JP3054315B2 - Image processing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and apparatus, and more particularly to an image processing method and apparatus for performing a scaling process on a digital binary image.

[0002]

2. Description of the Related Art When scaling a binary image, instead of scaling the binary image itself, first, contour information of a character / line drawing area of the binary image is extracted, and based on the extracted contour information. It has been proposed to generate a scaled image. Specifically, an outline vector is extracted from the binary image, an outline vector that is smoothly scaled at a desired magnification (arbitrary) is created in the extracted outline vector format, and 2 is generated from the smoothly scaled outline vector.
This is to regenerate the value image. However, this scaling method focuses on a black pixel area in a white background (base) in a binary image, extracts a contour vector at a boundary between the white pixel area and the black pixel area, and processes the contour vector loop unit. Noise removal and smoothing are also applied to isolated points peculiar to the pseudo-halftone image, black pixel connected components of several pixels connected in a scale shape, and dither patterns. In some cases, the apparent density obtained by the area gradation expression of the image changes, or the specific texture is further emphasized, resulting in lower image quality.

[0003]

Accordingly, when an image is scaled, a method of dividing the image into an image having only a character / line drawing component and an image having only a pseudo halftone component, and performing a scaling process on each of them. Has also been proposed. However, in the above conventional example,
Image quality degradation may occur due to an erroneous determination of an image area, which is likely to occur when an image has characters in the pseudo halftone area or when noise is included in the characters.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and provides an image processing method capable of obtaining a scaled image of good image quality even when an erroneous determination occurs between a character / line drawing component and a pseudo halftone component. It is intended to provide the device.

[0005] Another object of the present invention is to perform two types of image processing by applying an appropriate scaling process to a character / line image component and an appropriate scaling process to a pseudo halftone component on an input image. It is an object of the present invention to provide an image processing method and apparatus for selecting and combining two images by image area determination.

Another object of the present invention is to limit the black pixels in the input to the scaling process suitable for character / line drawing components to black pixels determined to be character / line drawing components and black pixels in the vicinity thereof. It is another object of the present invention to provide an image processing method and an image processing method in which the required memory capacity and processing time are not increased while performing such processing.

[0007]

In order to achieve the above object, an image processing method according to the present invention has the following arrangement.
That is, an image area determining step of determining whether each pixel in the binary image belongs to a character / line drawing area or a pseudo halftone area, and a first step of scaling the area determined to be a character / line drawing area
, A second scaling step for scaling an area determined as a pseudo halftone area, and a scaling step for each of the first and second scaling steps using the result of the image area determination step. Selecting and combining the multiplied image for each pixel.

In order to achieve the above object, an image processing apparatus according to the present invention has the following arrangement. That is, an image area determining unit that determines whether each pixel in the binary image belongs to a character / line drawing area or a pseudo halftone area, and a first scaling unit that scales the area determined to be a character / line drawing area. Multiplying means, second scaling means for scaling an area determined as a pseudo halftone area, and the first scaling means according to the determination result of the image area determining means.
And a selecting / combining unit for selecting and combining the images scaled by the respective second scaling units.

[0009]

In the above arrangement, it is determined whether each pixel in the binary image belongs to the character / line drawing area or the pseudo halftone area, and the image determined as the character / line drawing area is scaled up and down. The area determined as the halftone area is scaled. Then, in accordance with the determination result of the image area determining means, the operation is performed such that the images scaled by the first and second scaling means are selected and combined.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

[First Embodiment] FIG. 1 is a block diagram showing the configuration of an image processing apparatus according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a binary image acquisition unit which acquires (inputs) a digital binary image to be subjected to a scaling process and outputs a binary image in a raster scanning format. Reference numeral 2 denotes an image area determination unit.
For each pixel of the binary image data (signal) in the raster scanning format output from the binary image acquisition unit 1, an image area containing a pseudo halftone component or another component (hereinafter referred to as a character / line drawing component) ) Is determined. Reference numeral 3 denotes an image area determination result scaling section that scales the area information output from the image area determination section 2. Reference numeral 4 denotes an outline extracting image creating unit which, in accordance with the image area determined by the image area determining unit 2, outputs the character / line image components of the raster image binary image data output from the binary image acquiring unit 1 and its components. Binary image information composed of surrounding black pixels is created. Reference numeral 5 denotes an outline resizing unit which inputs raster scanning binary image data output from the outline extraction image generation unit 4 and extracts outline vectors from the input image information. Further, the image is smoothed and scaled in the form of the extracted outline vector data, and from the obtained smoothed and scaled outline data, a binary image represented by the data is converted into a raster image binary image. It is reproduced as data to obtain a scaled image.

Reference numeral 6 denotes a pseudo-halftone scaling unit which receives raster scanning binary image data from the binary image acquisition unit 1 and scales the data in a manner different from that of the outline scaling unit 5. 7
Is a selection / synthesis unit, which outputs the output 16 of the outline scaling unit 5;
The output 17 of the pseudo halftone scaling unit 6 is input, and the output 16 is determined according to the image area determination result 14 from the image area determination result scaling unit 3.
And 17 are selected to obtain a combined scaled image. Reference numeral 8 denotes a binary image output unit for displaying the scaled image obtained by the selection / synthesis unit 7, taking a hard copy, or outputting the image to a communication path or the like.

Hereinafter, the configuration and operation of each part will be sequentially described.

The binary image acquisition unit 1 is a known raster scanning type binary image output device or the like which reads an image with an image reader, binarizes the image, and outputs it in a raster scanning format.
However, a device that takes in data from a storage medium storing a binary image or a device that converts an image captured by a still camera into a binary image may be used.

Next, FIG. 2 shows an example of the configuration of the image area determination section 2.

In FIG. 2, reference numeral 21 denotes a data holding unit which sequentially updates and holds each pixel value in a small area required for the image area determination processing. For example, as shown in FIG. 3, the data holding unit 21 converts the digital binary image data input in the raster scanning format into a maximum of 8 ×
8, a data group 203 of 64 pixels is held. Then, the position of the target pixel is updated (moves sequentially in a raster scanning format).
At the same time, the content of the held data is updated to the data of the corresponding area.

FIG. 4 is a block diagram showing a configuration example of the data holding unit 21.

Reference numeral 24 denotes a line buffer unit composed of, for example, a FIFO, which holds data corresponding to seven rasters (scanning lines) immediately before the raster being input. Reference numeral 25 denotes a latch group, which holds data for 8 pixels per raster, that is, a total of 64 data.

Referring again to FIG. 2, reference numeral 22 denotes an image area determination condition part, which is in the small area based on pixel group data including the pixel of interest forming the small area output from the data holding part 21. It is determined whether the pixel of interest is a pixel in the pseudo halftone area. The image area determination condition unit 22 includes an isolated pixel determination unit 26, an isolated pixel region determination unit 27, and a periodicity determination unit 2.
8. The high-frequency component determination unit 29 includes four types of determination units that determine whether different conditions are satisfied. Here, if any one of these conditions is satisfied, it is determined that the pixel of interest is a pixel of a pseudo halftone component.

The isolated pixel determination unit 26 determines whether the pixel of interest is an isolated pixel.

As shown in the pixel matrix 204 of FIG. 5, this corresponds to a 3 × 3 area pixel matrix 204 having a width of 3 pixels in the main scanning direction and a width of 3 pixels in the sub-scanning direction centering on the target pixel 201. If the pixel values other than the pixel of interest are all the same value (all white pixels or all black pixels) and the pixel of interest is different from the peripheral pixels, the pixel of interest 201
Is determined to be an isolated pixel.

The determination result R (i, j) of the isolated pixel determination unit 26
Let V (i, j) denote the pixel value at the i-th row and j-th column, and when V (i, j) = 1 means a black pixel and when V (i, j) = 0 means a white pixel, It can be realized by a logic circuit that executes the following logic equation.

R (i, j) = (V (i, j) NOT (V (i-1, j)
-1)) NOT (V (i-1, j)) NOT (V (i-1, j + 1)
) ・ NOT (V (i, j-1)) ・ NOT (V (i, j + 1)) ・
NOT (V (i + 1, j-1)) / NOT (V (i + 1, j)) / NO
T (V (i + 1, j + 1)))) + (NOT (V (i, j)). V (i-1,
j-1) V (i-1, j) V (i-1, j + 1) V (i, j-1) V (i, j
j + 1) V (i + 1, j-1) V (i + 1, j) V (i + 1, j + 1) where "." is the logical product and "+" is the OR, and NO
T (x) means the inversion of the logical value x. However, the priority of the operation is “NOT (x) >> +”.

The isolated pixel area determining section 27 determines whether or not the pixel of interest is in the isolated pixel area. A specific example is shown in FIG. In FIG. 6, the pixel matrix 205 has a width of 4 pixels in the main scanning direction and a width of 4 ×
It consists of 16 pixels in a 4 pixel area.

For each pixel in the pixel matrix 205, as shown in FIG. 7, four pixels ((k,
L-1) above, (k, L + 1) below, (k
(−1, L) is referred to as the left, and (k + 1, L) is referred to as the right.) All pixels having the same value (that is, white pixels or black pixels)
And whether the value is different from that of the pixel at the position (k, L). When each pixel value of the 4 × 4 pixel area is a pixel at the position of (k, L), 16 results are obtained. It is determined that the target pixel 201 of the 4 × 4 pixel area 205 is in the isolated pixel area. That is, the pixel of interest is 201
It is determined whether or not there are two or more isolated pixels (that is, black or white pixels that are not connected to any of the upper, lower, left, and right) in the 16 pixels of the neighboring pixel area 205, For example, when there are two or more pixels, it is determined that the target pixel 201 is in the isolated pixel area.

The periodicity judging section 28 judges whether or not the pixel values are the same in a predetermined pixel cycle.
Specifically, of the 64 pixels in the 8 × 8 pixel area of 8 pixel width in the main scanning direction and 8 scanning widths in the sub-scanning direction shown at 202 in FIG. 3, all 64 pixels are white pixels, Except for the case where all pixels are black pixels, four pixels having a positional relationship of 4 pixels apart from each other in the main scanning direction and / or 4 pixels apart from each other in the sub-scanning direction (for example, A, B, and H hatched in FIG. 3). C,
It is determined whether all the pixel values of the pixels match during D). In an 8 × 8 pixel area as shown in FIG. 3, a set of four pixels having a relative positional relationship such as 16 types of A, B, C, and D can be defined. In each of these 16 cases, it is checked whether or not the pixel values of all four pixels are equal, and if they are equal, for example, it is determined whether or not 14 or more cases. If so, it is determined that the pixel is in a periodic portion (ie, a dither portion), except when all 64 pixels are white pixels or all black pixels.

The high frequency component judging section 29 judges whether or not a density change has occurred between adjacent pixels. Specifically, as shown in FIG.
30 combinations of one pixel adjacent in the horizontal (main scanning) direction among 36 pixels in a 6 × 6 pixel area having a width of 6 pixels in the main scanning direction and a width of 6 scanning lines in the sub-scanning direction (see FIG. (Indicated by a vertical double-headed arrow), it is checked whether there are 28 or more combinations having different pixel values between adjacent two pixels, for example, if there are 28 or more combinations. Is determined to be in the high frequency component region of the image data.

Referring again to FIG. 2, reference numeral 23 denotes a four-input OR circuit which includes an isolated pixel determination unit 26 and an isolated pixel region determination unit 2.
7. The outputs of the periodicity determination unit 28 and the high-frequency component determination unit 29 are input and the logical sum of them is output. This output is used as the output of the image area determination unit 2. That is, OR circuit 2
3 is a pseudo halftone when it is determined that the pixel of interest is an isolated point, or that the pixel of interest is an isolated pixel area, a periodic pixel area, or a high-frequency component area. It outputs a signal indicating that it is an area.

The above is the configuration of the image area separation unit 2 in FIG. 2 and the processing contents thereof. Note that the various thresholds used for the determination in the image area determination unit 2 are not limited to the above values, and are set according to, for example, the resolution of the input image and other states.

Next, the image area determination result scaling section 3 receives the output 13 of the image area determination section 2 (which can be considered as a raster scanning binary image having the determination result as pixel values), and (Magnification equal to the magnification used in the outline scaling unit 5). The image area determination result scaling unit 3 performs a well-known scaling process of repeatedly outputting the same input pixel value if the image is enlarged, and thinning out the pixel if the image is reduced, by the number of times corresponding to the magnification. ing.

The outline extracting image creating section 4 reduces the number of pixels input to the outline scaling section 5 in such a manner as not to affect the scaling result of the outline scaling section 5 as much as possible. 2, the output 12 of the isolated pixel determination unit 26, the output 13 of the image area determination unit 2, the output 10 of the binary image acquisition unit 1, and the input 2 of the outline scaling unit 5.
The value image data 15 is output in a raster scanning format. That is,
In the input image, only the pixel of the character / line drawing component and the surrounding black pixels are output.

FIG. 9 shows an example of the configuration of the outline extracting image creating section 4.

The outline extracting image creating section 4 outputs a signal indicating a black pixel only when the target pixel satisfies the following three conditions. The first condition is that the target pixel is not an isolated point. This can be obtained by inverting the output 12 of the isolated pixel determination unit 26 of the image area determination unit 2. The second condition is as shown at 402 in FIG.
One or more of the 25 pixels in a 5 × 5 area of 5 pixels in the main scanning direction and 5 pixels in the sub-scanning direction with the target pixel 401 as the center are character / line drawing components. This can be constituted by a data holding unit 43 equivalent to that in FIG. 4 and an OR circuit 44 for inputting signals for the above 25 pixels. The data holding unit 43 receives the result obtained by inverting the output of the image area determination unit 2 by the inverter 46, and outputs the output inversion result of the image area determination unit 2 having a total of 25 pixels in the 5 × 5 area. The third condition is that the target pixel of the input image is a black pixel.
This can be obtained by using the output 10 of the binary image acquisition unit 2. Using the FIFO buffers 42 and 47 and the synchronization control circuit 41, the signals indicating the above three conditions are input to the AND circuit 45 while synchronizing with each other, and the output is output to the output 15 of the outline extraction image creating unit 4. And
Here, as the second condition, an example in which a 5 × 5 region centering on the target pixel is referred to has been described, but the size and shape of the region such as a 7 × 7 region may be changed.

Next, the outline scaling unit 5 will be described.

As shown in FIG. 11, the outline scaling unit 5
Includes an outline extraction unit 51, an outline smoothing / magnification unit 52, and a binary image reproduction unit 53. Specifically, the output of the outline extraction image creating unit 4 is input, an outline vector (coarse contour vector) is extracted by the outline extraction unit 51, and the extracted outline is extracted by the outline smoothing / magnification unit 52. An outline vector that is smoothly scaled at a desired magnification (arbitrary) in a vector representation state is created, and a binary image reproducing unit 53 is created.
In step 2, a binary image is reproduced from the smoothly scaled outline vector. As a result, a high-quality image scaled at a desired magnification is generated.

FIG. 12 shows a scanning form of the raster scanning type binary image data outputted from the outline extracting image forming section 4 of the embodiment.
The scanning form of the raster scanning type binary partial image data 1 is also shown as an input. The outline extracting unit 51 receives the raster-scan type binary image data output from the outline extracting image creating unit 4 in such a format.

In FIG. 12, reference numeral 501 denotes a certain pixel of the binary image during raster scanning, and reference numeral 502 denotes a nine-pixel area including eight pixels near this pixel. The outline extraction unit 51 moves the pixel of interest 501 in the raster scanning order, and checks the state of each pixel (white pixel or black pixel) in the 9-pixel area indicated by 502 for each pixel of interest. Then, a contour vector (horizontal vector or vertical vector) existing between the pixel of interest 501 and a pixel adjacent to the pixel of interest 501 is detected, and if an outline vector exists, data of the start point coordinates and direction of the side vector is extracted. Then, a coarse contour vector is extracted while updating the connection relationship between the side vectors.

FIG. 13 shows the target pixel 501 and the target pixel 50.
An example of an extraction state of a contour vector between one neighboring pixel is shown.

In FIG. 13, △ indicates the starting point of the vertical vector (or the ending point of the horizontal vector), and ○ indicates the starting point of the horizontal vector (or the ending point of the vertical vector).

FIG. 14 shows the outline extraction unit 5 described above.
FIG. 6 is a diagram illustrating an example of a coarse contour vector loop extracted by No. 1; Here, each cell separated by a lattice is
The pixel positions of the input image are shown, and blank cells indicate white pixels, and circles filled with dot patterns indicate black pixels.

As in FIG. 13, .DELTA. Represents the starting point of the vertical vector, and .largecircle. Represents the starting point of the horizontal vector.
As can be seen from the example of FIG.
In step 1, a horizontal vector and a vertical vector having a different length are extracted from a region where black pixels are connected as a coarse contour vector loop that is alternately continuous. However, the direction in which the extraction proceeds is such that the black pixel area is on the right side of the direction in which the extraction proceeds. The starting point of each coarse contour vector is extracted as an intermediate position between each pixel of the input image. That is, when the location of each pixel is represented by an integer (x, y), the starting point of the extracted vector is a value obtained by adding 0.5 to each coordinate value or subtracting 0.5. More specifically, a line portion having a width of one pixel in the original image is also extracted as a coarse contour loop having a significant width.

The group of coarse contour vector loops thus extracted is output from the outline extraction unit 51 in FIG. 11 in a data format as shown in FIG. That is, it is composed of the total number of coarse contour loops “a” extracted from the image and each coarse contour loop data group from the first contour loop to the a-th contour loop. Each coarse contour loop data includes the total number of start points of the contour vectors existing in the coarse contour loop (which can also be considered as the total number of contour side vectors), and the starting point coordinates of each contour side vector (in the order in which the loop is formed). It is composed of a column of values (x-coordinate value, y-coordinate value) (starting points of horizontal vectors and starting points of vertical vectors are alternately arranged).

Next, the outline smoothing / magnifying unit 52 shown in FIG. 11 receives the coarse contour vector data (see FIG. 15) output from the outline extracting unit 51, smoothes the data, and scales it to a desired magnification. The processing is performed on the form of outline vector data (coordinate values).

FIG. 16 shows a more detailed configuration of the outline smoothing / magnifying unit 52.

In FIG. 16, reference numeral 54 denotes a magnification setting unit, and 55 denotes a first smoothing / magnification unit. The first smoothing / magnifying unit 55 performs smoothing / magnifying processing on the input rough contour data at the magnification set by the magnification setting unit 54. This processing result is further smoothed in the second smoothing unit 56,
Get the final output.

The scaling setting section 54 may pass a value set in advance by a dip switch, a dial switch, or the like to the first smoothing / magnifying section 55 or an external I / F (interface). ) May be provided, for example, in a portion that gives information on how many times the image size given as input is independently set in the main scanning (horizontal) direction and the sub-scanning (vertical) direction. is there.

The first smoothing / magnifying unit 55 includes a magnification setting unit 5
Then, smoothing / magnification processing is performed by obtaining the magnification information from step 4.

FIG. 17 shows an example of a hardware configuration for realizing the outline smoothing / magnification processing. In FIG.
0 is an outline extraction circuit, 511 is a CPU, 512 is a disk device, 513 is a disk I / O, and 514 is a CP.
A ROM that stores the operation processing procedure (programs and various data) of U511. 515 is an I / O port, 5
16 is a RAM (random access memory) and 517 is a bus connecting the above blocks.

The outline extraction unit 51 in FIG. 11 stores a file (coarse contour vector data) in the disk device 512 in the data format shown in FIG. CPU 511
Operates according to the procedure given in FIG. 18 and executes outline smoothing / magnification processing.

First, in step S1, the disk I / O 51
Then, the elementary contour data stored in the disk device 512 is read out via the storage device 3 and read into the working memory area (not shown) of the RAM 516. Next, first smoothing and scaling are performed in step S2.

The first smoothing process is performed for each closed loop of the elementary contour data. Each contour side (horizontal vector or vertical vector) vector of each elementary contour data is sequentially focused on, and the vector of each contour of interest is up to three vectors before and after each of them (that is, before the side of interest, 3
The book, the side of interest, and a total of up to seven side vectors after the side of interest, up to seven). The contour points after the first smoothing as the first smoothing result for the side are defined. And
Coordinate values of contour points after the first smoothing and additional information indicating whether or not the contour points are corner points (hereinafter referred to as corner point information)
Is output. Here, the corner point means a point located at a meaningful corner, and excludes a corner point due to a notched portion or a notch due to noise or other factors. By the way, a contour point after the first smoothing determined as a corner point (hereinafter, referred to as a corner point) is not smoothed by the subsequent second smoothing, that is, its position is treated as a fixed point. In other words, the contour points after the first smoothing that are not determined to be corner points (hereinafter, referred to as corner points)
(Referred to as a corner point) will be further smoothed by the second smoothing process in the subsequent stage.

FIG. 19 shows this state, that is, the noticed rough contour side vector Di, three side vectors before the noticed rough contour side vector, Di-1, Di-2, Di-3, and the noticed rough contour side vector. , Three side vectors Di + 1, Di +
2, Di + 3, and the contour points after the first smoothing defined for the side Di of interest. That is, a vector (a vector in an oblique direction is allowed) connecting the contour points thus redefined is constructed.

The first smoothing process has been described above.
The data after the first smoothing is sequentially constructed in a predetermined area of the RAM 516. Thus, after finishing the process of step S2 in FIG. 18, the CPU 511 performs the second smoothing process of step S3.

In the second smoothing process, data after the first smoothing is input. That is, the number of closed loops, the number of contour points for each closed loop, the coordinate value data sequence of the first smoothed contour point for each closed loop, and the additional information data sequence for the first smoothed contour point for each closed loop And outputs contour point data after the second smoothing. The contour data after the second smoothing is
For example, as shown in FIG. 20, it is composed of a closed loop number (N), a contour point number (Li) table for each closed loop, and a coordinate data string of second smoothed contour points for each closed loop.

The outline of the second smoothing process will be described below with reference to FIG. Similar to the first smoothing, the second smoothing is performed for each contour loop, and the processing is performed for each contour point in each contour loop.

If the contour point of interest is a corner point for each contour point, the input contour point coordinate value itself is used as the second smoothed contour point coordinate data for the contour point of interest. That is, nothing is changed.

When the contour point of interest is a non-square point, a value obtained by a weighted average of the coordinate values of the front and rear contour points and the coordinate values of the contour point of interest is used as the value of the contour point of interest. Is the second smoothed contour point coordinate value. That is,
Let the noted input contour point, which is a non-corner point, be Pi (xi, yi),
The immediately preceding contour point in the input contour loop of Pi is Pi-1 (x
i-1, yi-1), and the contour point immediately after is Pi + 1 (xi + 1, yi + 1)
Further, assuming that the second smoothed contour point with respect to the target input contour point Pi is Qi (x'i, y'i), x'i = ki-1.xi-1 + ki.xi + ki + 1.xi + 1 y′i = ki−1 · yi−1 + ki · yi + ki + 1 · yi + 1 (1) Here, ki-1 = ki + 1 = 1/4, ki
= １ ／.

In FIG. 21, points P0, P1, P2, P3,
P4 is a part of the input sequence of the first smoothed continuous contour points, and P0 and P4 are corner points, P1, P2 and P3.
Indicates a non-corner point. The processing results at this time are indicated by points Q0, Q1, Q2, Q3, and Q4, respectively. Since P0 and P4 are corner points, their coordinate values become the coordinate values of Q0 and Q4, respectively. The point Q1 is
A value calculated from P0, P1, and P2 in accordance with the above-described equation has a coordinate value. Similarly, Q2 is derived from P1, P2, P3
Numeral 3 has, as coordinate values, values calculated from P2, P3, and P4 according to the above equation.

The CPU 511 thus operates the RAM 5
The second smoothing process is performed on the first smoothed contour data in a predetermined area on the second image 16. In this processing, the processing proceeds in order from the first loop to the second loop, the third loop, and the like, and the processing for all the loops ends, and the second smoothing processing ends. In the processing of each loop, the processing proceeds to the second point and the third point in order from the first point, and when the processing shown in Expression (1) is completed for all the contour points in the corresponding loop, After the processing, the processing proceeds to the next loop.

When there are L contour points in the loop, the point before the first point is the L-th point.
The point after the point is the first point. As described above, in the second smoothing processing, the same total number of loop points as the first smoothed contour data to be input, and the number of contour points on each loop remain unchanged, and the same number of contour point data is generated. CPU 511
Outputs the above result to another area of the RAM 516 or the disk device 512 in the form shown in FIG. 20, and ends the second smoothing process (step S3).

Next, the CPU 511 proceeds to step S4, where the data obtained as a result of the second smoothing process is
The data is transferred to the binary image reproducing unit 53 via the CPU 15 and the series of processes shown in FIG. 18 is completed.

The binary image reproducing unit 53 shown in FIG.
Based on the second smoothed contour data transferred via the I / O 515, a binary image generated by filling an area surrounded by a vector graphic represented by the contour data is output in a raster scanning format. can do.

The outline of the outline scaling unit 5 has been described above. Here, in consideration of the erroneous determination of the image area determination unit 2, for a loop whose number of vectors is equal to or less than a certain threshold, a scaled image having better image quality can be obtained unless the second smoothing is performed, as in the case of the corner point. May be obtained.

Next, the pseudo halftone scaling unit 6 shown in FIG. 1 will be described. The scaling unit 6 outputs the output 1 of the binary image acquisition unit 1.
1 is input and an image is output at a desired magnification (the same magnification as that used in the outline magnification unit) by a magnification method different from the outline magnification.

The outline of the pseudo halftone scaling unit 6 will be described with reference to FIG.

Reference numeral 61 denotes an inverse quantization unit for temporarily restoring a binary image into a multi-valued image. As shown in FIG. 23, the inverse quantization processing unit 61 refers to, for example, the neighboring pixels of the 16 pixels around the pixel of interest 601 to calculate the product of each of the 16 pixels and each of the corresponding 16 coefficients. The sum is calculated, and the target pixel 601 is used as a multi-valued pixel value to be temporarily restored using the result. Next, the output of the inverse quantization processing unit 61, that is, the multi-valued pixel data is subjected to scaling processing in the SPC scaling processing unit 62 at a desired magnification (the same magnification as that used in the outline scaling unit). The SPC scaling process executed here is a well-known scaling process in which the same input pixel value is repeatedly output for enlargement by the number of times corresponding to the magnification, and the pixel is thinned out for reduction and output. is there.

The SPC scaled multi-valued pixel data is again binarized in the pseudo halftone processing unit 63 to obtain scaled binary image data. The pseudo halftone processing unit 63
For example, a known error diffusion processing circuit or a dither processing circuit is used.

The output 17 of the pseudo halftone processing section 63 thus obtained is used as the output of the pseudo halftone scaling section 6.

Here, the coefficient matrix in the inverse quantization processing section 61 of the pseudo halftone scaling section 6 does not necessarily need to be limited to the 4 × 4 size described in FIG.
In general, 8 × 8, 5 × 5, or 6 × 4 may be set as m × n (m and n are integers), and all the coefficients are not limited to “1”. Each element may have a different coefficient value, such as increasing the coefficient value closer to the target pixel as shown in FIG. If the size of the coefficient matrix matches the number of gradations of the pseudo-halftone representation of the original image, a faithful reproduction of a multi-valued image can be expected. It is desirable to do.

Next, in the selection / synthesis unit 7 of FIG. 1, the output 16 of the outline scaling unit 5 and the output 17 of the pseudo halftone scaling unit 6 are based on the output 14 of the image area determination result scaling unit 3. Selected and synthesized.

FIG. 26 is a block diagram showing the structure of the selection / synthesis unit 7. As shown in FIG.

Reference numeral 72 denotes a scaled image area determination result buffer for holding a scaled image area determination result (binary image data having the determination result as a pixel value) obtained from the image area determination result scaling unit 3. It is. Reference numeral 73 denotes an outline-scaled image data buffer for holding scaled binary image data obtained from the outline scaling unit 5. Reference numeral 74 denotes a pseudo halftone scaled image data buffer for holding scaled binary image data obtained from the pseudo halftone scaling unit 6.
Reference numeral 76 denotes a combined image data buffer for temporarily storing image data obtained by selectively combining the image data of the image data buffers 73 and 74. Reference numeral 71 denotes a raster scan format of the scaled image area determination result stored in the buffer 72, the outline scaled image data stored in the buffer 73, and the pseudo halftone scaled image data stored in the buffer 74. Is a synchronous control circuit that performs synchronous control so as to read data. The buffer 73 and the buffer 74 are controlled by the synchronization control circuit 71.
The scaled image data read in the raster scanning format is selectively synthesized for each pixel corresponding to each other, based on the scaled image area determination result read in the raster scanning format, and the synthesized image is obtained. The image is a composite image data buffer 7
6 is temporarily stored. The selection and synthesis of the image data after the scaling processing is performed by the logic circuit 75. That is, when the scaled image area determination result is 1 (indicating the pseudo halftone component), the pseudo halftone scaled image data is selected, and the scaled image area determination result is 0.
In the case of (character / line drawing component), outline resized image data is selected.

Finally, the binary image output unit 8 in FIG. 1 is synthesized by the selection / synthesis unit 7, and the synthesized image data buffer 76
A hard copy device, such as a laser beam printer or a thermal printer, for inputting the scaled image stored in the printer, or a display device, such as a liquid crystal display or a CRT, displays binary image data. Is recorded and output on paper.

[Second Embodiment] The binary image acquisition unit 1 in the first embodiment does not necessarily need to be an image reader, and may be, for example, a receiving unit of a facsimile apparatus.
It may be a binary image receiving device that inputs a binary image from outside the device via the communication unit. Also, the binary image output unit 8 in the first embodiment need not necessarily be a hard copy device. For example, a binary image (of course, encoded) using a communication unit like a transmission unit of a facsimile machine. May be output to the outside of the apparatus.
Further, the binary image output unit 8 may be an interface device for inputting a binary image from an external storage device such as a magnetic disk.

[Third Embodiment] In addition to the configuration of the first embodiment, the present invention can be realized by an apparatus having a configuration as shown in FIG. That is, the input of the outline scaling unit 5 in the first embodiment can be realized by a configuration in which the output 10 of the binary image acquisition unit 1 is directly input instead of the output of the outline extraction image generation unit 4. is there. In this case, the first
Although the memory capacity and processing time required by the outline scaling unit 5 may be increased as compared with the embodiment, the outline extraction image creating unit 4 is not required, and therefore, the outline scaling unit 5 and the other units may be used. There is an advantage that the device configuration can be simplified and the processing speed can be improved. In particular, this is effective for a device that targets an image with a small pseudo halftone component.

[Fourth Embodiment] The selective combining section 7 in the first embodiment shown in FIG. 26 described above can also be realized by the configuration shown in FIG.

That is, it is possible to reduce the number of buffers by sharing the pseudo halftone scaled image data buffer 74 and the composite image data buffer 76 shown in FIG.

Referring to FIG. 28, selective write circuit 77
Is based on the image area determination result output from the scaled image area determination result data buffer 72, and outputs the pseudo-intermediate output of the outline scaled image data buffer 73 only when the pixel is determined to be a character / line drawing component. The process of writing to the buffer 78 for both adjusted and scaled image data and the composite image data is performed in a raster scanning format. In this case, as compared with the first embodiment, a circuit for performing selective synthesis (selective writing circuit 7) is used.
Although the configuration of 7) is complicated, there is an effect that the number of necessary buffers can be reduced by one.

The scaling process performed by the pseudo halftone scaling unit 6 in the embodiment described above is described in, for example, Nikkei Electronics 1992, 5, 25 (No. 555) pp. 20
Mean density preservation method (MD method) introduced in 7-210
It may be.

The pseudo halftone scaling unit 6 scales the input image as binary image data by SPC processing without temporarily dequantizing the input image into a multivalued image.
The binary data obtained as a result of the processing may be configured to be output from the pseudo halftone scaling unit 6.

In this case, the configuration of such a portion is simplified, and there is an advantage that moderate image quality can be realized at low cost.

The present invention may be applied to a system constituted by a plurality of devices or to an apparatus constituted by one device. The present invention can also be applied to a case where the present invention is achieved by supplying a program for implementing the present invention to a system or an apparatus.

Therefore, it is needless to say that, for example, a scanner device for reading an original image, a host computer for processing the read image data, and a printer for forming the output image can be used. Further, the present invention can also be applied to a facsimile apparatus which receives an image, processes the input image according to the present embodiment, and outputs the processed image.

The original reason for performing the scaling process in the embodiment includes literally enlargement and reduction of the image.
For example, when the resolution of the image input from the binary image acquisition unit 1 and the output resolution of the binary image output unit 8 are different, the image processing is also used for processing for equalizing the image size between these images (resolution conversion processing). Can be

As described above, according to this embodiment, when the image is scaled by performing appropriate scaling processing on each of the character / line drawing component and the pseudo halftone component, a character・ Applying appropriate scaling processing to the line drawing component and appropriate scaling processing to the pseudo-halftone component to create two images, and then selecting and combining the images by image area determination, the character / line drawing component and Even in the case where an erroneous determination occurs in the pseudo halftone component, it is possible to obtain a scaled image of good image quality.

Further, according to the present embodiment, the black pixels to be input to the scaling process suitable for the character / line drawing component are limited to the black pixel determined to be the character / line drawing component and the black pixels around the black pixel. There is an effect that the required memory capacity and processing time are not increased while performing the scaling process.

[0088]

As described above, according to the present invention, it is possible to obtain a scaled image having good image quality even when an erroneous determination occurs between a character / line drawing component and a pseudo halftone component.

Further, according to the present invention, the input image is subjected to an appropriate scaling process for the character / line image component and an appropriate scaling process for the pseudo halftone component to create two images, and By selecting and combining two images based on the determination, there is an effect that a high-quality zoomed image can be obtained.

According to the present invention, the black pixels in the input to the scaling process suitable for the character / line drawing component are limited to the black pixel determined to be the character / line drawing component and the black pixels around the black pixel. There is an effect that it is possible to suppress an increase in required memory capacity and processing time while performing processing.

[0091]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an image area determination unit according to the present exemplary embodiment.

FIG. 3 is a diagram illustrating processing performed by a data holding unit and a synchronization determining unit of the image area determining unit according to the embodiment.

FIG. 4 is a diagram illustrating a configuration of a data holding unit of an image area determination unit according to the present embodiment.

FIG. 5 is a diagram illustrating an isolated center pixel determination process in image area determination.

FIG. 6 is a diagram illustrating an isolated pixel determination process in image area determination.

FIG. 7 is a diagram illustrating an area referred to in determining an isolated pixel in image area determination.

FIG. 8 is a diagram illustrating the content of a determination process of a high frequency component in image area determination.

FIG. 9 is a block diagram illustrating a configuration of an outline extraction image creating unit according to the present embodiment.

FIG. 10 is a diagram for explaining processing performed by a data holding unit of the outline extraction image creating unit;

FIG. 11 is a block diagram illustrating a configuration of an outline scaling unit of the present embodiment.

FIG. 12 is a diagram illustrating extraction of a rough contour vector from a raster scanning binary image.

FIG. 13 is a diagram illustrating extraction of a rough contour vector from a raster scanning type binary image.

FIG. 14 is a diagram illustrating extraction of a rough contour vector from a raster scanning type binary image.

FIG. 15 is a diagram illustrating a coarse contour vector output from an outline extraction unit according to the embodiment.

FIG. 16 is a block diagram illustrating a configuration of an outline smoothing / magnifying unit according to the embodiment.

FIG. 17 is a diagram illustrating a specific configuration example of an outline smoothing / magnifying unit according to the embodiment.

FIG. 18 is a flowchart illustrating an outline of outline smoothing / magnification processing according to the embodiment.

FIG. 19 is a diagram illustrating a processing operation of first smoothing.

FIG. 20 is a diagram illustrating contour data after second smoothing.

FIG. 21 is a diagram illustrating second smoothing.

FIG. 22 is a block diagram illustrating a configuration of a pseudo halftone magnification unit according to the embodiment.

FIG. 23 is a diagram illustrating the inverse quantization processing in the pseudo halftone scaling unit.

FIG. 24 is a diagram illustrating the inverse quantization processing in the pseudo halftone scaling unit.

FIG. 25 is a diagram illustrating the inverse quantization processing in the pseudo halftone scaling unit.

FIG. 26 is a block diagram illustrating a configuration of a selective combining unit according to an embodiment.

FIG. 27 is a block diagram illustrating a configuration of an image processing apparatus according to a second embodiment of the present invention.

FIG. 28 is a block diagram illustrating a configuration of a selective combining unit according to a fourth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 binary image acquisition unit 2 image area determination unit 3 image area determination result scaling unit 4 outline extraction image creation unit 5 outline scaling unit 6 pseudo halftone scaling unit 7 selective synthesis unit 8 binary image output unit 21 data Holding unit 22 Image area determination condition unit 27 Isolated pixel determination unit 28 Periodicity determination unit 29 High frequency component determination unit 54 Magnification setting unit 55 First smoothing / magnifying unit 56 Second smoothing unit 61 Inverse quantization processing unit 62 SPC Variable magnification processing section 63 Pseudo halftone processing section 510 Outline extraction circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-176162 (JP, A) JP-A-62-256055 (JP, A) JP-A-3-57083 (JP, A) JP-A-5-17683 211602 (JP, A) JP-A-63-35071 (JP, A) JP-A-2-9268 (JP, A) JP-A-4-101564 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) G06T 3/40 G06T 5/00 H04N 1/393

Claims (18)

(57) [Claims] 1. An image processing method comprising the steps of:
Torch, scale the extracted contour vector, and scale
First scaling means for generating scaled image data based on the obtained outline vector, and the first scaling means based on the input binary image data.
A second scaling unit for generating scaled image data by a different method, and a pseudo halftone area based on the input binary image data.
Image area determining means for determining whether the pixel is a pixel or a pixel in a character line drawing area, and determining that the pixel is not an isolated point based on the input binary image data
Of the pixel of interest, and one or more of the pixels surrounding the pixel of interest.
The upper pixel is a character / line drawing component, and the pixel of interest is
If the pixel is a black pixel, the image data of the pixel of interest is black.
Outputs binary image data indicating pixels to the first scaling unit
The outline extraction image creating means to be executed and the image area determination means
Select the scaled image data output from the first scaler
And if it is determined that the area is a pseudo halftone area, the second variable power means
Select the scaled image data output from the
The image processing apparatus characterized by comprising: a selective combining means for outputting as data, the. 2. The image processing apparatus according to claim 1, wherein the first and second scaling units change the magnification at an arbitrary magnification. 3. An isolated pixel determining unit that determines whether a pixel of interest is an isolated pixel, and an isolated pixel region determining unit that determines whether the pixel of interest is in an isolated pixel region. Periodicity determining means for determining whether the pixel value of a peripheral pixel of the target pixel is the same in a predetermined pixel cycle,
High-frequency component determining means for determining whether or not a density change frequently occurs between adjacent pixels, the isolated pixel determining means, the isolated pixel area determining means, the periodicity determining means, and the high-frequency component determining means. 2. The image processing apparatus according to claim 1, wherein it is determined whether the target pixel is in a character / line drawing area or a pseudo halftone area based on the determination result. 4. The first scaling unit includes: a contour vector extracting unit that extracts contour vector data along an edge of a given binary image; a smoothing unit that smoothes the extracted contour vector; Means for scaling the coordinate data constituting the smoothed vector data, drawing an outline based on the scaled coordinate data, and filling the outline with dots. Item 2. The image processing device according to Item 1. 5. The image processing apparatus according to claim 4, wherein said smoothing means changes a degree of smoothing according to a length of each contour vector extracted by said contour vector extracting means. 6. The multi-level converting means for multi-leveling a pixel of interest based on a pixel of interest in a given binary image and a group of binary pixels in the vicinity of the pixel of interest. When,
2. The image processing apparatus according to claim 1, further comprising: a binarizing unit that binarizes the multi-valued pixel data provided by the multi-level converting unit again using pseudo halftone expression. 7. The image combining device according to claim 1, wherein the selecting and combining unit includes:
The first and second scaling means based on the determination result by
2. The image processing apparatus according to claim 1, wherein the image processing apparatus selects and synthesizes each of the pixels scaled by each of the steps. 8. A result of the judgment by the image area judging means is shown.
A third scaling means for scaling the binary image;
Generating means for converting the result of the scaling by the third scaling means;
Based on the scaled image data output from the first scaler.
Data and a scaled image output from the second scaling means
The image processing apparatus according to claim 1, wherein any one of the scaled image data is selected . 9. The image processing apparatus according to claim 1, further comprising an output unit that outputs a binary image synthesized by the selection synthesis unit. 10. The image processing apparatus according to claim 9, wherein the output unit is a communication unit that encodes the binary image synthesized by the selection synthesis unit and outputs the encoded binary image via a line. 11. An image extracted from input binary image data.
Scales the scaled contour vector to a scaled contour vector.
A first scaling step of generating scaled image data based on the input image data;
A second scaling step of generating scaled image data by a different method, and a pseudo halftone area based on the input binary image data.
An image area determining step of determining whether the pixel is a pixel or a pixel in a character / line drawing area, and determining that the pixel is not an isolated point based on the input binary image data
Of the pixel of interest, and one or more of the pixels surrounding the pixel of interest.
The upper pixel is a character / line drawing component, and the pixel of interest is
If the pixel is a black pixel, the image data of the pixel of interest is black.
Outputting binary image data indicating pixels to the first scaling step;
An outline extraction image creating step to be performed, and the image area determination step
Select the scaled image data output in the first scaling step.
And if it is determined that the area is a pseudo halftone area, the second variable magnification
Select the scaled image data output according to the process
An image processing method , comprising: selecting and synthesizing the data as data . 12. The image processing method according to claim 11, wherein the magnification in the first and second magnification steps can be set to an arbitrary value. 13. The image area determining step includes: an isolated center pixel determining step of determining whether the pixel of interest is an isolated pixel; and an isolated pixel area determining step of determining whether the pixel of interest is in an isolated pixel area. A periodicity determining step of determining whether a pixel value is the same in a predetermined pixel cycle, and a high-frequency component determining step of determining whether a density change frequently occurs between adjacent pixels, It is determined whether the pixel of interest is in the character line drawing area or the pseudo halftone area based on the determination results of the isolated pixel area determination step, the periodicity determination step, and the high frequency component determination step in the isolated center pixel determination step. The image processing method according to claim 11, wherein: 14. The method according to claim 1, wherein the first zooming step includes a step of:
A contour vector extracting step of extracting contour vector data along the edge of the value image, a smoothing step of smoothing the extracted contour vector, and scaling of coordinate data constituting the smoothed vector data. 12. The image processing method according to claim 11, further comprising: drawing an outline based on the coordinate data after scaling, and filling the outline with dots. 15. The image processing method according to claim 14, wherein in the smoothing step, a degree of smoothing is changed according to a length of each contour vector extracted in the contour vector extracting step. 16. The method according to claim 16, wherein the second zooming step includes a step of:
A multi-value process for multi-leveling the pixel of interest based on the pixel of interest in the value image and the binary pixel group near the pixel of interest; 12. The image processing method according to claim 11, further comprising a binarization step of performing binarization in a tone expression. 17. The method according to claim 17, wherein in the selective combining step, the image area determination is performed.
The first and second magnifications based on the determination result of the process
12. The image processing method according to claim 11, wherein each of the pixels scaled by the step is selected and synthesized. 18. A determination result in the image area determination step.
A third scaling step of scaling the binary image shown,
In the selective combining step, the result of scaling in the third scaling step is
Based on the variable magnification image output by the first magnification step
Image data and a scaling output in the second scaling step.
The image processing method according to claim 11, wherein the this <br/> for selecting one of the scaled image data magnification image data.