsu, etc.) filter, a sharpness filter, a convolution filter, or other imaging filters. It is to be understood that one of the filters may be selected to filter the image 18, or multiple filters may be selected to filter the image 18. The filter(s) designate one or more areas for a pantograph foreground 14 (see FIG. 3C) and a pantograph background 16 (see FIG. 3C) based upon the particular attribute associated with the filter. For example, if an edge filter is selected to filter the image 18, the filtering process will identify edge pixels and non-edge pixels. The filtered pixels are then assigned to the pantograph foreground 14 or background 16, depending, at least in part, on which pixels are suitable for forming the respective regions of the pantograph 12. Such foreground and background pixels may be selected automatically or by printing samples of both and selecting based on the printed samples. In an embodiment, the higher information areas (e.g., higher edge content or image entropy or image high frequency content) are separated from the lower information areas to make a good void pantograph image. In the example involving the edge filter, the edge pixels may be assigned to the pantograph foreground 14, and the non-edge pixels may be assigned to the pantograph background 16.
In either of the previously described instances, maintaining static characteristics for one of the pantograph foreground or background 14, 16 enables the other of the pantograph background 16 or foreground 14 characteristics to be readily tested. As briefly mentioned above, the test pantographs TP are used to experiment with different characteristics in order to determine the best characteristics for deployment of the actual void pantograph 12.
As one example, when a 600 dots per inch (dpi) printer is to be used to print the test pantographs 12, TP 22 pixel dots (e.g., making up the foreground 14) and 11 pixel dots (e.g., making up the background 16) may be selected for the dot sizes. The percentage of black ink coverage may be varied by changing the density of dot placement. In order to select the desirable static background 16, multiple densities are tested prior to varying the foreground 14 characteristics. For example, the background 16 ink coverage percentage is tested at different values in the range of 5% coverage to 50% coverage of the total background 16 area. Such characteristics may be tested using a test sheet 10 similar to that described above. It is to be understood that any other variances may be used in subsequent (i.e., staggered, refined, or more limited range) test sheets 10 after a broader-range test sheet 10 is used to hone in on smaller, desirable range(s). In one non-limiting example, the 10% coverage for the pantograph background 16 is a suitable concentration. Such coverage increases brightness (i.e., the perceptual blackness diminishes), but the dots do not completely disappear when copied (printed and scanned), thereby affording a drop-out background suitable for testing the foreground 14 patterns. It is believed that other backgrounds 16 may be suitable as well, depending, at least in part, on the desirable characteristics for the deployed void pantograph 12 and the workflow associated therewith.
When generating the test pantographs TP to find the optimum void pantograph 12 characteristic(s) (e.g., densities), any background 16 characteristic may be held constant while one or more foreground 14 characteristics are varied, or vice versa. As one non-limiting example, the background 16 black pixel concentration (e.g., 10% black pixels) may be held constant while the foreground 14 concentration is varied from, for example, 4% to 25% in 1% or less increments (i.e., 40% to 250% as much as the 10% black pixels in the background).
The examples shown in FIGS. 2 through 6 illustrate test pantographs 12, TP in which the foreground 14 specifications do not overlap. It is to be understood, however, that two or more foreground 14 patterns may overlap. As a non-limiting example, a 5% black pixel coverage concentration foreground 14 may be distributed in multiple ranges of two pantographs 12 (or over most of the printed region), and as such, a 10% black pixel coverage concentration will be distributed in portions where the two foregrounds 14 overlap. In this example, the background 16 black pixel coverage concentrations may be 0%, 5% or 10%, depending upon the foreground 14 black pixel coverage concentration. In this example, for the entire printed region, the total foreground 14 black pixel coverage concentration at a particular portion plus the background 16 black pixel coverage concentration at that particular portion equals 10%. In some instances, this helps obscure the void pantograph TP, 12 until copied, i.e., this overlap produces the most desirable pantograph foreground 14, which is covert after printing and overt after scanning. The effectiveness of this overlap approach is variable, depending, at least in part, on the printer, scanner, and substrate (e.g., paper) used.
Once generated, the test sheet 10 is printed, as shown at reference numeral 102 of FIG. 1. From the printed test sheet 10, one or more of the test void pantographs 12, TP are identified as having a covert or semi-covert pantograph foreground 14 and background 16 (as shown at reference numeral 104 of FIG. 1). Generally, any pairing in which the foreground 14 is substantially visibly indistinguishable from the background 16 may be identified as a potentially suitable combination for subsequent deployment. The similarities between the foregrounds 14 and backgrounds 16 of the printed test pantographs 12, TP are evaluated or assessed manually (by a human observer) or are scored by an automated (e.g., machine vision) process.
The test sheet 10 is then scanned, as shown at reference numeral 106 of FIG. 1. From the scanned test sheet 10, one or more of the test void pantographs 12, TP are identified as having an overt pantograph foreground 14 (as shown at reference numeral 108 of FIG. 1). Generally, any foreground 14 that is visibly distinguishable from the background 16 may be identified as a potentially suitable candidate for subsequent deployment. The differences between the foregrounds 14 and backgrounds 16 of the printed and scanned test pantographs 12, TP are evaluated or assessed manually (by a human observer) or are scored by an automated (e.g., machine vision) process.
The test void pantographs 12, TP identified after printing are compared with the test void pantographs 12, TP identified after scanning. Any test void pantograph 12, TP identified as having both i) the covert or semi-covert pantograph foreground 14 and background 16 after printing, and ii) the overt pantograph foreground 14 after scanning is suitable for being deployed as the void pantograph 12 in a printed region on an object. It is to be understood that no, one, or multiple test pantograph(s) 12, TP may be identified at this point. Often, the test sheets 10 will include some effective void pantographs 12, some that have foregrounds 14 that are not visible/distinguishable after printing or scanning and/or some that have foregrounds 14 that are visible/distinguishabl