RU2469399C1 - System and method of draft mode printing by means of conversion of pictures into contour sketches - Google Patents

Abstract

FIELD: printing industry.

SUBSTANCE: method of draft mode printing is carried out by means of conversion of pictures into contour sketches. At first graphic primitives are extracted from a flow of printed data or a printing task. Then the above graphic primitives are combined into pictures in accordance with their geometrical proximity. Then the produced pictures are converted into contour sketches. Afterwards a flow of printed data or a printing task is modified by replacement of a part of graphic primitives with produced contour sketches. Further the modified data flow or printing task is printed.

EFFECT: saving ink, toner of a printing device without loss of recognisability of printed images.

8 cl, 14 dwg

Description

The invention relates to the field of digital printing, and more particularly to resource-saving technologies in digital printing, in particular to systems and methods for cost-effective draft printing aimed at saving ink (or toner) of a printing device.

Modern printers and print drivers have the so-called draft mode. This mode involves reducing the print quality of text and images in order to save printing ink (toner). At the same time, various transformations of the data sent to the printing device are used for this purpose.

Data output to a printing device may be presented either in the form of a metafile or in the format of a page description language (PDL). A specific example of a metafile is Microsoft EMF, examples of page description language are Postscript and PCL. The PDF format, originally intended to describe pages, is now also used as a metafile on a number of operating systems.

Any of the above formats implies that the data is grouped into separate records (also referred to as “commands” or “tags”) specific to text, bitmap images and vector graphics. Ultimately, all this data is rasterized and printed. Therefore, it is possible to achieve the desired changes in the printed page by making changes to the metafile or page description language entries. This approach allows you to control the printing process, in particular in draft mode.

It is known from the prior art to apply an approach based on the selective preprocessing of data according to their type. So, for example, separate processing methods for various types of records in the stream of printed data are proposed in the application for US invention No. 20100214614 [1]. A similar approach is described in US applications No. 20100128287 [2], 20050063749 [3], 20090290883 [4]. It should also be mentioned the approach described in application for US invention No. 20090195811 [5], in which it is proposed to exclude from the printing process previously recognized data of certain types. Closest to the claimed invention is the approach described in US patent No. 6761422 [6], which proposes a preliminary separation of the printed data into typical objects with the appointment of specific rules for rasterization and printing for different types of objects.

Serious flaws are inherent in all known solutions. In particular, as a rule, all methods of draft printing are based on a decrease in the density of shading of the image, which inevitably leads to a deterioration in visual quality. At the same time, the saving of printing ink (toner) with this approach is small, since the areas of the drawing area, rather than the lines, are still painted over.

Additional problems arise due to the fact that data that visually looks like “pictures” can be represented not only as whole raster images, but also as a set of separate graphic elements, in particular, as vector graphics. Since in this case the picture is a set of disparate elements, this data cannot be directly processed as a whole, as a single "picture". In this case, the individual rules prescribed by various methods for economical printing of images, proposed in the above applications, are useless, as they apply to the whole image, and not to individual elements (lines, elementary forms).

Moreover, for composite (in particular, vector) graphics, problems arise not only when trying to apply individual rules for printing images, but also when transforming such composite graphics into a contour sketch. Individual graphic primitives may be “too elementary” for such a transformation. In fact, such a conversion is not applicable, for example, to a primitive that is a small bitmap image - a strip with a width of one pixel. The conversion can only be applied to the whole picture as a whole. In such situations, disparate graphic elements should first be grouped into pictures, and then they should be converted to outline sketches for these pictures.

The problem to which the claimed invention is directed is to develop such a method that would allow to achieve significant savings in consumables for draft printing, namely, saving printing ink / toner without losing recognition of the printed pictures, as well as a system that implements this method.

The technical result is achieved through the application of the proposed method, based on the conversion of printed pictures into contour sketches (“sketches”). In this case, the method of draft printing by converting images to contour sketches consists in the following operations:

- extract graphic primitives from the stream of printed data or from a print job;

- combine the above graphic primitives into pictures in accordance with their geometric proximity;

- convert the resulting pictures into contour sketches;

- modify the flow of printed data or the print job by replacing at least part of the graphic primitives with the resulting outline sketches;

- print a modified data stream or print job.

As for the system that implements the inventive method of draft printing by converting pictures into contour sketches, such a system is characterized in that it contains:

- a module for analyzing records of a stream of printed data or a print job, configured to analyze such records by dividing them into graphic primitives and other records, followed by transferring the selected graphic primitives to the module for combining graphic primitives and to the final assembly module, and other records are transmitted only in the final assembly module;

- a module for combining graphic primitives, configured to receive the above graphic primitives, combining them into pictures in accordance with their geometric proximity and transferring the resulting pictures as groups of graphic primitives to a module for converting pictures into contour sketches;

- a module for converting pictures into contour sketches, configured to receive pictures represented by groups of combined graphic primitives, converting them into contour sketches by selecting contours in them and transferring the resulting contour sketches to the final assembly module;

- a module for the final assembly of a print job, configured to receive sketches from the module for converting pictures to contour sketches, and receive from the analysis module records of all other records of the original job, as well as the formation of a modified print job by replacing at least some of the graphic primitives on the received outline sketches with the subsequent transfer of the modified task to the rasterization and printing module;

- a rasterization and printing module, configured to receive a modified print job, rasterize and print it.

Hereinafter, the term “outline sketch” (“sketch”) is used to refer to an image that looks like a pencil drawing of the contours highlighted in the original image (see Figure 1, which shows an example of the original image and the outline sketch obtained from it).

The essence of the claimed invention is explained below with the involvement of graphic materials.

Figure 1. Illustration for a contour sketch.

1.1 is the original image.

1.2 - a contour sketch obtained from the original image (looks like a pencil sketch of the original image).

Figure 2. The block diagram of the preferred implementation of the proposed method.

Figure 3. Modification of a print job presented as a metafile for one printed page.

Figure 4. Illustration of the impossibility of autonomous construction of contour sketches for individual graphic primitives without taking into account the whole picture as a whole. Example: a picture consisting of colored rectangles without clearly marked borders.

Figure 5. Illustration of the impossibility of autonomous construction of contour sketches for individual graphic primitives without taking into account the whole picture as a whole. Example: a picture consisting of raster images representing single rows of pixels.

6. Definition of a picture in accordance with the perception of human vision.

6.1 - the human eye distinguishes four separate pictures on the page shown, despite the fact that some of them consist of several graphic primitives.

6.2 - several separately located graphic primitives are perceived by the human eye as a whole picture.

7. The described rectangle as an example of the localization boundary for graphic primitives.

Fig. 8. Graphic primitives are combined if their localization zones (the described rectangles) overlap.

Fig.9. Graphic primitives are combined if their localization zones (the described rectangles) are located “close enough” - within the prescribed permissible distances. Subject to tolerance, graphic primitives can be combined even if they do not have a strict overlap.

Figure 10. One iteration of grouping graphic primitives. This procedure is an integral part of the process that composes graphic primitives into pictures.

11. Illustration for iterations of grouping graphic primitives.

11.1 - two groups of combined graphic primitives are surrounded by the described rectangles;

11.2 - the two groups mentioned above are considered as new graphic primitives and are combined into an even larger group.

Fig. 12. The process of combining graphic primitives into pictures.

Fig.13. Illustration for the process of combining graphic primitives: one iteration reduces the number of newly obtained graphic primitives.

Fig.14. Draft printing system by converting pictures to outline sketches.

The inventive method includes sequential steps presented in the flowchart shown in Figure 2:

- a preliminary analysis of the data sent for printing is performed in order to identify graphic elements in them (step 201). In this case, the metafile (or page description language) records are recognized in accordance with the classifier of records adopted for this form of presentation. Identified records describing graphic primitives are retrieved from the data set for the purpose of their further processing. These entries can describe both raster images and vector graphics;

- identified graphic primitives are combined into pictures in accordance with their geometric proximity (step 202). The result of this action are groups of graphic primitives corresponding to the above pictures. This operation is performed by analyzing the coordinates of graphic primitives. Grouping primitives is necessary, since the subsequent creation of contour sketches is possible only for whole pictures, and not for disparate graphic elements. The results of combining primitives into groups are presented in the form of a formal description (the choice of the description form is arbitrary);

- for each created group of graphic primitives united in a picture, an outline sketch is created. This operation can be done, for example, by creating an auxiliary bitmap: the resulting group of graphic primitives is transformed into a bitmap (step 203). A contour sketch is constructed for the resulting bitmap image (step 204). To construct a contour sketch, any of the methods is used based on the selection in the drawing of lines in places of contrasting transitions and the suppression of areas with monotonous shading;

- the created outline sketch as a new record is added to the metafile (or page description language) that describes the data intended for printing. At the same time, at least part of the previous entries describing the graphic primitives combined into a picture is deleted. Thus, the data intended for printing is modified: the records of the graphic primitives grouped into the picture are replaced by the record of the outline sketch created on the basis of these elements (step 205). Incomplete deletion of source records is used in cases where it is necessary to partially save the original graphic primitives: for example, to leave those that formed the boundary frame of the picture;

- the modified data is output to a printing device (step 206).

It is assumed that the print job (print data stream) is represented by either a page description language (PDL) or a metafile. Such a structured representation contains entries (also referred to as “tags” or “commands”) describing text data and graphic primitives.

In a preferred embodiment, the described method uses a printer spool file as data. In this case, the printed pages form separate tasks and are represented by metafiles (EMF format in the Windows operating system) - one metafile for each printed page. The method is also applicable to other data presentation formats having a similar structure, for example, to PDF files.

The main purpose of the described method is to modify the print job for each page (presented, for example, in EMF format), as shown in Fig.3. The following is a more detailed description of the steps listed above.

At the first stage, the classification of metafile records (print jobs) is carried out in accordance with the specification of a particular data format. The preferred implementation uses the EMF format (Enhanced MetaFile), so records are classified according to the EMF specification. As a result, records are revealed - graphic primitives (these can be both raster images and elements of vector graphics).

After identifying graphic primitives, these primitives are grouped into pictures. This step seems necessary for the following reasons.

The printed metafile contains a mixture of records describing various graphic elements (primitives) - raster images, straight lines, curves, polygons, various shapes, etc. In the general case, these records are not arranged in objects, but lie in a metafile in random order. Therefore, the direct identification of graphic primitives in a metafile does not say anything about their relationship and the layout of pictures perceived by the human eye.

In the general case, the operation of constructing a contour sketch does not make sense for a single graphic primitive. It only makes sense for the picture as a whole. At first glance, this statement is not obvious, therefore, we confirm it with several examples.

The first example is a combination of colored rectangles touching the sides (Figure 4). In the source metafile, each such rectangle is a graphic primitive and is described by a separate entry. In this example, the rectangles do not have colored perimeters (frames), but contain only filled inner areas. It is impossible to talk about constructing a contour sketch by processing these rectangles separately: if we destroy the inner shading of each of them, then the whole picture will simply disappear. We won’t get grids from colored frames, as we would like when sketching.

The next example is a picture made up of small bitmap images, which are stripes with a width of one pixel (Figure 5). In the metafile, each such strip is represented by a separate entry. The operation of constructing a contour sketch cannot be applied to a single strip of pixels - this requires the whole picture as a whole, but the scattered metafile records do not give an idea of the whole picture.

A similar situation occurs when a picture is built on the principle of linocut - as a combination of individual color lines (stripes). Such "linocut" may consist, for example, of colored lines of vector graphics.

Finally, there may be a combination of any graphic primitives: for example, a raster image with vector graphics elements superimposed on it. In this case, when constructing a contour sketch, it is important to consider the combination of all these components of the picture.

The above examples show that the operation of constructing a contour sketch makes sense only for the picture as a whole, and not for individual graphic primitives (in the particular case, of course, a single primitive can be a bitmap image that is identical to the picture, but this does not always happen). That is why the process of grouping graphic primitives into pictures is required.

To better understand the above grouping operation, we will first explain the following concepts: what is the main property of a picture, what is the imposition of graphic primitives, what is one iteration of grouping graphic primitives, and how is the whole process of combining primitives into pictures based on it.

There is no exact definition for the term “picture”. Let us agree to understand by a picture such a combination of graphic elements (dots, spots, lines, shapes) on a plane that is visually perceived by the human eye as a whole. In other words, the main characteristic property of a picture is its integrity when perceived by the human eye. For example, Fig. 6.1 shows a printed page containing four pictures (in accordance with visual perception). In fact, only two of these pictures are literally bitmap images 101, and the other two pictures 102 are combinations of disparate graphic primitives - lines and elementary forms. Fig.6.2 illustrates the situation when several graphic elements are located at a distance from each other, but the human eye perceives them as a whole picture. The above illustrations demonstrate that the human eye easily combines graphic primitives into pictures.

The above detailed explanation of the concept of “picture” is important for understanding the further presentation of the method, since the operations of constructing a contour sketch are applicable specifically to pictures, and not to disparate graphic primitives.

Image integrity is a key property for grouping graphic primitives. The process is based on the idea of the geometric proximity of individual elements. It is believed that graphic primitives can be grouped into a picture if they geometrically overlap or are located “close enough” (proximity of a location can be expressed formally in terms of geometric distance).

The inventive method implies that the graphic primitives are provided with a description in the form of a set of geometric parameters. The form of such a description is arbitrary, but it includes at least the geometrical coordinates of the elements, which make it possible to calculate the localization of primitives on the plane. For example, for a raster image, such parameters are the coordinates of the vertices of the image rectangle. For elements of vector graphics, these can be the radii of circles and the coordinates of centers, the coordinates of the vertices of polygons, composite lines, etc. Units of measure for a geometric description can be arbitrarily selected: meters, millimeters, pixels. For example, in the described preferred implementation, pixels are used.

The description of a graphic primitive implies the determination of its localization zone. In the text of the document, we call this zone also the “boundary zone”, emphasizing with this name that the zone covers the graphic primitive from the outside. As such a boundary zone, any described polygon can be selected, covering the graphic primitive in accordance with the rules of geometry. In the preferred implementation, the described rectangles (bounding boxes) are used as boundary zones (Fig. 7), since this figure is the simplest from the point of view of calculations. These rectangles have sides parallel to the coordinate axes and are represented by the coordinates of their vertices. The above-mentioned "boundary zones" in the form of rectangles are used when comparing graphic primitives when grouping them into pictures.

The basic idea of grouping graphic primitives by their geometric proximity is to overlap (overlap) their “boundary zones”. In the preferred implementation, the following rule is used: two graphic primitives are considered to overlap if their boundary zones (the described rectangles) overlap (Fig. 8) or are located "close enough" in accordance with the specified allowable distances (Fig. 9). In a preferred implementation, these allowable distances are set separately for each of the two coordinates and are counted from the sides of the rectangles. Actually, the analysis of the intersection of two rectangles on a plane is a trivial geometric problem.

The stage of grouping graphic primitives into pictures is an iterative process. First, the original primitives are combined into groups, then the resulting groups are combined into even larger groups, etc.

One iteration of grouping graphic primitives is illustrated in the flowchart of FIG. 10 and consists of the following steps:

- the source data is a list of graphic primitives (step 1001); a list is also allocated to form groups, but at the initial stage it is empty;

- the next graphic primitive is extracted from the list of primitives (step 1003) for comparison with the list of received groups;

- if the list of groups is still empty, then the studied graphic primitive is considered as the first group included in the list (step 1005). This primitive is so far the only element in the group, and its boundary rectangle becomes the boundary rectangle of the created group. In this case, there is a return to the step of extracting the next primitive from the list (step 1003);

- if the list of groups is not empty, the studied primitive is compared with each group from the list (step 1004) until the fact of overlapping with one of the groups is detected (the overlap of the corresponding boundary rectangles is analyzed);

- if no overlap of the studied primitive was found with any of the groups, then it cannot be combined with any of the considered groups. In this case, the primitive under study forms a new group in the list (step 1005), its boundary rectangle becomes the boundary rectangle of the created group. In this case, there is a return to the step of extracting the next primitive from the list of primitives (step 1003);

- if an overlap of the studied primitive with one of the groups is detected, then the primitive is included in this group. The boundary rectangle of the group is modified - recalculated in such a way as to cover the new element included in it. Thus, in this case, the list of groups does not increase, but one of the groups is replenished with a new element (step 1006). In this case, there is a return to the step of extracting the next graphic primitive from the list of primitives.

- the process ends if all the primitives in the list of primitives are processed (step 1007). The result is a list of groups combining graphic primitives based on the principle of geometric proximity.

In a preferred implementation, when analyzing the overlapping of boundary rectangles, the possibility of their “close proximity” in accordance with a given allowable distance is taken into account. This accounting does not change the stages of the above process, but applies only to the stage of comparison of boundary rectangles.

The process described above is an integral part - one iteration - of the whole process of combining graphic primitives into pictures. If the obtained groups of primitives, in turn, overlap, then they can be combined into larger groups (the situation is illustrated in Fig. 11). That is why the complete process of combining graphic primitives into pictures contains many iterations described above.

The complete process of combining graphic primitives into pictures is illustrated in Fig. 12 and contains the following steps:

- at the initial stage of the process, all graphic primitives (for each of which its boundary rectangle is defined) are combined into a list and considered as candidates for grouping into pictures (steps 1201 and 1202);

- one iteration of combining graphic primitives into groups is performed (step 1203). The result is a list of groups combining graphic primitives;

- the conditions for completing the iterative process are checked (step 1205), these conditions are described in detail below;

- if the iterative process continues, then the resulting groups are considered as new graphic primitives (step 1206) and are used as input data for the next iteration. Thus, the next iteration creates a new list of groups (step 1202), as a combination of previously created groups (step 1204);

- step by step, each iteration reduces the total number of groups, combining in them an increasing number of source graphic primitives (the foregoing is illustrated in Fig.13);

- when the process ends as a result of checking the completion conditions, the final groups in the list are pictures formed from graphic primitives and can be used to obtain contour sketches (step 1207).

The termination condition (step 1205) implies the fulfillment of either of two rules:

- if only one group remains in the list of groups. This means that all graphic primitives are combined into one picture, and there is nothing more to group;

- if the number of groups received at the next iteration is equal to the number of source graphic primitives (or previously received groups). This means that the studied graphic primitives (or groups derived from them) are located far from each other and cannot be combined, i.e. form separate pictures.

As a result of the process described above, pictures (at least one) are obtained, presented as groups of graphic primitives, united on the basis of their geometric proximity. The inventive method does not regulate a specific formal description expressing the belonging of primitives to pictures. For example, in the preferred implementation, tables are used that describe both the geometric parameters of primitives and groups, as well as signs of their belonging to each other. As a result, each received group, combining graphic primitives, is treated as a picture and used to obtain a contour sketch.

The creation of contour sketches based on the obtained images can be performed both with the help of rasterization of these images into auxiliary raster images, and without it.

The approach without rasterization is applicable only for the special case when the picture consists of vector graphic elements that do not overlap and have distinct borders and filled inner areas. In this case, the shading of the inner areas is suppressed, and the borders of the vector elements are highlighted, as a result of which the combination of such modified graphic elements looks like a contour sketch when printing. But in the general case, this approach is not applicable.

In a preferred embodiment, auxiliary raster images for each of the obtained images are used to create an outline sketch (step 2003 in FIG. 2). In this particular case, an auxiliary raster image is obtained using the MS-Windows GDI (Graphic Device Interface) functions. The main stages of this process are listed below (similar functions are used for other operating systems, the whole approach remains the same):

- preparation (using the GDI functions) for the whole printed page of the so-called “Compatible DC (Device Context)” and “Compatible bitmap image” (internal image in memory);

- Playback of the metafile in the aforementioned “Compatible DC” (using the GDI functions), and all records except text ones are played back. Thus, the result is a bitmap image (in RAM) containing graphic elements and not containing text entries;

- allocation of auxiliary memory buffer corresponding to the received bitmap image of the page in size and resolution in pixels;

- transfer of the received raster image to the above auxiliary buffer;

- localization of individual images (as fragments of a common page raster image) in the above buffer and transferring them to separate local buffers. To localize fragments in the page buffer, the coordinates of the boundary (described) rectangles obtained earlier when grouping primitives into pictures are used: they just correspond to the required boundaries of the individual pictures in the page buffer;

The result is pictures presented as separate bitmap images. These images are used to create outline sketches.

In a preferred embodiment of the invention, a process is used to obtain an outline sketch, the steps of which are listed below (the process is suitable for both a color image and an image in grayscale or monochrome):

- preprocessing a bitmap image. In particular, in the preferred implementation at this stage, smoothing filtering, increasing contrast, highlighting the visual features of the image, for example, based on building a map of importance, is performed (see Wen-Fu Lee, Tai-Hsiang Huang, Yi-Hsin Huang, Mei-Lan Chu, and Homer H. Chen, SPIE-IS & T / Vol. 7240, 2009) [7];

- creating a copy of the image in grayscale (if the original image was originally presented in grayscale, this step is not required);

- selection of the contours in the resulting copy of the image in grayscale. Getting a binary mask that selects these contours and suppresses other parts of the image. In particular, in the preferred implementation, the detection of contours using Difference-of-Gaussians (DoG) and a threshold cutoff of the obtained values is used;

- application of the obtained binary mask to highlight contour lines in the above bitmap image. For color images, a mask is used for each color channel. The mask saves only those pixels of the image that correspond to the found contour lines. The result is an image - a contour sketch.

As mentioned earlier, getting an outline sketch based on a previously created bitmap is not the only possible approach. A different approach can be used in the particular case when the picture consists only of elements of vector graphics. In this case, it is possible not to obtain an auxiliary raster image and not to use the selection of contour lines by filtration methods. It is enough to suppress the inner shading of the elements of vector graphics and select their contour lines, if, of course, the data allow this. In this case, the result - a contour sketch - will be presented not in the form of a raster image, but as a combination of graphic primitives with changed characteristics. However, this approach is applicable only for special cases.

So, for each resulting image, contour sketches are created (in the preferred implementation, they are bitmap images). These contour sketches are used in the output print task as new graphic primitives instead of the original ones, on the basis of which the pictures were obtained. In a preferred implementation, modifying a print job involves creating a new metafile (EMF) instead of the original one, into which the resulting outline sketches are embedded as records using the graphical interface (GDI) functions. All other records of the source metafile (for example, describing text blocks) are copied to the above output metafile from the source. In this case, the original graphic primitives, on the basis of which pictures and contour sketches were created, are excluded from the output metafile (at least some of these primitives are excluded). In a preferred implementation, a portion of these primitives may optionally be stored; for example, horizontal and vertical lines forming table frames. In the described implementation, optional suppression of text and graphic records is also possible during the formation of a modified print job. As a result, the generated modified print job (metafile) is rasterized and printed.

On Fig presents a block diagram of the inventive system that implements the above method. The system contains the modules listed below:

- module 1401 analysis of the records of the original print job;

- module 1402 combining graphic primitives into pictures;

- module 1403 converting pictures into contour sketches;

- module 1404 of the final assembly of the print job;

- module 1405 rasterization and printing.

The initial data for the system is a print job represented by a page description language (PDL) or a metafile. The source data contains records describing, in particular, text elements, raster images and vector graphics elements. The output is a modified print job for use in cost-effective draft printing.

The record analysis module 1401 classifies the source data records in accordance with the specification of the metafile (or page description language). It extracts the entries of the graphic primitives and directs them to the module 1402 combining primitives into pictures and the module 1404 of the final assembly. All other records are sent only to the final assembly module 1404.

A module for combining graphic primitives 1402 groups these primitives into pictures based on their geometric proximity. This module operates in accordance with the process described above. The geometry of graphic primitives is analyzed; if the boundary (described) rectangles of primitives overlap or are located close enough to each other (in accordance with a given allowable distance), then such primitives must be grouped. The resulting groups of graphic primitives are treated as pictures, in the future, based on them, contour sketches are created.

The above images (represented by groups of combined graphic primitives) are supplied to the contour sketches conversion module 1403, which creates the aforementioned sketches (in the preferred implementation, contour sketches are bitmap images in which contour lines are highlighted and uniform filling of areas is suppressed). Created sketches are transmitted to assembly module 1404.

The final assembly module 1404 receives the received outline sketches from the image-to-thumbnail conversion module 1403 along with all other records of the original metafile classified by the analysis module 1401. He creates a modified print job, which is a new metafile, which includes the resulting outline sketches (in the form of records - bitmap images), as well as (optionally) other records received from the analysis module 1401. The final assembly module 1404 is configured to selectively suppress records of a particular type. For example, it suppresses at least part of the graphic primitives on the basis of which the outline sketches were created, since the resulting outline sketches are included in the output metafile instead of them. At the same time, part of the graphic primitives can be optionally saved: for example, horizontal and vertical lines forming a grid of tables.

The final assembly module 1404 sends the modified print job to the rasterization and printing module 1405. The rasterization and printing module 1405 rasterizes the modified data and prints it.

The proposed method and system are intended for use in printers and multifunction devices (color or monochrome) to provide an economical draft mode of printing (saving ink or toner). They can also be implemented in the drivers of the above devices.

The proposed method and system is applicable for all types of print jobs presented in a metafile format (for example, EMF, MS-EMFSPOOL) or a page description language (such as PCL, PS, PDF), since all these formats are based on the presentation of data in the form records (“tags”) describing text data, bitmap images and vector graphics.

It should be noted that the above embodiment of the invention was set forth for purposes of illustration, and it should be apparent to those skilled in the art that various modifications, additions and substitutions are possible without departing from the scope and meaning of the present invention as claimed in the appended claims.

Claims (8)

1. The method of draft printing by converting images into contour sketches, which consists in the following operations:
- extract graphic primitives from the stream of printed data or from a print job;
- combine the above graphic primitives into pictures in accordance with their geometric proximity;
- convert the resulting pictures into contour sketches;
- modify the flow of printed data or the print job by replacing at least part of the graphic primitives with the resulting outline sketches;
- print a modified data stream or print job. 2. The method according to claim 1, characterized in that the graphic primitives are combined into pictures by performing the following operations:
- find for graphic primitives external borders in the form of the described rectangles;
- combine those graphic primitives in which the described rectangles overlap. 3. The method according to claim 1, characterized in that the graphic primitives are combined into pictures by performing the following operations:
- find for graphic primitives external borders in the form of the described rectangles;
- designate tolerances for the proximity of the primitives in the form of distances by coordinates;
- combine those graphic primitives in which the described rectangles either overlap or are located so close to each other that their sides are spaced less than the assigned tolerances. 4. The method according to claim 1, characterized in that the conversion of the above received images into contour sketches consists in performing the following operations:
- each of the above images, presented as a combination of graphic primitives, is rasterized into an auxiliary raster image;
- convert the constructed raster image into a contour sketch. 5. The method according to claim 4, characterized in that the resulting raster images are converted into contour sketches in a manner consisting of the following steps:
- for each of the above raster images build a copy of it in gradations of shades of gray;
- in the obtained copy of the image in shades of gray, the contours are detected and a binary mask is constructed that selects these contours and suppresses other parts of the image;
- form a contour sketch by applying the resulting binary mask to the above bitmap image. 6. The method according to claim 1, characterized in that the conversion into a contour sketch of the graphic primitives combined into a picture is performed by directly selecting the boundary lines and suppressing the shading of the inner areas in the above graphic primitives. 7. The method according to claim 1, characterized in that when modifying the stream of printed data or a print job, the modified data includes those original graphic primitives that are horizontal or vertical lines in an unreformed form. 8. The system of draft printing by converting pictures into contour sketches, characterized in that it contains:
- a module for analyzing records of a stream of printed data or a print job, configured to analyze such records by dividing them into graphic primitives and other records, followed by transferring the selected graphic primitives to the module for combining graphic primitives and to the final assembly module, and other records are transmitted only in the final assembly module;
- a module for combining graphic primitives, configured to receive the above graphic primitives, combining them into pictures in accordance with their geometric proximity and transferring the resulting pictures as groups of graphic primitives to a module for converting pictures into contour sketches;
- a module for converting pictures into contour sketches, configured to receive pictures represented by groups of combined graphic primitives, converting them into contour sketches by selecting contours in them and transferring the resulting contour sketches to the final assembly module;
- a module for the final assembly of a print job, configured to receive thumbnails from the module for converting pictures to contour sketches and receive from the analysis module records of all other records of the original job, as well as the formation of a modified print job by replacing at least some of the graphic primitives with received outline sketches, with subsequent transfer of the modified task to the rasterization and printing module;
- a rasterization and printing module, configured to receive a modified print job, rasterize and print it.

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