JP3861352B2 - Image processing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention performs image processing for reducing (smoothing) jaggies (jagged edges) generated in an inclined portion of an image by inputting multi-value digital image data and newly adding predetermined pixels to the digital image data. The present invention relates to an image processing apparatus used for outputting data after image processing using a laser beam printer or the like.
[0002]
[Prior art]
Conventionally, as a printer that performs image processing on the digital image data and outputs an image, an electrophotographic laser beam printer that records an image by irradiating a photoconductive drum with a laser beam according to the image data Is widely spread. In this laser beam printer, an image is formed by changing the lighting time of the laser beam in accordance with the input bitmap image. At this time, jaggies (jagged edges) generated in a slanted portion of the image, a curved portion or an edge portion, etc. ) Is reduced by using an image processing apparatus.
[0003]
As a technique for reducing the jaggy, as disclosed in the specification of US Pat. No. 4,437,122, the input bitmap image is blocked into 3 × 3 pixels, and the center pixel is multiplied by 9 times by pattern matching. There is known a method of reducing the jaggy by converting the pixel density to the above.
[0004]
The technology to reduce jaggy by this pattern matching is to input multi-value digital image data, binarize this multi-value digital image data, and then convert the central pixel to 9 times the pixel density by pattern matching. As shown in FIG. 34, jaggies generated in the inclined portion of the image are reduced by newly adding predetermined pixels to the digital image data. When a predetermined pixel is newly added to the digital image data, for example, as shown in FIG. 34A, a stepped digital image data inclined 45 degrees from the lower left to the upper right is shown. As shown in 34 (b) to (e), an image is obtained by adding pixels of different density levels according to image data, such as 26 to 102, to the left end of the digital image data in the inclined portion. The jaggy generated in the slanted portion is reduced.
[0005]
In addition, as described above, as a technique for preventing adverse effects caused by uniformly applying smoothing processing to all images to reduce jaggies generated in the inclined portion of the image by adding new pixels to the image data as described above. For example, there is one disclosed in JP-A-4-189564. That is, the output method according to Japanese Patent Application Laid-Open No. 4-189564 is a method for performing smoothing processing by newly adding supplemental dots to image data, and in particular, a document in which characters and images are mixed in the same page. An output method for identifying whether a character area or an image area is to be output, and performing a process that applies smoothing to the character area (smoothing ON) and does not apply smoothing to the image area (smoothing OFF). is there.
[0006]
[Problems to be solved by the invention]
However, the conventional technique has the following problems. That is, in the case of the output method according to Japanese Patent Laid-Open No. 4-189564, a smoothing process is basically performed by adding supplemental dots to the original image data as shown in FIG. This creates pseudo-different data from the image data. For this reason, in the case of the output method according to the above Japanese Patent Laid-Open No. 4-189564, when the smoothing process is performed even in the character area, the number of dots at the character boundary portion increases, and the line representing the character tends to become thicker. . In this case, it is difficult to cause a problem even if the characters are slightly thicker as long as the smoothing process is performed on a large character, for example, a character of 4 points (pt) or more, but conversely a small character, for example, less than 4 pt. Characters that are relatively high in pixel density, for example, characters with a large number of strokes, such as Kanji characters that are characters with 6 or more strokes, and characters that have Gothic fonts are also subject to crushing. There was a problem of becoming. In addition, such a problem that the characters are crushed tends to occur more easily as the character density is higher than the character size.
[0007]
To explain the above problem more specifically, FIG. 35 shows an example of an enlarged part of the Chinese character “line”: FIG. 35 shows the “Harai” part of the kite closest. It shows what you did. In such a case, a smoothing process is newly performed in which the pixel 200 having the density level “102” shown in FIG. 35E is newly added to the lower and upper inclined portions of the upwardly inclined portions 201 and 202 of the character. When applied, the shortest distance L1 that is closest to the output images becomes small, and there is a problem that toner is buried between the shortest distances L1 between the output images during development (character collapse). Also, in such a case, the pixel part of “Karai” that is the kanji character: the edge of the line is closest, the smaller the size of the character “line”, the smaller the gap between the pixels. As a result, the number of parts that approach each other increases, and the number of parts that are crushed between the lines representing the characters increases, which causes the problem that the characters themselves are easily crushed. Furthermore, not only the characters “line” but also small characters and characters with high image density, the higher the image density, the more likely it is to occur. As a result, the number of crushed portions between the lines representing the characters increases and the characters themselves are easily crushed.
[0008]
Therefore, in order to solve such a problem of the conventional technology (character collapse), a method of preventing the smoothing process from being applied to characters smaller than a certain size (for example, 4 pt) is considered. However, in this case, a difference occurs in the result of outputting the image with a predetermined size (for example, 4 pt) as a boundary, and the difference in the output result of this image becomes conspicuous, giving a new problem of giving a sense of incongruity. Arise.
[0009]
Further, in order to solve the above-mentioned problem, (2) for a character smaller than a certain predetermined size (for example, 4 pt), the character (font data) itself is deformed (dots are thinned out on the bitmap). However, in this case as well, there is a difference in the result of outputting an image with a predetermined size (for example, 4 pt) as a boundary, and the difference in the output result of this image is noticeable, giving a sense of incongruity. A new problem arises.
[0010]
Therefore, the present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to achieve character size or pixel density even when smoothing processing is performed on image data including characters. Therefore, it is possible to prevent the occurrence of character crushing, and it does not give a sense of incongruity at the change point as when the font data or smoothing processing is switched at a predetermined character size or the like. An object is to provide an image processing apparatus.
[0011]
[Means for Solving the Problems]
That is, the invention described in claim 1 is input. Multi-value image data An image pattern determination unit that determines the arrangement of the pixels, and a smoothing processing unit that performs a smoothing process by adding a predetermined pixel to the concave portion of the edge portion of the image based on the determination result by the image pattern determination unit. In an image processing apparatus having The image pattern determining unit determines an array of pixels of the input multi-value image data, and the smoothing processing unit is configured to input the input multi-value image data and the pixels determined by the image pattern determining unit. A plurality of levels of smoothing processing strength applied according to the array and the character size of the image, the input multi-value image data, the pixel array determined by the image pattern determination unit, The intensity of the smoothing process is changed according to the character size of the image.
[0012]
Further, the invention described in claim 2 is inputted. Multi-value image data An image pattern determination unit that determines the arrangement of the pixels, and a smoothing processing unit that performs a smoothing process by adding a predetermined pixel to the concave portion of the edge portion of the image based on the determination result by the image pattern determination unit. In an image processing apparatus having The image pattern determining unit determines an array of pixels of the input multi-value image data, and the smoothing processing unit is configured to input the input multi-value image data and the pixels determined by the image pattern determining unit. A plurality of levels of smoothing processing performed according to the array and the pixel density of the image, the input multi-value image data, the array of pixels determined by the image pattern determination unit, The intensity of the smoothing process is changed according to the pixel density of the image.
[0013]
Further, the invention described in claim 3 is inputted. Multi-value image data An image pattern determination unit that determines the arrangement of the pixels, and a smoothing processing unit that performs a smoothing process by adding a predetermined pixel to the concave portion of the edge portion of the image based on the determination result by the image pattern determination unit. In an image processing apparatus having The image pattern determining unit determines an array of pixels of the input multi-value image data, and the smoothing processing unit is configured to input the input multi-value image data and the pixels determined by the image pattern determining unit. A plurality of levels of smoothing processing applied according to the array and the character size and pixel density of the image, the input multivalued image data, the array of pixels determined by the image pattern determination unit, and Image text size as well as The intensity of the smoothing process is changed according to the pixel density.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below based on the illustrated embodiments.
[0015]
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.
[0016]
FIG. 1 shows an example of an oblique line image 1 with 45 degrees rising to the right. By changing the density level (pixel width) of the pixel 3 added to the step part 2 of the oblique line over a plurality of stages, the strength of the smoothing process ( It is the figure which showed a mode that the degree of smoothness of a slanting part jaggy changes gradually. In FIGS. 1A to 1E, all the added pixels 3 are added close to the stepped portion (rightward) in common. FIG. 1A shows a case where smoothing processing is not performed, and FIGS. 1B to 1E have density levels of 26, 51, 77 and 102 (ranges of pixel density levels are 0 to 255), respectively. The case where a pixel is added is shown. Further, in common with FIGS. 1A to 1E, the hatched portion of the rectangle indicated by the symbol a in the figure indicates the laser drive signal after pulse width modulation, and the vertical ellipse in the rectangle indicated by the symbol b. The part shows the beam spot of the laser beam irradiated to the photosensitive drum of the laser beam printer to which the present invention is applied, and the curved part with the symbol c shows the output image actually recorded on the recording paper, respectively. It is a representation. As is clear from FIGS. 1A to 1E, the intensity of the smoothing process gradually changes by changing the density level (pixel width) of the pixel added to the stepped portion 2 of the image 1 to a plurality of levels. I understand that. Further, in the case of the image 1 with 45 degrees diagonally rising to the right 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. Note that if the density level (pixel width) of the pixel to be added is further increased than in FIG. 1 (e), the stepped portion 2 becomes thicker and the strength of the smoothing process is weakened.
[0017]
As the pixel 3 added to the image 1 in order to perform the smoothing process, for example, in the case of the image 1 having a diagonal line of 45 degrees rising to the right, the pixel 3 having the density level (pixel width) “102” is used. In the case of another image 1, a pixel 3 having a density level appropriately determined according to the image 1 is added to the step portion 2 or the like.
[0018]
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.
[0019]
In FIG. 2, reference numeral 21 denotes a photosensitive drum as an image carrier. The photosensitive drum 21 is driven to rotate at a predetermined rotational speed in the direction of the arrow by a driving means (not shown). Yes. 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 developers of yellow, magenta, cyan, and black are accommodated. Four color developing devices 24a, 24b, 24c, 24d, a transfer charger 25, and an intermediate transfer belt for transferring and holding toner images of respective colors sequentially formed on the photosensitive drum 21 in a state of being superimposed on each other. 26 are sequentially arranged along the rotation direction of the photosensitive drum 21. Further, around the intermediate transfer belt 26, toner images of a predetermined number of colors superimposed on the intermediate transfer belt 26 are conveyed to positions corresponding to the intermediate transfer belt 26 at a predetermined timing. A transfer roll 27 for transferring images onto the recording paper 20 to be transferred at once, and a conveying belt for conveying the recording paper 20 as a recording medium to which the toner image of the predetermined number of colors is transferred to a fixing device 29 described below. 28 and a fixing device 29 for fixing the toner image on the recording paper 20 conveyed by the conveying belt 28 are disposed.
[0020]
The scorotron charger 22 that uniformly charges the surface of the photosensitive drum 21 is a scorotron that uses two or more discharge wires so that stable and uniform charging is possible even during image formation for the second and subsequent colors. It is desirable to use a charger.
[0021]
As the color developing devices 24a, 24b, 24c, and 24d, for example, a two-component developing device having a known configuration can be used. In order not to come into contact with the surface of the photosensitive drum 21 and the toner image formed on the photosensitive drum 21 for the second and subsequent colors, the spikes of the two-component developer carried on the developing roll pass through the gap. Those arranged so as to face the surface of the drum 21 are used. Further, the developing bias applied to each of the color developing devices 24a, 24b, 24c, and 24d is AC so that the toner image formed on the photosensitive drum 21 is not disturbed and a desired high image quality is obtained. It is desirable to set so as to apply a direct current voltage (DC + AC voltage) on which the voltage is superimposed.
[0022]
FIG. 3 is a schematic configuration diagram showing a laser optical system used in the laser beam printer of FIG.
[0023]
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 driving 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 irradiated onto the surface of the polygon mirror 33 through the collimator lens 32, reflected and deflected by the surface of the polygon mirror 33 rotating at high speed, and then through the fθ lens 34. Scanning exposure is performed on the photosensitive drum 21 along the main scanning direction (the axial direction of the photosensitive drum 21).
[0024]
In the laser beam printer configured as described above, after the surface of the photosensitive drum 21 is uniformly charged to a predetermined potential by the scorotron charger 22, as shown in FIG. The laser optical system 23 scans and exposes an image corresponding to the first color image information to form an electrostatic latent image. The first color electrostatic latent image formed on the photosensitive drum 21 is developed into a toner image by a first color developer, for example, a yellow color developer 24a. The yellow toner image of the first color is electrostatically transferred onto the intermediate transfer body belt 26 by charging of the transfer charger 25 at the transfer position. Thereafter, the photosensitive drum 21 on which the toner image of the first color is transferred onto the intermediate transfer belt 26 is cleaned by a cleaning unit (not shown), and the charging, exposing, and developing steps are performed again with a predetermined number of colors in the same manner as described above. The toner images of four colors of yellow, magenta, cyan, and black, which are sequentially formed on the photosensitive drum 21, are sequentially transferred onto the intermediate transfer belt 26 while being superimposed on each other. The four-color toner images transferred onto the intermediate transfer belt 26 are collectively collected on the recording paper 20 by a transfer roll 27 that contacts the intermediate transfer belt 26 via the recording paper 20 at a predetermined timing. After the transfer, the recording paper 20 is transported to the fixing device 29 by the transport belt 28. 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 to complete the color image forming process.
[0025]
Further, the surface of the photosensitive drum 21 after the transfer process of the toner images of the respective colors is erased from the residual toner charge by a neutralizer (not shown) and the residual toner is removed by a cleaning device having a blade. The residual charge is further erased by the charge eliminating lamp, and it is prepared for the next color image forming step.
[0026]
In this embodiment, an apparatus for forming a full-color image using the intermediate transfer belt 26 as a laser beam printer has been described. However, the present invention is not limited to this and is formed on a photosensitive drum. A toner image of each color is sequentially transferred onto a recording paper or an intermediate transfer medium held on an intermediate transfer drum to form a full-color image or a plurality of photosensitive drums, and each photosensitive drum is formed. It may be a so-called tandem color image forming apparatus or the like that forms a full-color image by sequentially transferring the plurality of toner images thus formed onto a recording sheet that is sequentially conveyed to the transfer position of each photosensitive drum. Of course. Of course, the laser beam printer may be a black and white laser beam printer as described above.
[0027]
FIG. 4 is a block diagram showing an image processing apparatus according to an embodiment of the invention applied to the laser beam printer.
[0028]
As the image data recorded by this laser beam printer, for example, there are used 256 gradations of 8 bits from 0 to 255 and quantized so that the density increases as the value increases. That is, in the case of monochrome image data, “0” represents “white” and “255” represents “black”. In the case of color image data, for example, “red (R), red (R), green (green)”, “magenta (M), cyan (C), yellow (Y)”, “lightness (L ^* ), Hue (H ^* ), Saturation (C ^* ) "Or" L ^* a ^* b ^* In general, one image data is represented by a plurality of components. In this case, for example, an embodiment shown below for each component represented by 256 gradations from 0 to 255 of 8 bits. May be applied in the same manner.
[0029]
In FIG. 4, the input multi-value image data is input to the edge detection unit 40 and the binarization unit 41, and after the multi-value data is binarized by the binarization unit 41, the pattern matching unit 42 Entered. The edge detection unit 40 detects the presence / absence and direction of the edge of the input multi-value image data, adds an edge direction flag to the image data, and outputs the image data. Further, the pattern matching unit 42 performs “binary → multilevel conversion” to reduce jaggy of the binarized data, and further generates a flag indicating the edge direction. The combining unit 43 combines the outputs of the edge detection 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.
[0030]
FIG. 5 shows the internal configuration of the edge detection unit. Each of the 1-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 performs filtering processing on the blocked image data, detects the edge direction of the image data, and outputs 2 bits of the edge direction flag. The delay unit 48 is for synchronizing the input image data with the edge direction flag output from the 3 × 3 filter unit 47. The edge signal adding unit 49 synthesizes the 8-bit image signal output from the delay unit 48 and the 2-bit edge output from the 3 × 3 filter unit 47 and outputs the resultant signal as a 10-bit signal. As shown in FIG. 6, the output signal of the edge signal adding unit 49 is a flag in which the upper 2 bits of 10 bits indicate the edge direction, and the lower 8 bits are an image signal.
[0031]
Next, the 3 × 3 filter unit 47 will be described in more detail with reference to FIG. The input image data is blocked into 3 × 3 9 pixels centering on the pixel of interest. The block image 50 is subjected to a convolution operation using four types of coefficients 51, 52, 53, and 54, and the respective calculation results are four types of edge signals EG-1, EG-2, EG-3, EG. -4. The maximum edge detection unit 55 obtains absolute values of the four types of edge signals EG-1, EG-2, EG-3, and EG-4, and determines the largest of the four absolute values as the edge cancellation unit 56. The edge signal number (any one of 1, 2, 3, 4) indicating the largest absolute value is output to the edge direction flag generation unit 57. The edge direction flag generator 57 receives the maximum edge number output from the maximum edge detector 55 and the four types of edge signals EG-1, EG-2, EG-3, and EG-4. Depending on the maximum edge number, one of the four types of edge signals EG-1, EG-2, EG-3, EG-4 is selected, and the direction of the edge 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, the case where the density decreases from the top to the bottom as shown in FIG. 8A is “upper edge”, and the case where the density decreases from the left to the right as shown in FIG. 8B. Let's say "left edge". In the 2-bit edge direction flag, as shown in FIG. 9, “00” means no edge, “01” means an upper or lower edge, “10” means a right edge, and “11” means a left edge.
[0032]
As described above, the edge direction flag generation unit 57 generates any one of the edge direction flags “01”, “10”, and “11” for all the pixels. In the edge cancellation unit 56, the edge direction flag is reset to “00” when the maximum edge absolute value output from the maximum edge detection unit 55 is equal to or less than a predetermined value.
[0033]
FIG. 10 is a diagram illustrating 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”. The 1-bit signal generated by the binarization unit 41 is blocked using 1-line memories 60 and 61 and input to the 3 × 3 pattern matching unit 62.
[0034]
FIG. 12 is a diagram for explaining the 3 × 3 pattern matching unit 62 in more detail. The data of each of nine pixels that are divided into 3 × 3 blocks around the target pixel using the one-line memories 60 and 61 are looked at. It is connected to the address of the uptable ROM 63. In the look-up table, in the case other than the patterns shown in FIGS. 13 and 14, when the value of the target pixel “e” is “0”, the image data “0” edge direction flag “00” is set to the target pixel. When the value of “e” is “1”, the image data “255” edge direction flag “00” is set to be output. In the case of the patterns shown in FIG. 13 and FIG. The image data and edge direction flag shown in the middle are output and output as 10-bit data in the format shown in FIG.
[0035]
The pattern matching unit 62 has an effect of reducing jaggy in the case where pixels of “255” density are continuous in an oblique direction from the continuity of density values of “255” in the multi-value image data.
[0036]
FIG. 15 illustrates an internal configuration of the synthesis unit 43. The synthesizing unit 43 is a part for synthesizing the outputs of the edge detection unit 40 and the pattern matching unit 42. The synthesis logic focuses on the image data of the pattern matching unit 42 and is input from the pattern matching unit 42 to the synthesizing unit 43. When the image data to be received is “0” or “255”, the image data input from the edge detection unit 40 and the edge direction flag are output from the synthesis unit. If the image data input from the pattern matching unit 42 to the combining unit 43 is not “0” and other than “255”, the image data input from the pattern matching unit 42 and the edge direction flag are combined. The output of the unit 43 is used. As described above, in the synthesizing unit 43, when data other than “0” or “255” is output from the pattern matching unit 42, that is, pixels of “255” density in the multi-value image data are continuously displayed in the oblique direction. In the case where there is, the pixel value generated to reduce the jaggy in the oblique direction is output with priority.
[0037]
In the waveform control screen unit 44, as shown in FIG. 16, 8-bit multi-value image data input from the synthesis unit 43 is converted into an analog value via the D / A converter 71, and selected by the selector 72 by the edge direction flag. The triangular wave is compared with the comparator 73 to generate a laser control signal.
[0038]
Here, as shown in FIG. 17, the waveform of the triangular wave selected by the selector 72 has a period twice that of the pixel clock, and has the same period as that of the triangular wave A and the triangular wave B and the pixel clock that are 180 degrees out of phase. A triangular wave C. FIG. 18 shows the relationship between the edge direction flag and the selected triangular wave.
[0039]
Here, an example will be described. When image data and an edge direction flag as shown in FIG. 19 are input to the waveform control screen, 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 place where a laser beam is irradiated onto a photosensitive drum and is output as a black image on a sheet. Here, FIG. 21 shows a case where a laser control signal is generated using a triangular wave C having the same period as the pixel clock without controlling the waveform of the image data shown in FIG. Comparing FIG. 21 and FIG. 20, in FIG. 18 where the waveform is born, the laser control signal is concentrated in the central portion, whereas in FIG. 20, the laser on signal is divided into three. In FIG. 20, a clear electronic latent image can be generated on the photosensitive member. Also, 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, and there is no normal edge state. That is, when the edge direction flag is “00”, the triangular wave A having a cycle twice the cycle of the pixel clock is selected. This means that, for example, in a printer capable of printing with a pixel density of 400 dpi (dots / inch), an output image is generated using a universal screen of 200 lpi (lines / inch). The reason for this is that when outputting a highlight portion having a low density, as shown in FIGS. 22A and 22B, a laser control signal is generated using a triangular wave having the same cycle as the pixel clock ( Compared with FIG. 22A), the laser-on time is very short, and when the laser irradiation time is very short as described above, a latent image can be stably formed electronically on the photosensitive member. This is because it is difficult to output the gradation of the image data accurately as a result.
[0040]
As described above, the jaggy reduction method in the case where the pixels indicating the density value of “255” in the multi-level document are continuously arranged in the oblique direction has been described. When text data is inserted into normal multi-value image data (for example, a photograph), most of the text data is described at the maximum density. Therefore, the method disclosed this time is used for character / line drawing in multi-value image data. This is a very effective means for improving the image quality.
[0041]
By the way, the image processing apparatus according to this embodiment is configured to change the intensity of the smoothing process according to the character size.
[0042]
That is, as shown in FIG. 10, a character size signal synchronized with the multi-value input image data is input to the pattern matching unit 42 in addition to the multi-value input image data. As the character size signal, a signal indicating the size of the character normally included in the font data representing the character is used. Here, as shown in FIG. A signal represented by 2 bits is used. A signal indicating the size of the character is input to the multiplication coefficient generation unit 81 via the one-line memory 80, and an output signal of the multiplication coefficient generation unit 81 is input to the multiplier 82. In this multiplier, the 8-bit image data output from the 3 × 3 pattern matching unit 62 is multiplied by the multiplication coefficient a output from the multiplication coefficient generation unit 81.
[0043]
FIG. 13 is a diagram showing the inside of the LUT of the 3 × 3 pattern matching unit 62 in FIG. The pixel of interest is a 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.
[0044]
With this configuration, the image data that is the output of the 3 × 3 pattern matching unit 62 in FIG. 10 is multiplied by the coefficient a determined by the character size signal by the multiplier 81, so that the final multivalue is obtained. The value of the output image data can be determined.
[0045]
In the above configuration, in the image processing apparatus according to this embodiment, even when smoothing processing is performed on image data including characters as described below, character collapse may occur depending on the size of the characters. In addition, it is possible to prevent a sense of incongruity at the change point as in the case where the presence or absence of the font data or the smoothing process is switched according to a predetermined character size or the like.
[0046]
That is, in the image processing apparatus, when the 3 × 3 pattern matching unit 62 performs the smoothing process on the multivalued image data, the image data that is the output of the 3 × 3 pattern matching unit 62 is applied to the image data as shown in FIG. By multiplying the 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.
[0047]
Therefore, for example, when the character “line” as shown in FIG. 25 is recorded: 彳, as shown in FIG. Accordingly, as shown in FIG. 24, the multiplier 82 can multiply the output of the 3 × 3 pattern matching unit 62 by a predetermined multiplication coefficient a to change the intensity of the smoothing process in a plurality of stages. The multiplication factor a becomes smaller as the character becomes smaller, and the strength of the smoothing process becomes weaker. Therefore, even if the character becomes smaller, as shown in FIG. 26 (b), the intensity of the smoothing process becomes weaker, for example, the density level of the pixel added to the 45 ° hatched recess is reduced to 51. It can be seen that the value of the shortest distance L2 between the output images is larger than the value of L1, so that the characters are not easily crushed.
[0048]
As described above, in the above-described embodiment, by changing the strength of the smoothing process to a plurality of stages according to the character size, even when the smoothing process is performed on the image data including the character, the character size is changed depending on the character size. It is possible to prevent the occurrence of crushing, and it is also possible to prevent a sense of incongruity at the changing point, such as when the font data or smoothing processing is switched at a predetermined character size or the like. ing.
[0049]
Embodiment 2
FIG. 27 shows the second embodiment of the present invention. The same reference numerals are given to the same portions as those of the first embodiment, and in this second embodiment, not the character size. The intensity of the smoothing process is changed according to the pixel density.
[0050]
That is, in the image processing apparatus according to the second embodiment, as shown in FIG. 27, the pattern matching unit 42 receives a signal indicating the pixel density synchronized with the multi-value input image data, in addition to the multi-value input image data. Have been entered. As this 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 the character size, font, etc. As shown in FIG. 28, a signal displayed in 2 bits according to the pixel density is used. The signal indicating the pixel density 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, the 8-bit image data output from the 3 × 3 pattern matching unit 62 is multiplied by the multiplication coefficient b output from the multiplication coefficient generation unit 81. FIG. 29 is a diagram showing the inside of the multiplication coefficient generator of FIG.
[0051]
By adopting such a configuration, the final multi-value output image is obtained by multiplying the image data that is the output of the 3 × 3 pattern matching unit 62 in FIG. 27 by the coefficient b determined by the pixel density signal by the multiplier 81. The value of the data can be determined.
[0052]
As described above, in the above-described embodiment, by changing the strength of the smoothing process to a plurality of levels according to the pixel density, even when the smoothing process is performed on the image data including characters, the characters are crushed depending on the pixel density. In addition, it is possible to prevent the occurrence of a sense of incongruity at the change point, such as when the font data or smoothing process is switched with a predetermined character size or the like. .
[0053]
Furthermore, in this embodiment, since the strength of the smoothing process is changed to a plurality of levels according to the pixel density, even a large character can be compared with the case where the strength of the smoothing process is changed to a plurality of levels according to the character size. Even when the pixel density is high, that is, when a character having a large number of strokes is recorded, the strength of the smoothing process can be changed in a plurality of stages, which is more effective in preventing the character from being crushed.
[0054]
Other configurations and operations are the same as those of the above-described embodiment, and thus description thereof is omitted.
[0055]
Embodiment 3
FIG. 30 shows a third embodiment of the present invention. The same reference numerals are given to the same parts as those in the first embodiment. In the third embodiment, the character size and the pixel density are shown in FIG. The intensity of the smoothing process is changed according to both of the above.
[0056]
That is, in the image processing apparatus according to the third embodiment, as shown in FIG. 30, the pattern matching unit 42 causes the character size and pixel density synchronized with the multi-value input image data to be separated from the multi-value input image data. Is input. The signal indicating the character size and the pixel density is a table (not shown) based on the signal indicating the character size normally included in the font data indicating the character and the data indicating the character size and the font. Etc., a signal indicating a value corresponding to the pixel density is used for each character. Here, as shown in FIG. 31, each of the characters is displayed with 2 bits according to the character size and the pixel density. A signal is used. The signal indicating the character size and the signal indicating the pixel density are input to the multiplication coefficient generators 92 and 93 via the one-line memories 90 and 91 and output signals of the multiplication coefficient generators 92 and 93. Is input to the multiplier 94. In the multiplier 94, the 8-bit image data output from the 3 × 3 pattern matching unit 62 is multiplied by the multiplication coefficients a and b output from the multiplication coefficient generation units 92 and 93. FIG. 32 is a diagram showing the inside of the multiplication coefficient generators 92 and 93 of FIG.
[0057]
With this configuration, the image data that is the output of the 3 × 3 pattern matching unit 62 in FIG. 30 is multiplied by the multiplier 94 by the signal indicating the character size and the coefficients a and b determined by the pixel density signal. As a result, the final multi-value output image data value can be determined.
[0058]
As described above, in the above embodiment, by changing the strength of the smoothing process to a plurality of levels according to the character size and the pixel density, even when the smoothing process is performed on the image data including the character, Depending on the pixel density, it is possible to prevent characters from being crushed and to give a sense of incongruity at the change point, such as when switching font data or smoothing processing with a predetermined character size. Can be prevented.
[0059]
Further, in this embodiment, since the strength of the smoothing process is changed according to both the character size and the pixel density, it is possible to perform the smoothing process considering both the character size and the pixel density. Therefore, it is possible to further prevent the characters from being crushed and to record an image with high resolution and smoothing processing.
[0060]
Other configurations and operations are the same as those of the above-described embodiment, and thus description thereof is omitted.
[0061]
In the configuration of FIG. 30 described in the above embodiment, a multiplication coefficient generator A and a multiplication coefficient generator B are provided separately from the LUT of the 3 × 3 pattern matching unit, and the LUT output of the 3 × 3 pattern matching unit is provided. The final multi-value output image data value is determined by multiplying the pixel data that is a factor a determined by a character size signal and a coefficient b determined by a pixel density signal by a multiplier. 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 combined into one LUT. In this case, however, the final multi-value output image data value after the multiplication result needs to be set in advance for the image data to be output from the LUT. Moreover, although LUT is described as ROM, it is also possible to adopt a RAM configuration.
[0062]
【The invention's effect】
The present invention has the above-described configuration and operation, and even when image data including characters is subjected to smoothing processing, it is possible to prevent the characters from being crushed depending on the size of the characters or the pixel density. In addition, it is possible to provide an image processing apparatus that does not give a sense of incongruity at the change point, as in the case where the presence or absence of smoothing processing is switched between font data and a predetermined character size.
[Brief description of the drawings]
FIG. 1A to FIG. 1E are schematic views respectively showing an embodiment of an image processing apparatus according to the present invention.
FIG. 2 is a block 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 showing a ROS of the same color image forming apparatus.
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 edge detection methods, 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 binarization unit.
FIG. 12 is an explanatory diagram showing a pattern matching unit.
FIG. 13 is an explanatory diagram showing a detection state of a pattern matching unit.
FIG. 14 is an explanatory diagram showing 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 chart showing types of triangular waves.
FIG. 19 is a chart showing the types of triangular waves to be selected.
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 a character size signal.
FIG. 24 is a chart showing multiplication coefficients.
FIGS. 25A and 25B are schematic diagrams respectively showing examples of characters.
FIGS. 26A and 26B are schematic views showing examples of characters, respectively.
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 character size signals and image density signals, respectively.
32 (a) and 32 (b) 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 showing the operation of the image processing apparatus, respectively.
FIGS. 35A and 35B are schematic diagrams showing examples of characters, respectively.
[Explanation of symbols]
40 edge detection unit, 41 binarization unit, 42 pattern matching unit, 43 synthesis unit, 44 waveform control screen unit.

Claims (3)

An image pattern determination unit that determines the arrangement of pixels of the input multivalued image data , and a smoothing process by adding predetermined pixels to the concave portion of the edge portion of the image based on the determination result by the image pattern determination unit In the image processing apparatus including the smoothing processing unit, the image pattern determination unit determines an array of pixels of the input multi-valued image data, and the smoothing processing unit includes the input multi-valued image data. A plurality of levels of smoothing processing to be performed according to the pixel arrangement determined by the image pattern determination unit and the character size of the image, the input multi-value image data, and the image pattern determination unit wherein an array of pixels which are determined, varying the intensity of the smoothing processing in accordance with the character size of the image by The image processing apparatus. An image pattern determination unit that determines the arrangement of pixels of the input multivalued image data , and a smoothing process by adding predetermined pixels to the concave portion of the edge portion of the image based on the determination result by the image pattern determination unit In the image processing apparatus including the smoothing processing unit, the image pattern determination unit determines an array of pixels of the input multi-valued image data, and the smoothing processing unit includes the input multi-valued image data. A plurality of levels of smoothing processing to be performed according to the pixel arrangement determined by the image pattern determination unit and the pixel density of the image, and the input multi-valued image data and the image pattern determination unit It is characterized and sequences of pixels determined, varying the intensity of the smoothing processing in accordance with the pixel density of the image by Image processing apparatus. An image pattern determination unit that determines the arrangement of pixels of the input multivalued image data , and a smoothing process by adding predetermined pixels to the concave portion of the edge portion of the image based on the determination result by the image pattern determination unit In the image processing apparatus including the smoothing processing unit, the image pattern determination unit determines an array of pixels of the input multi-valued image data, and the smoothing processing unit includes the input multi-valued image data. A plurality of levels of smoothing processing to be performed according to the pixel arrangement determined by the image pattern determination unit and the character size and pixel density of the image, and the input multi-value image data and the image an array of pixels which are determined by the pattern determining section, the strength of the smoothing processing in accordance with the character size and pixel density of the image The image processing apparatus characterized by changing the.

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