RU2405201C1 - Method and system for reducing ink consumption when printing - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: system for reducing ink consumption when printing by rasterising font includes a font rasteriser which can rasterise a character from a description contained in the font into a bitmap based on current font parametres such as the transformation matrix and text effects; a character code, font and font parametres are transmitted to the input of the rasteriser. The bitmap is transmitted to a module for re-colouring fragments to the background colour and dimensions of the bitmap are transmitted to a random number generator, the module for re-colouring fragments to the background colour which can re-colour small fragments to the background colour in random coordinates of the bitmap of the character in accordance with the disclosed method; a bulk map of the character is transmitted to the input of the module from the font rasteriser, as well as random coordinates inn the bitmap of the character from the random number generator, masks M1 and M2 defined by print resolution, parametre N which gives the degree of saving ink. The module for re-colouring fragments can send a request for receiving random coordinates to the random number generator; the bitmap with the re-coloured fragments of the background is transmitted to font cache, the font cache can realise functions of random access memory for storing bitmaps of characters rasterised for the printed page or the entire printing task.

EFFECT: reduced consumption of ink with output of text or image onto a printer.

8 cl, 6 dwg

Description

The invention relates to the field of digital printing, in particular to systems and methods for saving ink when printing text or images to a printer, and can find application in operations related to the implementation of a significant amount of printing work.

In the description of the invention, the term toner is also used as a synonym for ink, which should be understood as a generic name for any type of ink used in printing, including dye powder, liquid ink, etc.

Various approaches to solving the problem of saving toner in printing devices are known from the prior art, of which technical solutions based on special processing of a rasterized image of a printed page are of the greatest interest. A common practice when printing in draft mode is to reduce the optical density of the entire image when it is rasterized. For electrophotographic and inkjet printing devices, a decrease in optical density is achieved by increasing the brightness of the pixels of the rasterized graphic objects prior to rasterization, which uses half-tinting, or by changing the thresholds of half-tinting. For example, US Pat. No. 5,646,670 provides a device and method for reducing ink consumption by reducing the optical density for an entire printed color image. US Pat. No. 5,946,450 describes a method for reducing toner or ink consumption in a rasterized image by changing the level transfer function, which brightens the entire image. US patent 6476836 describes an image forming apparatus in which image pixels having values greater than a threshold are converted to a predetermined pattern obtained by pulse width modulation, and image pixels having values less than a threshold are not printed. Decreasing the optical density for the entire page significantly affects print quality: text characters acquire torn edges, text looks noticeably worse than printed in normal mode, eyes get tired of reading such text, sometimes such text is not recognized by optical character recognition programs, photos are noticeably distorted.

To improve the appearance of printed pages and, first of all, improve the quality of the text, there are several approaches to protect the edge points of the printed areas and reduce the optical density only for the internal pixels of these areas. US patent 5483625 proposes to reset the values of points in a rasterized image according to a given (regular) pattern, but the edge points of the connected areas, including characters, remain unchanged. Thus, within the connected areas, a regular structure (texture) is formed, formed by fragments of the background. US patent 6266153 and US patent 7330288, which is selected as a prototype of the claimed invention, describe methods for reducing the optical density only for the internal points of the connected areas. Pages printed using the above methods look better, but the texture inside the areas is clearly visible, sometimes the text processed in this way is not recognized by optical character recognition programs, halftone photographs and regions filled with gradient fills are distorted, and especially distorted when color printing is made, since it becomes probable occurrence of color distortion.

To save toner, a special TrueType font called Ecofont was proposed. Thanks to the openings inside the font’s description, up to 20% savings are achieved in comparison with solid characters. Ecofont can be considered a good solution for rough office printing, but otherwise this font has many drawbacks: Ecofont contains only one headset and supports only European languages based on the Latin alphabet, Ecofont does not look good on PC screens and on printed documents for character sizes over 30 typographic points, in addition, characters larger than 30 typographic points are not recognized by optical character recognition programs, the degree of toner saving is not regulated in any way.

Existing approaches have two main disadvantages:

- the appearance of a document printed in economy mode is noticeably worse than a document printed in normal mode;

- Processing a whole rasterized page requires significant computing resources or additional equipment.

Most defects that occur are listed above. The most serious are the following: halftone photographs and areas filled with gradient fills are distorted, the text remains readable, but looks much worse than solid black text. Figure 1 shows an example of 14-point text printed in various ways. The page with the text was scanned at a resolution of 600 dpi, respectively, in FIG. 1, the text is shown enlarged approximately 6 times. Figure 1.1 shows the result of increasing the brightness of the entire image by 25%, which for electrophotographic and inkjet printers is achieved by half-toning; Figure 1.2 is the result of increasing the brightness by 25% only for the internal points of the characters, and the edge points do not change; Figure 1.3 is a text printed in Ecofont font; Figure 1.4 is a print result in solid black without saving toner. All of the above methods for modifying characters are clearly visible compared to the normal printing mode.

Figure 2 shows a simplified processing scheme for saving toner in existing methods. As a rule, the entire rasterized image is processed, and in the case of a color image, bitmaps for each ink used in printing are processed. This scheme corresponds to the screening scheme in standard printing protocols such as Postscript and PCL. Images, vector primitives, such as straight lines and curves, text are rasterized separately from each other, and then copied to the bitmaps of the page. Rasterizing a font from a vector description, such as TrueType and PS Type 1, into a bitmap requires significant computational resources. For this reason, bitmap processors (RIP) for both Postscript and PCL use a font cache to store bitmaps of rasterized characters. Additional processing aimed at saving toner is carried out after bitmaps for the whole page or its significant part are formed. The bitmap for the entire page is large, it takes considerable time to process it.

The present invention solves the problem of reducing toner consumption while maintaining high print quality.

The technical result is achieved by developing an improved method for rasterizing fonts and a system that implements the inventive method. At the same time, a system is proposed that includes:

- a font rasterizer configured to rasterize a character from a description contained in a font into a bitmap based on the current font settings, such as the transformation matrix and text effects; at the same time, the character code, font and font parameters are received at the input of the rasterizer; the bitmap is transferred to the fragment repainting module in the background color, and the sizes of the bitmap are transferred to the random number generator;

- module repainting fragments in the background color, configured to repaint the background color of small fragments in random coordinates of the bitmap symbol in accordance with the claimed method; the bitmap of the symbol from the font rasterizer, random coordinates in the bitmap of the symbol from the random number generator, masks M1 and M2, determined by the print resolution, parameter N, setting the degree of ink saving; wherein the fragment repainting module is configured to transmit a request for random coordinates to a random number generator; a bitmap with repainted background fragments is transferred to the font cache;

- a font cache configured to perform functions of random access memory for storing bitmaps of symbols rasterized for a printed page or the entire print job.

Such a system is intended to implement the proposed method of reducing ink consumption during printing by rasterizing fonts, which consists in performing the following operations:

- convert a character from a vector description contained in a font into a bitmap;

- generate N pairs of random coordinates (x, y) in the bitmap, where x is the column number, y is the row number;

- for each pair of coordinates (x, y), the first fragment of the bitmap F1 is compared with the center at the point with coordinates (x, y) and size N1 by N2 with the first mask M1; and replace the second fragment of the bitmap F2 centered at the point with coordinates (x, y) and size K1 by K2 with the second mask M2 if F1 and mask M1 match;

- save the character bitmap to the font cache.

In other words, the claimed method overcomes the main disadvantages of existing solutions by adding small fragments of the background to random positions of the bitmap in the inner areas of the characters during the rasterization of the character and saving this bitmap to the font cache.

Further, the essence of the claimed invention is disclosed in more detail using graphic materials.

Figure 1 - scanned fragments of text printed using known and claimed methods of saving toner.

Figure 2 is a simplified diagram of a traditional approach to saving paint due to special processing in a raster image processor (RIP).

Figure 3 - scheme of saving paint due to the claimed rasterization of fonts in the raster image processor.

Figure 4 - the main steps of the method of saving ink when printing through the claimed font rasterization.

Figure 5 - blocks of a system for saving ink when printing through the claimed font rasterization.

6 is a diagram of a module for repainting fragments of a bitmap of symbols in the background color.

Figure 3 shows the proposed font saving scheme in a raster image processor (RIP). Only characters of the text are processed, moreover, the processing of each character for a given font and size is performed only once, which allows to achieve a very high processing speed. The speed gain is especially noticeable for color images, since existing methods process large bitmaps of a page for each ink, and in the proposed method only small bitmaps of rasterized symbols are processed. This approach does not distort halftone images and vector graphics. Reduced ink consumption is adaptive to page content and can reach 20% for typical office documents. Unlike known methods, the proposed method does not automatically save toner for small-sized characters without introducing any additional thresholds. The quality of small characters does not deteriorate. In appearance, the processed characters are almost indistinguishable from solid black characters. This is due to the random coordinates of small fragments of the background embedded in the inner areas of the characters. Figure 1 (view 1.4) shows an example of processing for saving toner by the proposed method, Figure 1 (view 1.5) shows solid black symbols. On the printed page, the difference between Figure 1 (view 1.4) and Figure 1 (view 1.5) is almost invisible to the naked eye: small fragments of the background are noticeable only upon careful examination, the readability of the text is almost not worsened, optical character recognition programs normally recognize the processed by the proposed method text. The degree of toner saving or the brightness / contrast of characters can be flexibly adjusted. In contrast to the Ecofont font, the proposed solution works for fonts of any typefaces and characters of any language.

Figure 3 shows the location of the proposed method in the process of rasterization of the printed page. Text characters are processed in steps 304, 305, and 306. Step 304 is to rasterize a character from a bitmap description into a bitmap of the desired size. Adding small fragments of the background to random positions inside the characters is performed in step 305. The rasterized bitmap of the symbol with embedded fragments of the background is stored in the font cache in step 306.

A method of saving ink when printing by the claimed font rasterization is shown in FIG. 4. The conversion of the font symbol from the vector description to the bitmap is performed at step 401. At step 402, N pairs of random coordinates (x, y) are generated inside the symbol bitmap. At step 403, for each pair of (x, y) coordinates, the first fragment of the bitmap F1 with the center at the point with coordinates (x, y) and the size N1 by N2 with the first mask M1 is compared and the second fragment of the wholesale card F2 with the center at the point coordinates (x, y) and size K1 on K2 to the second mask M2, if the fragment F1 and the mask M1 coincide. Saving the character bitmap to the font cache is performed in step 404.

The invention can be implemented in the embedded software of raster image processors (RIP) printers and multifunction devices, or can be implemented in the form of an electronic circuit. Figure 5 shows the General scheme of the proposed system. The font rasterizer (501) rasterizes the character from the vector description contained in the font to the bitmap, taking into account the current font settings, such as the transformation matrix and text effects, such as underlining or strikethrough. The rasterizer input receives the character code, font, and font settings. The bitmap of the symbol is transferred to the fragment repainting module in the background color (502), and the sizes of the bitmap are transferred to the random number generator (503).

The module for repainting fragments in the background color repaints small fragments in random coordinates of the bitmap of the symbol in the background color in accordance with the claimed method. The symbol bitmap from the font rasterizer, random coordinates in the bitmap of the symbol from the random number generator, masks M1 and M2, which depend on the print resolution, parameter N, which controls the degree of ink saving, are received at the module input. The fragment repainting module in the background color sends a request for random coordinates to a random number generator. A bitmap with repainted background fragments is transferred to the font cache (504). A font cache is RAM for storing bitmaps of characters that are rasterized for a printed page or the entire print job.

A possible implementation of the module repainting fragments of the bitmap symbols in the background color is shown in the diagram in Fig.6. The subtracting counter (601) generates N queries for random coordinates (x, y). The request is transmitted through a comparator (602) and an inverter 603. The counter is clocked by a sync generator (604). The comparator compares the counter output to zero. The inverter inverts the output signal of the comparator, and this signal is a request for random coordinates. Random access memory (605) stores the bitmap of the character. From the memory, you can extract a fragment of a bitmap F1 of size N1 to N2 centered at a point with coordinates (x, y) and you can replace a fragment of a bitmap F2 of size K1 with K2 centered at a point with coordinates (x, y) with a mask M2 if the signal from the mask comparator (606) is equal to a logical unit. The symbol bitmap, mask M2, random coordinates (x, y), and a signal from the mask comparator are received at the input of the RAM. The mask comparator compares the fragment of the bitmap F1 with the center at the point with coordinates (x, y) and the size N1 on N2 with the mask M1 and outputs a logical unit if F1 and M1 match. The output of the mask comparator is associated with RAM. A fragment of the bitmap of the symbol F1, mask M1, and random coordinates (x, y) are received at the input of the mask comparator. We also note that it is clear to a specialist that any of the above modules can be implemented as a microprocessor system containing a processor and memory.

In a preferred embodiment of the invention, there are a number of important additional features. The dimensions and aperture of the M1 and M2 masks depend on the print resolution and type of printer. The size of the mask M1 is always larger than the size of the mask M2. The M2 mask contains a background fragment. For example, to print at 600 dpi, the M1 mask looks like this:

x111x

11111

11111

11111

x111x

where x can have any value, 1 denotes a printable point, and 0 denotes a non-printable point, that is, a background.

mask M2 has the following form:

101

000

101.

The initial number of the random number generator depends on the size of the character bitmap. N is equal to the number of pairs of random coordinates that are generated iteratively. Changing N allows you to control how much toner is saved. The value of N lies in the range from W / 64 to 2W, where W is the total number of pixels in the character bitmap.

It should be noted that in a user-defined font, such as Postscript Type 3, the symbol can be any part of the printed page, including the entire printed page.

The proposed method and system are intended for use primarily in color and black and white electrophotographic and inkjet printers and multifunction devices. In addition, the invention can be used in any printing device. Toner reduction up to 20% for typical office documents without a noticeable decrease in print speed. The proposed method does not lead to the appearance of visible artifacts in vector graphics and photographs. There is no noticeable deterioration in the quality of characters: the letters look sharp and contrasting.

Although the above embodiment of the invention has been set forth to illustrate, it is clear 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 disclosed in the attached claims.

Claims (8)

1. System for reducing ink consumption when printing through rasterization of fonts, including:
a font rasterizer configured to rasterize a character from a description contained in a font into a bitmap based on current font settings such as a transformation matrix and text effects; at the same time, the character code, font and font parameters are received at the input of the rasterizer; the bitmap is transferred to the fragment repainting module in the background color, and the sizes of the bitmap are transferred to the random number generator;
a module for repainting fragments in the background color, configured to repaint small fragments in the background color in random coordinates of the symbol bitmap in accordance with the claimed method; the module’s input receives the wholesale symbol map from the font rasterizer, random coordinates in the bit map of the symbol from the random number generator, masks M1 and M2, determined by print resolution, parameter N, which sets the degree of ink saving; wherein the fragment repainting module is configured to transmit a request for random coordinates to a random number generator; a bitmap with repainted background fragments is transferred to the font cache;
font cache, configured to perform functions of random access memory for storing bitmaps of characters rasterized for the printed page or the entire print job. 2. The system according to claim 1, characterized in that the module repainting fragments in the background color contains:
a subtracting counter, at the input of which N is supplied at the start of the operation of the module for repainting the fragments in the background color; the counter is clocked by a clock; counter output is switched with a comparator;
a comparator that compares the number coming from the counter with zero; the output of the comparator is connected to the inverter;
the inverter inverts the output signal of the comparator, and this signal is a request for random coordinates (x, y);
random access memory that stores a character bitmap from which you can extract a fragment of a bitmap F1 centered at a point with coordinates (x, y) and size N1 with N2, in which you can replace a fragment of a bitmap F2 centered at a point with coordinates (x , y) and size K1 to K2 to the mask M2, if the signal coming from the mask comparator is equal to a logical unit; the symbol bitmap, M2 mask, random coordinates (x, y) and a signal from the mask comparator are received at the input of the RAM;
a mask comparator that compares the fragment of the bitmap F1 with the center at the point with coordinates (x, y) and size N1 to N2 with the mask M1 and outputs a logical unit if F1 and Ml match; the output of the mask comparator is associated with RAM; a fragment of the bitmap of the symbol F1, mask M1, and random coordinates (x, y) are received at the input of the mask comparator. 3. A method of reducing ink consumption during printing by rasterizing fonts, which consists in performing the following operations:
convert a character from a vector description contained in a font into a bitmap;
generate N pairs of random coordinates (x, y) in the bitmap, where x is the column number, y is the line number;
for each pair of coordinates (x, y), the first fragment of the bitmap F1 is centered at the point with coordinates (x, y) and size N1 by N2 with the first mask M1; and replace the second fragment of the bitmap F2 centered at the coordinates (x, y) and size K1 by K2 with the second mask M2 if F1 and mask M1 match;
save the character bitmap to the font cache. 4. The method according to claim 3, characterized in that in the user-defined font, any part of the printed page, including the entire printed page, is selected as a symbol. 5. The method according to claim 3, characterized in that the size and aperture of the masks M1 and M2 depend on the print resolution and type of printing device. 6. The method according to claim 3, characterized in that the size of the mask M1 is always larger than the size of the mask M2. 7. The method according to claim 3, characterized in that the mask M2 contains a fragment of the background. 8. The method according to claim 3, characterized in that the initial number of the random number generator depends on the size of the symbol bitmap.

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