Method and apparatus for anisotropically modifying text attributes to comply with resolution limits

Abstract

A computer-implemented method for proofreading a selected portion of a graphic data input file for output to an output device by automatically adjusting at least one graphic feature in the input file to compensate for a predetermined resolution limit. The method comprises: identifying one or more portions of the selected portion of the input file having an initial coarseness less than the resolution limit; determining a set of optimal anisotropic offset parameters that will bring the one or more portions above the predetermined resolution limit with a minimum total offset value; applying an offset using the anisotropic offset parameters to modify the selected portion of the input file to give the one or more portions an adjusted coarseness greater than the initial coarseness; and creating an output file including the at least one graphic feature having the adjusted coarseness.

Description

Background Art

[0001] In printing, producing thin lines can be a challenge. Usually, there is a minimum thickness for the line to be printed in a stable and reliable manner. For gravure printing, a typical value is 50-100 microns (depending on the engraver and printer). If the lines of the digital image are thinner, there is a risk that they will not be imaged on the printing plate and / or will not be transferred to the substrate.

[0002] Text can have many thin lines, especially when the point size is small and / or the font uses thin strokes. If some of these lines are not printed reliably, the text can easily become difficult or impossible to read. Missing strokes can even change the meaning of the text. For example: "1-2 tablets per day" can become "12 tablets per day".

[0003] Some fonts also have very fine decorative features (such as serifs). When these smaller parts are not reproduced reliably, the text is still fully readable, thus providing some tolerance for the finest parts of a property that cannot be fully reproduced on the page in some cases.

[0004] The problem may occur in both Western and Asian fonts, particularly when there is a strong contrast in thickness between strokes in different directions. For example, the horizontal lines in the Chinese characters depicted in Figure 1 are much thinner than the vertical lines. Asian fonts such as Ming (Japan) and Song (China) are widely used in printing. In the case of Western text, the "serif" style of the font is also characterized by variable stroke thickness.

[0005] Furthermore, the minimum stable thickness of a line may also depend on the direction of the line. In the case of flexographic printing, for example, thin lines imaged parallel to the printing cylinder may suffer from different artifacts than lines along the printing direction.

[0006] There are many methods to avoid or reduce this problem. In most cases, the digital drawing is modified to make the problematic strokes thicker. In one method, the prepress operator uses manual tools to deal with these printing problems, but they can be time consuming and imperfect. One of the manual ways to solve this problem is for the operator to stack multiple copies of the same text on top of each other with a small vertical offset, such as depicted in the before and after figures in Figures 2A and 2B, respectively. While this method makes the horizontal strokes appear thicker without modifying the thickness of the vertical strokes, it causes a lot of work for the operator and may cause some artifacts at the ends of the strokes 200. In addition, the operator must perform careful measurements to prevent thickening the strokes more than necessary.

[0007] There are also some automated tools to solve this problem. TMThe tool detects the thinnest part from the text and creates a new stroke with the exact minimum line thickness above the thinnest part of the stroke. TM The tool is DeskPack distributed by Esko Software BVBA, the assignee of the present invention. TM A similar method is generally described in U.S. Patent No. 8,648,862, entitled "METHOD FOR AUTOMATICALLY MODIFYING A GRAPHICS FEATURE TO COMPLY WITH A RESOLUTION LIMIT," assigned to the assignee of the present invention and incorporated herein by reference. This method eliminates manual measurement work and avoids over-bolding. However, one disadvantage is that the added strokes may destroy the visual integrity of the font. Therefore, text with the added strokes may look unbalanced and may not resemble the original font.

[0008] HQH Pro software distributed by HELL Gravure System can also handle thin lines in text. In this solution, the digital image is first rasterized into a pixel image, then an algorithm is used to increase the line thickness before the image is sent to the intaglio printing device. This solution is not optimal for fonts that often have non-uniform vertical / horizontal strokes (such as Song / Ming) because everything is offset. Summary of the invention

[0009] One aspect of the invention includes a method for proofreading at least one selected portion of a graphic data input file for output to an output device. The method includes automatically adjusting at least one graphic feature (such as a text character or a portion thereof) in the input file to compensate for a predetermined resolution limit using a computer, the computer being programmed to perform such adjustment. The method includes automatically identifying one or more portions of the selected portion of the input file having an initial coarseness less than the predetermined resolution limit using the computer, and then automatically determining a set of optimal anisotropic offset parameters that, when applied, will cause at least a selected percentage of the one or more portions to be above the predetermined resolution limit with a minimum total offset value. The selected portion of the input file is automatically modified using the computer by applying an offset using the identified set of optimal anisotropic offset parameters so that the adjusted coarseness of at least the identified one or more portions is greater than the initial coarseness. The computer then creates an output file including the at least one graphic feature having the adjusted coarseness. The selected portion of the input file may include a plurality of strokes, wherein the one or more portions include strokes that are less than all of the plurality of strokes, and wherein the step of automatically modifying includes applying the offset to all of the plurality of strokes in the selected portion of the input file rather than applying the offset to only the one or more portions identified as having the initial thickness less than the predetermined resolution limit.

[0010] The step of automatically determining the set of optimal anisotropic offset parameters may include analyzing the results of a skeletonization operation, which may include the following steps: constructing a 2-dimensional histogram representing the stroke direction divided into 180 / n direction intervals of n degrees each and k weight intervals equally divided in a range between 0 and the predetermined resolution limit, wherein the value of each cell in the interval includes the total stroke length of the identified portion of the file having the stroke direction and the weight defined by the cell. Then, the analysis may include iteratively testing multiple offset conditions until the total stroke length represented by the sum of all cells in the histogram is less than or equal to a predetermined percentage of the total stroke length of all strokes in the identified portion. The offset may be applied by modifying or adding a vector map to the one or more portions. The at least one graphical feature may include a non-Latin text character, and the selected portion of the file may include one or more numeric characters representing text having a common size and a common font.

[0011] The method may further include: in a first instance, storing in the computer, in association with the graphical feature, information identifying the adjustment made to compensate for the predetermined resolution limit of the graphical feature; and in a second instance, using the stored information when the same graphical feature is encountered. The selected portion may include one or more digital characters representing a font set, in which case storing the information identifying the adjustment may include storing a modified font set. The information identifying the adjustment may be stored in a short-term computer memory storage device, and the first instance and the second instance may be encountered when processing a single input file or multiple input files associated with a single project. The information identifying the adjustment may also be stored in a long-term computer memory storage device, wherein the first instance and the second instance relate to a first input file and a second input file processed for use in conjunction with the output device.

[0012] The offset may be applied to a rasterized version of the text. The identification of the selected portion of the input file having the at least one graphical feature and / or the predetermined resolution limit may be received as user input. The predetermined resolution limit may be a user imposed limit or may be defined by an output device having a resolution limit lower than a resolution limit of the input file.

[0013] Another aspect of the present invention includes a system for proofreading at least a selected portion of a graphic data input file for output to an output device. The system is configured to automatically adjust at least one graphic feature to compensate for a predetermined resolution limit. The system includes a controller, the controller including a processor having a memory, the processor being programmed with instructions for performing the method steps described herein. The system may also include the output device, such as a printing press, a printing plate maker, or a cutter connected to the controller.

[0014] Yet another aspect of the present invention includes a non-transitory computer readable medium including program instructions for proofreading at least a selected portion of a graphic data input file for output to an output device, the instructions being programmed to automatically adjust at least one graphic feature in the input file to compensate for a predetermined resolution limit. The program instructions, when executed by a processor, cause the processor to perform the method steps described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 shows a set of exemplary Chinese text characters having different stroke lengths for horizontal versus vertical strokes.

[0016] FIG. 2A shows a set of exemplary Chinese text characters requiring line bolding.

[0017] FIG. 2B illustrates the group of Chinese text characters of FIG. 2A after applying an exemplary prior art bolding method.

[0018] FIG. 3A illustrates a prior art conventional offset method applied to a shape.

[0019] Figure 3B A visualization showing the conventional migration method applied in FIG. 3A .

[0020] FIG. 4A shows the anisotropic migration method applied to the same shape depicted in FIG. 3A .

[0021] Figure 4B A visualization showing the anisotropic migration method applied in FIG. 4A .

[0022] Figure 5A is a flow chart depicting an exemplary line thickening method according to the present invention.

[0023] Figure 5B A more detailed description Figure 5B Flowchart of an exemplary line thickening method.

[0024] FIG6 depicts the geometry of an ellipse and the equations associated therewith. DETAILED DESCRIPTION

[0025] One aspect of the present invention improves the readability of printed text by applying a path offset operation to a digital image. One benefit of the offset operation is that it can be applied equally to all characters of the text, and therefore the offset operation better maintains the balance and visual consistency of the font compared to other types of solutions. In addition, in a preferred embodiment, the offset operation is anisotropic, which means that the offset distance may be different in each direction. In particular, the use of anisotropic offsets has been found to be very effective for serif fonts and Ming fonts.

[0026] The parameters of the offset are automatically calculated to make the printed text readable but to make as few changes to the text as possible. Figure 5A The general flow of the exemplary method 500 is depicted in Figure 5B The general flow of the exemplary method 500 is described in more detail in . In general, after establishing and accepting the minimum line thickness 510, the user selects a portion of the vector image representing text (also referred to simply as "text") and accepts it for analysis. Then, optimal offset parameters are calculated based on the analysis of the shape of the text 530, and an offset operation is applied to the text 540 using the optimal offset parameters.

[0027] Offset Path

[0028] Path offset is a well-known operation and is widely used in computer graphics, for example, when a spline curve with a given stroke thickness must be rendered. The resulting path is a fixed distance from the original path. For example, as shown in Figure 3A, the outer boundary 310 of the shape 300 is offset from the inner boundary 320 by a fixed distance. The fixed distance can be represented as a certain distance as depicted in Figure 4A, which is 1 / 2 of the diameter D of the circle 400 centered on the inner boundary line. Therefore, each arrow (arrow 315 in Figure 3A) represents D / 2 as depicted in Figure 4A. Sharp angles are often treated differently based on user preferences, such as by using a "bevel connection" algorithm during the offset generation step to maintain the sharpness of the angle, which is common in the printing industry and well documented elsewhere, and is not discussed in detail in this article.

[0029] Figure 3B and 4B The anisotropic path offset depicted in is very similar to a regular offset, except that the distance of the new path from the original path depends on the direction, just as the different thicknesses of an ellipse depend on the direction in which it is measured. While a regular offset (e.g., a circle) has 1 parameter (the distance D), an anisotropic offset operation (e.g., an ellipse) has 3 parameters: the offset distance in the direction of the major diameter (D), the angle in the main direction (α), and the offset distance in the direction of the minor diameter perpendicular to D (d), where D>d. Therefore, a regular path offset can also be expressed using the equation for applying an anisotropic offset, where D=d. Offsetting in only one direction is a special case of anisotropic offset. Therefore, if Figure 3B As shown, providing an anisotropic offset can be represented as applying ellipses 410a-410d to the same inner boundary 320 of FIG. 3A, which produces an outer boundary 340 that is very different from the outer boundary 310 and results in different thicknesses for each stroke of the character depending on the stroke direction, as depicted by the different lengths of arrows 345, 347, and 349. As depicted in FIG. 6, the length of the tangent line T of the ellipse can be represented by Equation 1:

[0030] T=2*sqrt(D 2 sin 2 θ+d 2 cos 2 θ)(1)

[0031] Therefore, in the same way as for an ellipse, it is possible to describe how the thickness of an angled line changes as a result of an anisotropic shift with parameters D, d, α and β, where α = the angle at which the ellipse is applied relative to the horizontal and β = the angle of the line to be shifted relative to the horizontal.

[0032] New line thickness = old line thickness + 2*sqrt(D 2 sin2 (α-β)+d 2 cos 2 (α-β))(2)

[0033] Therefore, when the line is parallel to the direction of the main offset (ie, α = β), the thickness will increase by 2d (which is the minimum). When the line is perpendicular to the direction of the main offset (ie, α = (β ± 90), its thickness will increase by 2D (which is the maximum).

[0034] Stroke Thickness-Direction Histogram

[0035] In order to calculate the offset parameters by applying the anisotropic offset in step 520, the method includes first performing a skeletonization operation 532 on the text, which is well known in computational topology (and is also described and illustrated in U.S. Patent No. 8,648,862, which has been incorporated herein by reference). The result is an alternative representation of the text: a set of strokes of total length L, where the direction and thickness of each stroke can vary along the length of the stroke. Next, in step 534, a two-dimensional histogram of stroke thickness versus stroke direction is compiled. For example, in the exemplary embodiment described herein, the stroke direction can be divided into 36 5-degree direction intervals (or more generally, 180 / n n-degree direction intervals) that define the columns of the histogram. The stroke thickness is divided into 25 weight intervals (or more generally, k intervals) that equally divide the range between 0 and the minimum line thickness. These weight intervals define the rows of the histogram. The exemplary histogram is depicted as histogram 1 below, in which only the initial two rows and two columns and the last two rows and two columns are depicted with data. The value in a histogram cell represents the total length of all stroke parts that fall within the given direction interval and the given weight interval of that cell. All stroke parts thicker than the minimum line thickness are not included in the histogram.

[0036] Histogram 1

[0037]

[0038]

[0039] L0 is defined as the sum of the values ​​of the histogram cells (ie, the total length of the stroke parts thinner than the minimum line thickness). If L0 is less than 1% of L (where L = total stroke length), then no further shifting is considered necessary. Otherwise, the analysis continues.

[0040] Simulating anisotropic shift on histogram

[0041] For a given offset parameter (D, d, α), Equation 2 is used to evaluate each histogram cell, i.e., whether the stroke portion represented by the cell is still below the minimum line width. Function L(D, d, α) is defined as the sum of the values ​​of the cells in the histogram that are still below the minimum line width (according to Equation 2). An exemplary histogram 2 is depicted below, again showing only the data for the first two rows and two columns and the last two rows and two columns, together with rows showing the offset associated with each column calculated using the applied offset value (D, d, α).

[0042] Histogram 2

[0043] <![CDATA[ 0..5° ]]> <![CDATA[ 5..10° ]]> <![CDATA[ ... ]]> <![CDATA[ 170..175° ]]> <![CDATA[ 175..180° ]]> 48..50m 0.321mm 0 ... 0.142mm 0.372mm 46..48m 0 0.253mm ... 0.328mm 0.003mm 44..46m 0.182 0.123mm ... 0 0.014mm 2..4m 0 0.003mm ... 0 0.015mm 0..2m 0.021mm 0.001mm ... 0.021mm 0.007mm Offset: +4.1m +3.8m +3.9m +4.2m

[0044] Thus, for the offset with parameters (D, d, α) defined in this specific example, the results of Equation 2 are shown in the bottom row to indicate how much thicker the stroke will be for each angle. The offset values ​​along the intervals in the left column can be used to determine whether all the strokes represented in the cells will become thick enough (at or above the minimum threshold for line thickness), or whether some or all of them are still below the minimum line thickness. L(D, d, α) is the sum of the cells below the minimum line thickness, representing the total length of the strokes that are still below the minimum stroke thickness after the offset is applied. Different values ​​of (D, d, α) are iteratively tried in step 536 until an optimal set of parameters is found. For example, in one embodiment, the optimal parameter set is defined as the parameter set that solves Equation 3:

[0045] L(D,d,α)≤TV*L (3)

[0046] For multiple values ​​of D, d that satisfy this equation, the group with the minimum value of D+d is selected. This ensures that the vast majority of text strokes are above the minimum line thickness. Because the text may also contain decorative features (e.g., serifs) that are not critical to readability, a tolerance value TV of 1% (0.01) is applied in this exemplary embodiment, but the invention is not limited to a particular tolerance value, or the application of any tolerance value. The result is essentially a three-dimensional optimization problem. There are many different ways to solve this type of problem. In one embodiment, an exhaustive search using discrete values ​​of D, d, and α (equivalent to intervals of a histogram) can be run.

[0047] The foregoing describes only one possible way to find the optimal anisotropic offset parameters. Many methods are possible. For example, in a pixel-based approach, the following steps may be performed:

[0048] (a) Rasterize the text into a black and white pixel image (black text on a white background)

[0049] (b) Define a run as a horizontal or vertical row of continuous black pixels bounded by white pixels on either side. Optionally, more than 2 directions may be considered by repeating the above steps for a rotated version of the text.

[0050] (c) For each direction (horizontal and vertical), determine the minimum offset (θ) required to make 95% of the segments at least as long as the minimum line thickness. h and O v ).

[0051] (d) Using anisotropic offset parameters (O h ,O v ,0) or (O v ,O h ,90) to continue.

[0052] In yet another example, a brute force calculation may be performed by considering a set of combinations of offset parameters. For example:

[0053] (a) In X (eg, 5) steps, select D and d ranging from 0 to half the minimum line thickness, where α = a finite number of angles (eg, 0 or 90 degrees).

[0054] (b) Delete invalid and equivalent combinations. For example, X = 5 and α = 0 or 90, resulting in 25 combinations of offset parameters.

[0055] (c) Automatically try these combinations one by one (in ascending order of D+d) through the offset path.

[0056] (d) For each attempt, calculate the total length of the strokes below the minimum line thickness (e.g., based on skeleton analysis).

[0057] (e) Repeat (a)-(d) until a combination is found under which no more than 5% of the stroke lengths are below the minimum line thickness.

[0058] Once the best offset parameters have been chosen, the next step is to apply the offset to the text. There are many ways to modify the digital image to achieve this effect. For example:

[0059] (A) Replace the original text graph with a new closed path, as computed by the offset algorithm.

[0060] (B) Add a new closed path to represent the difference between the text and the offset text.

[0061] (C) Rasterize the text and apply an offset to the pixel image (e.g., using a convolution operation).

[0062] (D) Assign stroke attributes to the vector image. For uniform offsets, this is trivial, but vector file formats can also support anisotropic offsets. For example, in a PDF document, this can be performed by combining the strokes with multiple transformations.

[0063] (E) The offset parameters are attached to the graph as metadata and the convolution operation is performed during the raster image processing (RIP) stage.

[0064] (F) Applying the offset to the font used for the text. For example, all glyphs in the font (or a subset thereof) may be analyzed to determine optimal offset parameters (for a given point size and minimum line width) and variants of the font created using the offset glyphs.

[0065] It will be appreciated that the inverse problem may also be considered, where the spacing between two text features is less than the minimum resolution, resulting in (for example) two parallel lines that are so close together that they risk printing as a single line. When evaluating the path shift, a shape analysis may be performed on the inversion of the text to evaluate the damage that the (positive) shift may cause to the spacing between the text. Therefore, the method applied herein may be applied to the inversion of text features using the same principles. For example:

[0066] 1. Skeletonize text and the spacing between texts

[0067] 2. Build two stroke histograms: one for text and one for spacing

[0068] 3. Try different offset parameters and evaluate the impact on both histograms (text strokes will become wider, spacing strokes will become narrower)

[0069] 4. Define L(D, d, α) as the total length of text strokes below the minimum thickness, and define S(D, d, α) as the total length of spacer strokes below the minimum thickness (both after applying an offset with parameters (D, d, α)).

[0070] 5. Find the optimal value of (D, d, α) where L(D, d, α) + S(D, d, α) ≤ TV*L and D+d is minimal. If this is not possible, then find the optimal value of (D, d, α) where L(D, d, α) + S(D, d, α) is as small as possible.

[0071] 6. Apply optimal parameters.

[0072] Throughout this application, the term "output device" will mean any device that can be associated with processing a graphic object in a graphic file for its intended use, such as a display for displaying a graphic object, a printer for printing a graphic object, a plate-making machine for making a printing plate for later printing a graphic object, or a cutter for cutting a material in a shape corresponding to a graphic object. Although described as examples based on embodiments, the present invention is not limited to these examples.

[0073] It is well known in the art that there are any number of ways to represent computerized instructions that can be read by a computer to generate an output corresponding to a graphic file. The present invention is not specific to any particular way of representing instructions, nor does the present disclosure describe in detail how output devices format, store, or process these instructions, all of which are well known to those skilled in the art and well documented in the literature. Regardless of how the various graphic objects are represented by corresponding software for generating such objects or in stored instructions for instructing the software, it is well known that each graphic object corresponds to instructions that can be executed by a computer to produce a tangible result, whether that result is a display, a printed page, a printed plate, a slice of material, or any other type of output. There are already multiple systems for interpreting these computerized instructions into a format used by an editor to manipulate the graphic objects represented by these instructions. The present invention is not limited to any particular system for interpreting or editing such instructions. Instead, the present invention is directed to the following manner: existing editors can process information data associated with graphic objects in the described manner to modify portions of those objects according to certain predefined rules.

[0074] Specifically, embodiments of the present invention include methods for detecting and processing thin portions of selected graphical objects. Methods for performing such detection and processing of graphical objects may be applied to the entire file, or to a portion of a file selected automatically or by a user, such as a portion of a display that a user highlights viewable through a user interface. Computerized algorithms for selecting portions of a graphical file using a user interface are well known in the art. A graphical object may be represented by one or more outline paths defining an outline, which may be filled or unfilled. For graphical objects stored in a format that does not include a defined object outline, a preliminary method step may include converting the graphical object to an outline format. Computerized processes for performing such conversions are well known in the art.

[0075] The first step in the exemplary embodiment includes viewing the selected graphic objects and evaluating them to determine whether all parts of the object meet predetermined criteria. The predetermined criteria may include a threshold thickness corresponding to a resolution limit. Anything below the threshold thickness is characterized as a "thin" portion herein. The resolution limit may be a predetermined limit corresponding to the capabilities of the output device or may be a user-defined limit. Additional criteria may be used to identify thin portions that are subject to correction or that should not be corrected. Regardless of the specific criteria, various embodiments of the present invention generally include identifying particularly thin portions of a graphic object and subsequently thickening them to meet the defined resolution limit.

[0076] In a preferred embodiment of the present invention, the target graphic object includes text characters, such as but not limited to Latin characters and non-Latin characters, such as Asian characters or Arabic characters. These text characters may contain many thin parts, which may produce undesirable results on the gravure printing machine. However, it should be understood that embodiments of the present invention are not limited to text characters, any specific type of text characters, or any specific type of output device or technology, and embodiments of the present invention can be used to detect and modify all types of graphic objects.

[0077] The invention is not limited to any particular algorithm for generating a skeleton or any particular type of skeleton corresponding to a graphical object.

[0078] The method steps described herein may also include sending the output file with the modified features to an output device for further processing (such as printing, displaying, making printing plates, or cutting).

[0079] The output file including the modified graphic objects may include one or more layers. In an exemplary embodiment, the first layer may include the graphic objects before the thin part is identified and modified, and the second layer may include only the modification to the thin part. Such an embodiment may allow the user to view the modification compared to the original through the user interface, and if necessary, make additional manual adjustments. For example, various standards for determining the part to be adjusted of the graphic feature are discussed below. The user can run a set of standards, use these standards to detect the modification compared to the original, and then decide to apply additional or different standards. The standard can be applied to the entire graphic file, or it can be applied to the sub-portion of the file selected by the user. The user may even be able to select a single graphic feature to apply the selected standard. Saving the modification in a separate layer allows the modification to be easily identified for later viewing.

[0080] In some exemplary embodiments of the present invention, characteristics of modified graphical objects (e.g., characteristics of text characters in a particular font) may be stored for future use, such as as part of a font file. For example, the method steps described herein may be performed on a particular font set, such that each time the system encounters a recognized character in that font, the previously stored information may be accessed, thereby obviating the need to repeatedly perform the method each time the same character is encountered. Such storage of modified graphical objects corresponding to a certain input graphical object may be long-term storage, where the system saves such information for future use in conjunction with the same graphical features encountered in, for example, a different project associated with a particular output device, or it may be short-term storage, where the information is saved for use only within the same file or in conjunction with a single project corresponding to multiple files.

[0081] Finally, it will be appreciated by those skilled in the art that embodiments of the present invention relate not only to methods for performing the foregoing steps (such as with a computer or other processor), but also to systems (including such printers or processors) for performing the methods. For example, the methods may be performed by a processor programmed with instructions corresponding to the method steps described herein. Embodiments of the present invention also include computer-readable media, the computer-readable media including: program instructions, which, when executed by a processor, cause the processor to perform the method steps; and a processor so programmed. Additional embodiments include systems, the systems including: such a programmed processor; and an output device, the device being connected to the processor for receiving an output file and creating an output corresponding to the file.

[0082] Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made to the details within the scope and range of equivalents of the claims and without departing from the invention.

Claims

1. A method for proofreading at least a selected portion of a graphic data input file for output to an output device, the method comprising automatically adjusting at least one graphic feature in the input file to compensate for a predetermined resolution limit using a computer, the computer being programmed to perform such adjustment, the method comprising the steps of: (a) automatically identifying, using the computer, one or more portions in the selected portion of the input file having an initial coarseness less than the predetermined resolution limit; (b) automatically determining a set of optimal anisotropic migration parameters which, when applied, will bring the one or more portions above the predetermined resolution limit with a minimum total migration value; (c) automatically modifying, using the computer, the selected portions of the input file so that the adjusted coarseness of the identified one or more portions is greater than the initial coarseness, the modifying comprising applying an offset using the identified set of optimal anisotropic offset parameters; as well as (d) creating, using the computer, an output file comprising the at least one graphical feature having the adjusted thickness, Wherein, applying the offset using an identified set of optimal anisotropic offset parameters includes: applying ellipses to the selected portion of the input file, wherein each ellipse has an offset distance D in the major diameter direction, another offset distance d in the minor diameter direction perpendicular to the major diameter direction, and an angle α of the major diameter direction relative to the transverse direction, wherein D>d.

2. The method of claim 1, wherein the step of automatically determining a set of optimal anisotropic migration parameters comprises analyzing the results of a skeletonization operation.

3. The method of claim 2, wherein the step of analyzing the result of the skeletonization operation comprises: (i) constructing a 2-dimensional histogram representing the stroke direction divided into 180 / n direction intervals of n degrees each and k weight intervals equally divided in the range between 0 and the predetermined resolution limit, wherein the value of each cell in the interval comprises the total stroke length of the identified portion of the document having the stroke direction and the weight defined by the cell, and (ii) iteratively testing a plurality of offset conditions until a total stroke length represented by the sum of all cells in the histogram is less than or equal to a predetermined percentage of the total stroke length of all strokes in the identified portion.

4. The method of any one of claims 1-3, wherein the offset is applied by modifying or adding a vector map.

5. The method of any one of claims 1-3, wherein the at least one graphical feature comprises a text character or a portion thereof.

6. The method of claim 5, wherein the at least one graphical feature comprises a non-Latin text character.

7. The method of claim 5, wherein the selected portion includes one or more numeric characters representing text having a common size and a common font.

8. The method according to any one of claims 1 to 3, wherein the method further comprises: In a first instance, information identifying the adjustment made to compensate for the predetermined resolution limit of the graphical feature is stored in the computer in association with the graphical feature; and in a second instance, the stored information is used when the same graphical feature is encountered.

9. The method of claim 8, wherein the selected portion includes one or more numeric characters representing a font set, and storing the information identifying the adjustment includes storing a modified font set.

10. The method of claim 8, wherein the information identifying the adjustment is stored in a short-term computer memory storage device, and the first instance and the second instance are encountered while processing a single input file or multiple input files associated with a single project.

11. The method of claim 8, wherein the information identifying the adjustment is stored in a long-term computer memory storage device, and the first instance and the second instance relate to a first input file and a second input file processed for use in conjunction with the output device.

12. The method of claim 5, wherein the offset is applied to a rasterized version of the text.

13. The method of any of claims 1-3, further comprising receiving as user input the identification of the selected portion of the input document.

14. The method of any of claims 1-3, further comprising receiving the predetermined resolution limit as user input.

15. The method of claim 14, wherein the predetermined resolution limit is a user imposed limit.

16. The method of claim 14, wherein the predetermined resolution limit is defined by the output device having a resolution limit lower than a resolution limit of the input file.

17. The method of any one of claims 1-3, wherein the selected portion of the input file includes a plurality of strokes, the one or more portions include strokes less than all of the plurality of strokes, and the step of automatically modifying includes applying the offset to all of the plurality of strokes.

18. A system for proofreading at least a selected portion of a graphic data input file for output to an output device, the system being configured to automatically adjust at least one graphic feature to compensate for a predetermined resolution limit, the system comprising a controller, the controller comprising a processor having a memory, the processor being programmed with instructions for performing the following method steps: (a) automatically identifying, using a computer, one or more portions of said selected portion of said input document having an initial coarseness less than said predetermined resolution limit; (b) automatically determining a set of optimal anisotropic migration parameters which, when applied, will cause at least a selected percentage of the one or more portions to be above the predetermined resolution limit with a minimum total migration value; (c) automatically modifying, using the computer, the selected portions of the input file so that the adjusted coarseness of the identified one or more portions is greater than the initial coarseness, the modifying comprising applying an offset using the identified set of optimal anisotropic offset parameters; and (d) creating, using the computer, an output file comprising the at least one graphical feature having the adjusted thickness, in, Applying an offset using an identified set of optimal anisotropic offset parameters includes applying ellipses to the selected portion of the input file, wherein each ellipse has an offset distance D in the major diameter direction, another offset distance d in the minor diameter direction perpendicular to the major diameter direction, and an angle α of the major diameter direction relative to the transverse direction, wherein D>d.

19. The system of claim 18, further comprising the output device.

20. The system of claim 19, wherein the output device comprises a printer, a printing plate maker, or a cutter connected to the controller.

21. A non-transitory computer readable medium comprising program instructions for proofreading at least a selected portion of a graphic data input file for output to an output device, the instructions being programmed to automatically adjust at least one graphic feature in the input file to compensate for a predetermined resolution limit, the program instructions being operable when executed by a processor to cause the processor to perform the following steps: (a) automatically identifying, using the computer, one or more portions of the selected portion of the input document having an initial coarseness less than the predetermined resolution limit; (b) automatically determining a set of optimal anisotropic migration parameters which, when applied, will cause at least a selected percentage of the one or more portions to be above the predetermined resolution limit with a minimum total migration value; (c) automatically modifying, using the computer, the selected portions of the input file so that the adjusted coarseness of the identified one or more portions is greater than the initial coarseness, the modifying comprising applying an offset using the identified set of optimal anisotropic offset parameters; as well as (d) creating, using the computer, an output file comprising the at least one graphical feature having the adjusted thickness, Wherein, applying the offset using an identified set of optimal anisotropic offset parameters includes: applying ellipses to the selected portion of the input file, wherein each ellipse has an offset distance D in the major diameter direction, another offset distance d in the minor diameter direction perpendicular to the major diameter direction, and an angle α of the major diameter direction relative to the transverse direction, wherein D>d.

22. A computer program product comprising program instructions, which, when executed by a processor, cause the processor to perform the method of any one of claims 1-17.

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