JPH10202952A - Image-processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent characters from being broken due to a size or a pixel density of characters when image data including characters are to be smoothed, by changing an intensity of a smoothing process in accordance with a character size of an image at a smoothing process part. SOLUTION: Without a smoothing process carried out, a pixel having a density level of an intermediate transfer body 26, 51, 77, 102 is added in (b)-(e). The density level of the pixel (pixel width) to be added to a step part 2 of an image 1 is changed in a plurality of levels, whereby an intensity of the smoothing process is gradually changed. In the case of the image 1 oblique right upward by 45 deg., the intensity of the smoothing process is increased gradually from (b) to (c) to (d) to (e), and therefore an oblique part is less jagged and becomes smooth. In this manner, characters are prevented from being broken due to a size thereof even when image data including characters are subjected to the smoothing process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces multi-value digital image data and adds predetermined pixels to the digital image data, thereby reducing jaggies (jaggies) that occur in an inclined portion of the image. The present invention relates to an image processing apparatus used for performing image processing for performing smoothing and outputting data after the image processing using a laser beam printer or the like.

[0002]

2. Description of the Related Art Conventionally, as a printer which performs image processing on the above digital image data and outputs an image, an electrophotographic apparatus which records an image by irradiating a laser beam on a photosensitive drum in accordance with the image data. Type laser beam printers are widely used. In this laser beam printer, the image is formed by changing the lighting time of the laser beam corresponding to the input bitmap image.
At that time, in order to reduce jaggies (jaggies) that occur in inclined parts such as diagonal lines, curved parts or edge parts of the image,
Image processing is performed using an image processing device.

[0003] Techniques for reducing the above-mentioned jaggies include:
As disclosed in the specification of U.S. Pat. No. 4,437,122, an input bitmap image is divided into 3 × 3 pixels, and the center pixel is converted to a nine-fold pixel density by pattern matching to reduce jaggies. There is a known method for reducing this.

A technique for reducing jaggies by this pattern matching is to input multi-valued digital image data, binarize the multi-valued digital image data,
The central pixel is converted to a nine-fold pixel density by pattern matching, and a predetermined pixel is newly added to the digital image data as shown in FIG. 34, thereby reducing jaggies occurring in the inclined portion of the image. is there. To add a predetermined pixel to this digital image data,
For example, as shown in FIG. 34 (a), the digital image data having a step-like shape inclined at 45 degrees from the lower left to the upper right, as shown in FIG. 34 (b) to (e), By adding pixels of different density levels, such as 26 to 102, at the left end of the image to the inclined portion according to the image data, jaggy generated at the inclined portion of the image is reduced.

Further, by adding a new pixel to the image data as described above, it is possible to prevent an adverse effect caused by uniformly performing a smoothing process for reducing jaggies occurring in an inclined portion of the image on all the images. As a technology,
For example, there is one disclosed in Japanese Patent Application Laid-Open No. 4-189564. That is, Japanese Unexamined Patent Application Publication No.
The output method according to Japanese Patent Application Publication No. 4 (1995) -207 is a method of performing a smoothing process by adding a new supplementary dot to image data. Particularly, when a document in which characters and images are mixed in the same page is output, a character area is output. This is an output method in which whether the character area is smoothed (smoothing ON) and the image area is not smoothed (smoothing OFF) is determined.

[0006]

However, the prior art described above has the following problems. That is, in the case of the output method according to the above-mentioned Japanese Patent Application Laid-Open No. 4-189564, as shown in FIG. 34, a smoothing process is basically performed by adding a supplementary dot to the original image data. In this case, another data is created in a pseudo manner from the image data. for that reason,
In the case of the output method according to the above-mentioned Japanese Patent Application Laid-Open No. 4-189564, when a smoothing process is performed even for a character area,
As the number of dots at the character boundary increases, the line representing the character tends to become thicker. In this case, a large character, for example, 4
For smoothing processing on characters above the point (pt), even if the characters are slightly thick, it is unlikely to cause any problem, but conversely, small characters, for example, characters less than 4 pt,
In addition, if a character having a relatively high pixel density, for example, a character having a large number of strokes, for example, a kanji character having six strokes or more or a character having a font style of Gothic is subjected to the same smoothing processing, the character is likely to be broken. There was a problem.
In addition, such a problem of character collapse tends to occur more easily in a character having a pixel density higher than or equal to the size of the character.

The above problems will be described more specifically.
FIG. 35 is an example of enlarging a part of the kanji kanji “line”, and FIG. 35 shows the part of the kanji “harai” that is closest. In such a case, the pixel 200 having the density level “102” shown in FIG.
When a new smoothing process is performed on the lower and upper inclined portions in the above, the shortest distance L1 at which the output images are closest to each other is reduced, and the shortest distance L between the output images during development is reduced.
There is a problem that the toner is buried in one space (character collapse). In such a case,
Kanji: where the pixel portion of the "Harai" of the line is closest, the smaller the size of the character "Line", the smaller the gap between pixels, the more likely it is to occur. In other words, there are more places to approach,
There is a problem that the number of crushed portions between lines representing characters increases, and the characters themselves are easily crushed. Furthermore, not only the character "line" but also small characters and characters having a high image density are more likely to occur as the image density increases, that is, the number of places approaching increases as described above. As a result, the number of crushed portions between lines representing characters increases, and the characters themselves are easily crushed.

Therefore, in order to solve such a problem (character collapse) of the prior art, a method of not performing a smoothing process on a character smaller than a predetermined size (for example, 4 pt) is considered. However, in this case, there is a difference in the result of outputting the image at a predetermined size (for example, 4 pt), and the difference in the output result of this image is conspicuous, giving a new problem that a sense of incongruity is given. Occurs.

[0009] To solve the above problems,
For a character smaller than a predetermined size (for example, 4 pt), a technique of deforming the character (font data) itself (decimating dots on a bitmap) has already been proposed. For example, 4pt)
There is a difference in the output result of the image at the boundary, and the difference in the output result of this image is conspicuous, giving rise to a new problem of giving a sense of incongruity.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the prior art, and has as its object to reduce the size of a character even when image data including the character is subjected to a smoothing process. Alternatively, it is possible to prevent the occurrence of character collapse depending on the pixel density, and to give a sense of incongruity at the change point as in the case where the presence or absence of font data or smoothing processing is switched at a predetermined character size or the like. It is an object of the present invention to provide an image processing apparatus that does not have any problem.

[0011]

That is, according to the first aspect of the present invention, there is provided an image pattern judging section for judging an arrangement of pixels of input image data, and an image pattern judging section based on a judgment result by the image pattern judging section. In an image processing apparatus having a smoothing processing unit for performing a smoothing process by adding a predetermined pixel to a concave portion at an edge portion of an image, the intensity of the smoothing process is changed according to the character size of the image. ing.

According to a second aspect of the present invention, there is provided an image pattern judging section for judging the arrangement of pixels of input image data, and an edge portion of the image based on a judgment result by the image pattern judging section. In an image processing apparatus having a smoothing processing unit for performing a smoothing process by adding a predetermined pixel to a concave portion, the intensity of the smoothing process is changed according to the pixel density of an image.

Further, according to a third aspect of the present invention, there is provided an image pattern judging section for judging an arrangement of pixels of input image data, and an edge portion of the image based on a judgment result by the image pattern judging section. In an image processing apparatus having a smoothing processing unit for performing a smoothing process by adding a predetermined pixel to a concave portion, the intensity of the smoothing process is changed according to the character size and the pixel density of the image.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings.

FIG. 1 is a schematic diagram showing a basic method of smoothing processing in an image processing apparatus according to an embodiment of the present invention.

FIG. 1 shows an example of a diagonally shaded image 1 of 45 degrees rising to the right, and by changing the density level (pixel width) of the pixel 3 added to the diagonally stepped portion 2 over a plurality of stages.
It is the figure which showed the mode that the intensity | strength (the degree of smoothness of the shaded area jaggy) of a smoothing process changed gradually. FIG.
In (a) to (e), all the pixels 3 to be added are commonly added near the step (rightward). FIG. 1 (a)
FIG. 1B shows a case where the smoothing process is not performed.
(E) shows a case where pixels having density levels of 26, 51, 77, and 102 (pixel density levels range from 0 to 255) are added. FIG. 1 (a)
In (e), a rectangular hatched portion in the figure represents the laser drive signal after pulse width modulation, and a vertical elliptical portion in the rectangle given the symbol b applies the present invention. The laser beam beam spot of the laser beam applied to the photosensitive drum of the laser beam printer, the curved portion with the reference character c is the output image actually recorded on the recording paper,
Each is schematically shown. FIG. 1 (a)-
As can be seen from (e), the intensity of the smoothing process is gradually changed by changing the density level (pixel width) of the pixel added to the step portion 2 of the image 1 in a plurality of steps. Further, in the case of the image 1 having a 45-degree right-upward oblique line shown in FIG. 1, the intensity of the smoothing process gradually increases as shown in FIGS. 1B, 1C, 1D, and 1E. It can be seen that the degree of jaggy smoothness in the part increases. If the density level (pixel width) of the pixel to be added is further increased from that shown in FIG. 1E, the step portion 2 is rather thickened, and conversely, the intensity of the smoothing process is reduced.

As the pixel 3 added to the image 1 for performing the smoothing process, for example, in the case of the image 1 having an oblique line rising 45 degrees to the right, the density level (pixel width) is “10”.
The pixel 3 of 2 ″ is used, but in the case of another image 1,
Pixels 3 having an appropriately determined density level are added to the step portion 2 and the like.

FIG. 2 is a block diagram showing a color laser beam printer to which the image processing apparatus according to the present invention can be applied. Here, the image processing apparatus according to the present invention can be applied not only to a color laser beam printer but also to a monochrome laser beam printer.

In FIG. 2, reference numeral 21 denotes a photosensitive drum as an image bearing member.
Is driven to rotate at a predetermined rotational speed along a direction of an arrow by a driving unit (not shown). Around the photosensitive drum 21, a scorotron charger 22 for uniformly charging the surface of the photosensitive drum 21, a laser optical system 23, and respective developers of yellow, magenta, cyan, and black were accommodated. Four color developing devices 24a, 24b, 24c, 24d and a transfer charger 25
And an intermediate transfer belt 26 for transferring and holding the toner images of the respective colors sequentially formed on the photosensitive drum 21 in a state of being superimposed on each other, are sequentially arranged along the rotation direction of the photosensitive drum 21. . Around the intermediate transfer belt 26, the toner images of a predetermined number of colors superimposed on the intermediate transfer belt 26 are conveyed to a position corresponding to the intermediate transfer belt 26 at a predetermined timing. Transfer roll 27 for collectively transferring onto the recording paper 20 to be transferred, and a transport belt for transporting the recording paper 20 as a recording medium on which the toner image of a predetermined number of colors has been transferred to a fixing device 29 described below. 28 and the conveyor belt 2
And a fixing device 29 for fixing the toner image on the recording paper 20 conveyed by the fixing device 8.

The scorotron charger 22 for uniformly charging the surface of the photosensitive drum 21 has two or more discharge wires so as to stably and uniformly charge the second and subsequent colors of an image. It is desirable to use the scorotron charger used.

The color developing units 24a, 24b,
As the components 24c and 24d, for example, a two-component developing device having a known configuration can be used. In particular, the tips of the ears of the two-component developer composed of the toner and the carrier are formed on the surface of the photosensitive drum 21 and the second color. Subsequent photosensitive drum 21
In order to avoid contact with the toner image formed thereon, a two-component developer supported on a developing roll is arranged such that the ears of the two-component developer face the surface of the photosensitive drum 21 via a gap. Further, each of the color developing units 24a,
As a developing bias applied to 4b, 24c and 24d, a DC voltage (DC + AC voltage) on which an AC voltage is superimposed so as not to disturb the toner image formed on the photosensitive drum 21 and to obtain a desired high image quality. ) Is desirably set, for example, in which the AC component of the developing bias is adjusted.

FIG. 3 is a schematic diagram showing a laser optical system used in the laser beam printer shown in FIG.

The laser optical system 23 includes a semiconductor laser 31 driven by a laser drive circuit described later, a collimator lens 32, a polygon mirror 33, and an fθ lens 34. The semiconductor laser 31 is modulated by a laser drive circuit described later to perform an on / off operation, and emits a laser beam 35 modulated by a so-called pulse width modulation method. The laser beam 35 emitted from the semiconductor laser 31 is applied to the surface of the polygon mirror 33 via the collimator lens 32, is reflected and deflected by the surface of the polygon mirror 33 rotating at high speed, and passes through the fθ lens 34. The photosensitive drum 21 is scanned and exposed along the main scanning direction (axial direction of the photosensitive drum 21).

In the laser beam printer configured as described above, as shown in FIG. 2, after the surface of the photosensitive drum 21 is uniformly charged to a predetermined potential by the scorotron charger 22, the photosensitive drum 21 The surface corresponding to the first color is scanned and exposed by the laser optical system 23 to form an electrostatic latent image. The first-color electrostatic latent image formed on the photosensitive drum 21 is developed by a first-color developing device, for example, a yellow color developing device 24a, to become a toner image. The first color yellow toner image is electrostatically transferred onto the intermediate transfer belt 26 by the charging of the transfer charger 25 at the transfer position. Thereafter, the photosensitive drum 21 on which the toner image of the first color has been transferred onto the intermediate transfer belt 26 is cleaned by a cleaning unit (not shown), and the charging, exposure, and development steps are performed again by a predetermined number of colors in the same manner as described above. The toner images of four colors of yellow, magenta, cyan, and black sequentially formed on the photosensitive drum 21 are sequentially transferred onto the intermediate transfer belt 26 in a state of being superimposed on each other. The four-color toner images transferred onto the intermediate transfer belt 26 are transferred to the intermediate transfer belt 26 at a predetermined timing.
After being transferred onto the recording paper 20 at once by the transfer roll 27 contacting the recording paper 20 via the recording paper 20,
The recording paper 20 is transported by the transport belt 28 to the fixing device 2.
9 is conveyed. The four color toner images are melted and mixed by heat and pressure by the fixing device 29 and fixed on the recording paper 20, and the recording paper 20 is discharged out of the apparatus, thereby completing the color image forming process.

Further, on the surface of the photoreceptor drum 21 after the transfer process of the toner image of each color is completed, the charge of the residual toner is erased by a static eliminator (not shown), and the residual toner and the like are removed by a cleaning device having a blade. After that, the residual charges are further erased by the discharging lamp, and the apparatus is prepared for the next color image forming step.

In this embodiment, an apparatus for forming a full-color image using the intermediate transfer belt 26 has been described as a laser beam printer. However, the present invention is not limited to this. A full-color image is formed by sequentially transferring a toner image of each color to be formed on a recording sheet or an intermediate transfer medium held on an intermediate transfer drum, or a plurality of photosensitive drums, A so-called tandem-type color image forming apparatus that forms a full-color image by sequentially transferring a plurality of toner images formed by a drum onto a recording sheet that is sequentially transported to a transfer position of each photosensitive drum; Of course, it is also good. Further, as described above, the laser beam printer may be a black-and-white laser beam printer.

FIG. 4 is a block diagram showing an image processing apparatus according to an embodiment of the present invention applied to the laser beam printer.

As the image data recorded by the laser beam printer, for example, image data of 256 gradations of 8 bits from 0 to 255, which are quantized so that the density increases as the value increases. . That is, in the case of monochrome image data, “0” represents “white” and “25”
"5" means "black". In the case of color image data, for example, “red (R), red (R), green (green)”,
"Magenta (M), Cyan (C), Yellow (Y)",
Generally, one image data is represented by a plurality of components such as "brightness (L ^* ), hue (H ^* ), saturation (C ^* )" or "L ^* a ^* b ^* ". In this case, For example, the following embodiment may be similarly applied to each component represented by 8-bit 256 gradations from 0 to 255.

In FIG. 4, the input multi-valued image data is input to an edge detection unit 40 and a binarization unit 41, and the binarization unit 41 binarizes the multi-valued data. Input to the section 42. In the edge detection unit 40,
The presence / absence and direction of the edge of the input multi-valued image data are detected, and an edge direction flag is added to the image data and output. In addition, the pattern matching unit 42 performs “binary → multi-value conversion” to reduce jaggies of the binary data, and further generates a flag indicating the edge direction. The combining unit 43 combines the outputs of the edge detecting unit 40 and the pattern matching unit 42 and outputs the image data and the edge direction Bragg to the waveform control screen unit 44. The waveform control screen unit 44 generates an “on / off” signal of the laser beam from the input image data and the edge direction flag.

FIG. 5 shows the internal configuration of the edge detector. Each of the one-line memories 45 and 46 is a memory capable of storing one line of image data, and performs a blocking process for performing a spatial filtering process on the input image data. The 3 × 3 filter unit 47
A filtering process is performed on the blocked image data to detect an edge direction of the image data and output an edge direction flag of 2 bits. The delay unit 48 synchronizes the input image data with the edge direction flag output from the 3 × 3 filter unit 47. In the edge signal adding unit 49, the image signal 8 bits output from the delay unit 48 and the 3 × 3 filter unit 47
Are combined and output as a 10-bit signal. As shown in FIG. 6, the output signal of the edge signal adding section 49 is the upper 2
The bit is a flag indicating the edge direction, and the lower 8 bits are an image signal.

Next, the 3 × 3 filter section 47 will be described in more detail with reference to FIG. The input image data is divided into nine (3 × 3) pixels around the target pixel. This block image 50 has four coefficients 5
The convolution operation is performed using 1, 52, 53, and 54, and each operation result has four types of edge signals EG-1, EG.
-2, EG-3, EG-4. Maximum edge detector 5
5, four types of edge signals EG-1, EG-2, EG
-3 and EG-4 are obtained, the largest one of the four absolute values is output to the edge canceling unit 56, and the edge signal number (1,
2, 3, 4) to the edge direction flag generation unit 57
Output to The edge direction flag generation unit 57 includes a maximum edge number output from the maximum edge detection unit 55 and four types of edge signals EG-1, EG-2, EG-3, and EG-.
4 has been entered. One of the four types of edge signals EG-1, EG-2, EG-3 and EG-4 is selected by the maximum edge number, and the edge direction is determined by the sign (positive or negative) of the selected edge signal. Is determined, and a 2-bit edge direction flag is generated. For example, when the maximum edge number is “2” and the value of EG-2 is “positive”, the edge direction of the target pixel is “left”. Here, a case where the density decreases from top to bottom as shown in FIG. 8A is an “upper edge”, and a case where the density decreases from left to right as shown in FIG. 8B. Let's say "left edge". As shown in FIG. 9, “00” means no edge, “01” means upper or lower edge, “10” means right edge, and “11” means left edge.

As described above, the edge direction flag generator 5
At 7, the edge direction flag “01” is set for all pixels.
Either “10” or “11” is generated. In the edge canceling section 56, when the maximum edge absolute value output from the maximum edge detecting section 55 is equal to or smaller than a certain value, the edge direction flag is reset to “00”.

FIG. 10 is a diagram for explaining the internal configuration of the pattern matching unit 42. As shown in FIG. 11, the binarization unit 41 outputs “1” when the input image data is “255”, and outputs “0” when the input image data is “less than 255”. 1 generated by the binarization unit 41
The bit signal is divided into blocks by using the one-line memories 60 and 61, and is input to the 3 × 3 pattern matching unit 62.

FIG. 12 shows a 3 × 3 pattern matching unit 6.
2 is a diagram for explaining in more detail the 1-line memory 6
The data of each of the 9 pixels that are divided into 3 × 3 blocks around the pixel of interest using 0 and 61 are stored in the lookup table R.
It is connected to the address of OM63. In the look-up table, if the value of the pixel of interest “e” is “0” except for the patterns shown in FIGS. 13 and 14, the image data “0” and the edge direction flag “00” are set to the pixel of interest. If the value of “e” is “1”, the image data “255”
The output of the edge direction flag “00” is set, and in the case of the patterns shown in FIGS. 13 and 14, the image data and the edge direction flag shown in each table are output. It is output as 10-bit data in the format shown.

The pattern matching section 62 determines “25” from the continuity of the density value of “255” in the multi-valued image data.
When pixels having a density of "5" are continuous in an oblique direction, there is an effect of reducing jaggy there.

FIG. 15 shows the internal configuration of the synthesizing section 43. The synthesizing unit 43 is a unit for synthesizing the outputs of the edge detecting unit 40 and the pattern matching unit 42.
When the image data input from the pattern matching unit 42 to the synthesis unit 43 is “0” or “255”, the image data and the edge direction flag input from the edge detection unit 40 are output from the synthesis unit. The image data input from the pattern matching unit 42 to the synthesizing unit 43 is “0”.
, And other than “255”, the image data and the edge direction flag input from the pattern matching unit 42 are output from the synthesizing unit 43. As described above, in the synthesizing unit 43, when data other than “0” or “255” is output by the pattern matching unit 42, that is, pixels of “255” density in the multi-valued image data are continuously continuous in the oblique direction. In this case, the pixel value generated to reduce the diagonal jaggy is preferentially output.

In the waveform control screen unit 44, as shown in FIG. 16, the 8-bit multi-valued image data input from the synthesizing unit 43 is converted into an analog value via a D / A converter 71, and the selector is selected by an edge direction flag. The triangular wave selected at 72 is compared with the comparator 73 to generate a laser control signal.

Here, as shown in FIG. 17, the waveform of the triangular wave selected by the selector 72 has a period twice as long as the pixel clock, and is the same as the triangular wave A and the triangular wave B, which are 180 degrees out of phase, and the pixel clock. This is a triangular wave C having a period. FIG. 18 shows the relationship between the edge direction flag and the selected triangular wave.

Here, an explanation will be given using an example. When the image data and the edge direction flag are input to the waveform control screen as shown in FIG. 19, the triangular wave shown at the bottom of FIG. 19 is selected. FIG. 20 schematically shows a laser control signal generated by the triangular wave selected in this way. Here, it is assumed that the laser beam printer of this embodiment is a so-called image writing type printer in which toner adheres to a location where a laser beam is irradiated on a photosensitive drum and a black image is output on paper. Here, FIG. 21 shows a case where a laser control signal is generated using a triangular wave C having the same cycle as the pixel clock without controlling the waveform of the image data shown in FIG. 21 is compared with FIG. 20, the laser control signal is more concentrated in the center in FIG. 18, which performs waveform generation, whereas in FIG. 20, the laser-on signal is divided into three. 20 can generate a clearer electronic latent image on the photoreceptor. Further, as shown in FIG. 18, the triangular wave C having the same cycle as the pixel clock is selected only when the vertical edge direction flag is input in synchronization with the image signal. That is, when the edge direction flag is “00”, the triangular wave A having a cycle twice as long as the cycle of the pixel clock is selected. This is, for example, 200 lpi in a printer capable of printing at a pixel density of 400 dpi (dot / inch).
An output image will be generated using a (line / inch) universal screen. The reason for this is that, when a highlight portion having a low density is output, a laser control signal is generated using a triangular wave having the same cycle as the pixel clock as shown in FIGS. (See FIG. 22A)
When the laser irradiation time is very short, it is difficult to stably form a latent image electronically on the photoconductor, and as a result, the image data This is because it is difficult to output the gradation accurately.

As described above, the jaggy reduction method in the case where pixels having a density value of "255" in a multi-valued document continue in an oblique direction has been described. When embedding character data in normal multi-valued image data (for example, a photograph), character data is described at the maximum density in most cases. This is a very effective means for improving image quality.

Incidentally, the image processing apparatus according to this embodiment is configured to change the intensity of the smoothing processing in accordance with the character size.

That is, as shown in FIG. 10, apart from the multi-valued input image data, the pattern matching unit 42
A character size signal synchronized with the multi-value input image data is input. As the character size signal, a signal indicating the size of a character normally included in font data representing the character is used. In this case, as shown in FIG. A signal represented by two bits is used. The signal indicating the character size is input to the multiplication coefficient generation unit 81 via the one-line memory 80, and the output signal of the multiplication coefficient generation unit 81 is input to the multiplier 82. In this multiplier, 3
The 8-bit image data output from the × 3 pattern matching section 62 is multiplied by a multiplication coefficient a output from the multiplication coefficient generation section 81.

FIG. 13 is a diagram showing the contents of the LUT of the 3 × 3 pattern matching section 62 in FIG. The pixel of interest is
The pixel at the center of the input pattern (3 × 3 center: thick frame). FIG. 24 is a diagram showing the inside of the multiplication coefficient generator of FIG.

By adopting such a configuration, FIG.
The final multi-valued output image data value is determined by multiplying the image data output from the 3 × 3 pattern matching unit 62 by a coefficient a determined by the character size signal in a multiplier 81. Can be.

In the image processing apparatus according to the present embodiment, even if the image data including the character is subjected to the smoothing processing as described below, the character collapse may occur depending on the size of the character. It is possible to prevent the user from feeling uncomfortable at the change point, as in the case where the presence or absence of the font data or the smoothing process is switched at a predetermined character size or the like.

That is, in the above image processing apparatus, FIG.
As shown in (3), when the 3 × 3 pattern matching unit 62 performs the smoothing process on the multi-valued image data,
By multiplying the image data output from the × 3 pattern matching unit 62 with a coefficient a determined by the character size signal by the multiplier 82, the final value of the multi-value output image data can be determined. It has become.

Therefore, for example, when recording the character of "line" as shown in FIG. 25, as shown in FIG. 26, at the portion where the "harai" portion of the hair is closest, as shown in FIG. As shown in FIG. 24, the output of the 3 × 3 pattern matching unit 62 is multiplied by a predetermined multiplication coefficient a in accordance with the size of the character, thereby changing the intensity of the smoothing process in a plurality of stages. Since the multiplication coefficient a becomes smaller as the character becomes smaller, the strength of the smoothing process becomes weaker. Therefore, even if the characters become smaller, the intensity of the smoothing process becomes weaker, as shown in FIG. 26B, so that the density level of the pixel added to the 45-degree hatched concave portion becomes 51, for example. It can be seen that the value of the shortest distance L2 between the output images is larger than the value of L1, and therefore, it is difficult for the characters to collapse.

As described above, in the above embodiment, by changing the intensity of the smoothing process in a plurality of stages according to the character size, even if the smoothing process is performed on the image data including the character, the smoothing process is performed in accordance with the size of the character. It is possible to prevent the occurrence of character collapse, and it is also possible to prevent the user from feeling uncomfortable at the changing point, such as when switching between font data and the presence or absence of smoothing processing at a predetermined character size or the like. It has become.

Second Embodiment FIG. 27 shows a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and described. , The intensity of the smoothing process is changed not according to the character size but according to the pixel density.

That is, in the image processing apparatus according to the second embodiment, as shown in FIG. 27, the pattern matching section 42 stores the pixel density synchronized with the multi-level input image data separately from the multi-level input image data. Signal is input. As the pixel density signal, a signal indicating a value corresponding to the pixel density for each character is used by referring to a table or the like (not shown) based on data representing a character size, a font, and the like. As shown in FIG. 28, a signal represented by 2 bits according to the pixel density is used. The signal indicating the pixel density is supplied to the one-line memory 8.
0, is input to the multiplication coefficient generation unit 81, and the output signal of the multiplication coefficient generation unit 81 is
Has been entered. In this multiplier, 8-bit image data output from the 3 × 3 pattern matching section 62 is multiplied by a multiplication coefficient b output from the multiplication coefficient generation section 81. FIG. 29 is a diagram showing the inside of the multiplication coefficient generating unit of FIG.

By adopting such a configuration, FIG.
By multiplying the image data output from the 3 × 3 pattern matching unit 62 with a coefficient b determined by the pixel density signal by the multiplier 81, the final value of the multi-value output image data can be determined. .

As described above, in the above-described embodiment, by changing the intensity of the smoothing process in a plurality of stages in accordance with the pixel density, even if the smoothing process is performed on the image data including the character, the character can be changed depending on the pixel density. Can be prevented from occurring, and it is possible to prevent the user from feeling uncomfortable at the changing point as in the case where the presence or absence of the font data or the smoothing process is switched at a predetermined character size or the like. Has become.

Further, in this embodiment, since the intensity of the smoothing process is changed in a plurality of steps according to the pixel density, compared with the case where the intensity of the smoothing process is changed in a plurality of stages according to the size of the character, Even when a large character has a high pixel density, that is, when recording a character having a large number of strokes, the intensity of the smoothing process can be changed in a plurality of stages, which is more effective in preventing character collapse.

Other configurations and operations are the same as those of the above-described embodiment, and the description thereof will be omitted.

Third Embodiment FIG. 30 shows a third embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and described. , The intensity of the smoothing process is changed according to both the character size and the pixel density.

That is, in the image processing apparatus according to the third embodiment, as shown in FIG. 30, the pattern matching section 42 stores the character size synchronized with the multi-valued input image data separately from the multi-valued input image data. And a signal indicating the pixel density. The signals indicating the character size and the pixel density include a signal indicating the character size normally included in font data indicating the character and a table (not shown) based on the data indicating the character size and font. For example, a signal indicating a value corresponding to the pixel density is used for each character by referring to the table. In this case, as shown in FIG. 31, the signal is displayed in 2 bits according to the size of the character and the pixel density. A signal is used. The signal indicating the character size and the signal indicating the pixel density are stored in a one-line memory 9.
The signals are input to the multiplication coefficient generators 92 and 93 via 0 and 91, and the output signals of the multiplication coefficient generators 92 and 93 are input to the multiplier 94. This multiplier 94
In this case, the multiplication coefficient generation units 92 and 9 are applied to the 8-bit image data output from the 3 × 3 pattern matching unit 62.
The multiplication coefficients a and b output from 3 are multiplied. FIG. 32 is a diagram showing the inside of the multiplication coefficient generating units 92 and 93 of FIG.

By adopting such a configuration, FIG.
Is multiplied by a multiplier 94 with the image data output from the 3 × 3 pattern matching unit 62 by the coefficients a and b determined by the signal indicating the character size and the pixel density signal. The value of the image data can be determined.

As described above, in the above embodiment, by changing the intensity of the smoothing process in a plurality of stages in accordance with the size of the character and the pixel density, even if the image data including the character is subjected to the smoothing process, It is possible to prevent the occurrence of character collapse depending on the size and pixel density, and at the point of change, such as when switching between font data and smoothing processing at a predetermined character size, etc. Can be prevented from being given.

Further, in this embodiment, since the intensity of the smoothing process is changed in accordance with both the character size and the pixel density, the smoothing process considering both the character size and the pixel density is performed. This can further prevent the occurrence of character collapse, and can record an image having a high resolution and subjected to a smoothing process.

Other structures and operations are the same as those of the above-described embodiment, and the description thereof will be omitted.

In the configuration of FIG. 30 described in the above embodiment, a multiplication coefficient generation section A and a multiplication coefficient generation section B are provided separately from the LUT of the 3 × 3 pattern matching section.
By multiplying the pixel data, which is the LUT output of the pattern matching unit, by a coefficient a determined by the character size signal and a coefficient b determined by the pixel density signal by a multiplier, the final value of the multi-valued output image data is obtained. Although the configuration is determined, as shown in FIG. 33, the LUT of the 3 × 3 pattern matching unit, the multiplication coefficient generation unit A, and the multiplication coefficient generation unit B can be collectively formed as one LUT. However, in this case, it is necessary to set in advance the final multi-valued output image data value after the multiplication result in the image data to be output from the LUT. Further, although the LUT is described as ROM, it is also possible to use a RAM configuration.

[0062]

The present invention has the above-described structure and operation. Even when image data including a character is subjected to a smoothing process, it is possible to prevent occurrence of character collapse depending on the character size or pixel density. It is possible to provide an image processing apparatus which can prevent such a situation and does not give a sense of incongruity at the changing point as in the case where the presence or absence of the font data or the smoothing processing is switched at a predetermined character size or the like.

[Brief description of the drawings]

FIGS. 1A to 1E are schematic views showing an embodiment of an image processing apparatus according to the present invention. FIG.

FIG. 2 is a configuration diagram showing a color image forming apparatus to which the image processing apparatus according to the present invention can be applied.

FIG. 3 is a configuration diagram illustrating a ROS of the image forming apparatus of the same color.

FIG. 4 is a block diagram showing an embodiment of an image processing apparatus according to the present invention.

FIG. 5 is a block diagram illustrating an edge detection unit.

FIG. 6 is a schematic diagram showing image data.

FIG. 7 is a block diagram illustrating an edge direction flag generation unit.

FIGS. 8A and 8B are explanatory diagrams showing an edge detection method, respectively.

FIG. 9 is an explanatory diagram showing an edge direction flag.

FIG. 10 is an explanatory diagram showing a pattern matching unit.

FIG. 11 is a block diagram illustrating a binarizing unit.

FIG. 12 is an explanatory diagram showing a pattern matching unit.

FIG. 13 is an explanatory diagram illustrating a detection state of a pattern matching unit.

FIG. 14 is an explanatory diagram illustrating a detection state of a pattern matching unit.

FIG. 15 is a block diagram illustrating a data synthesis unit.

FIG. 16 is a block diagram illustrating a laser control signal generation unit.

FIG. 17 is a waveform diagram showing a laser control signal.

FIG. 18 is a table showing types of triangular waves.

FIG. 19 is a chart showing the types of selected triangular waves.

FIG. 20 is a waveform diagram showing a laser control signal.

FIG. 21 is a waveform diagram showing a laser control signal.

FIG. 22 is a waveform diagram showing a laser control signal.

FIG. 23 is a chart showing character size signals.

FIG. 24 is a table showing multiplication coefficients.

FIGS. 25A and 25B are schematic diagrams showing examples of characters.

FIGS. 26A and 26B are schematic diagrams showing examples of characters.

FIG. 27 is a block diagram showing another embodiment of the image processing apparatus according to the present invention.

FIG. 28 is a chart showing an image density signal.

FIG. 29 is a chart showing multiplication coefficients.

FIG. 30 is a block diagram showing another embodiment of the image processing apparatus according to the present invention.

FIGS. 31A and 31B are tables showing a character size signal and an image density signal, respectively.

FIGS. 32A and 32B are tables showing the multiplication coefficients of the multiplication coefficient generators A and B, respectively.

FIG. 33 is a block diagram showing another embodiment of the image processing apparatus according to the present invention.

FIGS. 34A to 34E are schematic diagrams each showing an operation of the image processing apparatus.

FIGS. 35A and 35B are schematic diagrams showing examples of characters.

[Explanation of symbols]

40 edge detection unit, 41 binarization unit, 42 pattern matching unit, 43 synthesis unit, 44 waveform control screen unit.

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[Procedure amendment]

[Submission date] April 30, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG. 3

FIG. 4

FIG.

FIG. 2

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FIG. 6

FIG. 8

FIG. 9

FIG. 11

FIG.

FIG.

FIG. 23

FIG. 28

FIG. 7

FIG. 13

FIG. 14

FIG.

FIG.

FIG. 10

FIG. 27

FIG.

FIG. 16

FIG.

FIG. 21

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FIG. 24

FIG. 25

FIG. 26

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FIG.

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FIG. 35

Claims (3)

[Claims] An image pattern determining unit that determines an arrangement of pixels of input image data, and a predetermined pixel is added to a concave portion at an edge of an image based on a result of the determination by the image pattern determining unit. An image processing apparatus having a smoothing processing unit for performing a smoothing processing, wherein the intensity of the smoothing processing is changed according to the character size of the image. 2. An image pattern determining unit for determining an arrangement of pixels of input image data, and a predetermined pixel is added to a concave portion at an edge of an image based on a determination result by the image pattern determining unit. And a smoothing processing unit for performing a smoothing process, wherein the intensity of the smoothing process is changed according to the pixel density of the image. 3. An image pattern determining unit for determining an arrangement of pixels of input image data, and a predetermined pixel is added to a concave portion at an edge of an image based on a determination result by the image pattern determining unit. An image processing apparatus having a smoothing processing unit for performing a smoothing processing, wherein an intensity of the smoothing processing is changed according to a character size and a pixel density of an image.