JPH0799575A - Processing method for picture information - Google Patents

Abstract

PURPOSE:To provide an excellent picture when the density of the picture information after magnification is corrected by setting a correction density respectively lower or higher depending whether the density of magnified picture information between adjacent picture elements is steep or slow. CONSTITUTION:Main scanning and sub scanning are conducted sequentially to an original set to a scanner section 1. A magnification section 2 magnifies picture information. When an MTF correction section 3 conducts the MTF correction, the section 2 sets the correction lower when a density change between adjacent picture elements of magnified picture information is steep and the section 2 sets the correction higher when the density change slows down. The picture information is binarized by a binarization section 4, a plotter section 5 records a picture or a transmission section 6 is used to send the picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various image processing apparatuses, in which multi-gradation image information is scaled as necessary and then MT
F (Modulation Transfer Fun)
The present invention relates to a method of processing image information when executing correction or smoothing processing.

[0002]

2. Description of the Related Art In various image processing apparatuses, a manuscript image is read at a constant resolution, the obtained multi-gradation image information is scaled as needed, and the scaled image information is corrected. Two
A series of image processing of digitizing is often executed. The scaling is a process of enlarging or reducing an image by increasing or decreasing the number of pixels of image information in the main scanning direction and the sub scanning direction.

The nearest neighbor method and the linear interpolation method are well known as methods of this scaling processing. A method in which these processing methods are applied to one of the main scanning direction and the sub-scanning direction of image information is called a one-dimensional nearest neighbor method or a one-dimensional linear interpolation method. It is called a two-dimensional nearest neighbor method or a two-dimensional linear interpolation method.

In the nearest neighbor method, the density of each pixel after scaling is set to the density of the closest one pixel on the image information before scaling. For this reason, the nearest neighbor method is simple in processing and easy in high-speed processing, but on the other hand, the density change between the adjacent pixels of the obtained image information becomes sharp, resulting in a slightly unnatural image.

Further, in the linear interpolation method, each pixel density after scaling is set to another new density calculated based on the densities of a plurality of pixels located at close positions on the image information before scaling. Therefore, contrary to the above, the linear interpolation method requires complicated processing and long processing time, but the obtained image information has a gradual change in density between adjacent pixels and a natural image can be obtained.

In addition to such a scaling method, in general, when enlarging image information, the larger the magnification, the more the fixed area is represented by a large number of pixels.
The density change between adjacent pixels becomes gentle.

As described above, the density change between pixels becomes steep or gradual depending on the difference in the magnification changing method and the magnification change.

On the other hand, as a method of correcting image information in the series of image processing, there are MTF correction and smoothing, for example. Further, as a method of binarizing the corrected image information, a simple binarization in which the pixel density is compared with a fixed threshold value and binarized,
There are pseudo halftone binarization such as dither processing and error diffusion processing.

Generally, image information obtained by reading a text original is simply binarized after MTF correction. MT
The F correction is a process of correcting the pixel density so that the density difference between the pixels becomes larger and emphasizing the shading of the image. By this processing, the outline of the character image can be clarified.

Further, image information obtained by reading a light and dark original such as a picture or a photograph is smoothed and then binarized by pseudo halftone. Contrary to the MTF correction, the smoothing is a correction process that suppresses the density change so that the density difference between pixels becomes smaller. By this processing, it is possible to prevent the image quality from deteriorating due to the occurrence of moire in the image binarized with the pseudo halftone.

By the way, when executing the scaling processing of image information, for example, when prioritizing high-speed processing over image quality,
When the nearest neighbor method is used and the image quality is prioritized over the processing time, there are cases where the two scaling processing methods are selectively used, such as the linear interpolation method.

In this case, conventionally, irrespective of the scaling method and scaling ratio used, when the scaling-processed image information is corrected by MTF correction or smoothing, it is always corrected with a constant correction degree. It was This is because the scaling factor is "1", that is,
The same was true when the magnification was not changed.

For this reason, for example, when MTF correction is performed on image information that has been subjected to scaling processing by the nearest neighbor method, image information whose density change is sharp due to scaling processing is further emphasized by MTF correction. The image quality sometimes deteriorated. Further, when MTF correction of image information enlarged at a high magnification by the linear interpolation method is performed, the density change between pixels is moderated by the magnification processing, and thus the emphasis by the MTF correction is insufficient and a clear image can be obtained. There was nothing.

Further, for example, in the case of smoothing the image information which has been subjected to the scaling processing by the nearest neighbor method, the density change is steep due to the scaling processing, and therefore the density change cannot be sufficiently suppressed by the smoothing. , Moire may occur in the obtained image. Also. When the image information enlarged at a high magnification is smoothed by the linear interpolation method, the image information whose density change is gentle is changed to a more gentle density change, and a clear image cannot be obtained.

[0015]

As described above, the prior art is as follows.
There is a problem that it is not possible to execute an appropriate correction process suitable for the property of image information, and the image quality of the processed image may deteriorate.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and provide a method of processing image information which can always perform an appropriate correction process to obtain a good image.

[0017]

Therefore, in one invention of the present application, when the density change between adjacent pixels of the scaled image information is sharp, the correction degree of the MTF correction is set low, while When the density change is gradual, the correction degree is set high.

According to another aspect of the invention, when the density change between adjacent pixels of the scaled image information is sharp, the correction degree of the smoothing process is set low, while when the density change is gentle. , The correction degree is set high.

[0019]

As a result, the MTF correction or smoothing of the image information can always be appropriately executed to obtain a good image.

[0020]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the arrangement of an image processing apparatus according to the first embodiment of the present invention. In the figure, a scanner unit 1 reads a document image and extracts multi-tone image information. The scaling unit 2 has two scaling processing functions, a two-dimensional nearest neighbor method and a two-dimensional linear interpolation method, and scales image information by one of the scaling processing functions. The MTF correction unit 3 performs MTF correction on image information by increasing the density difference between pixels and emphasizing shading. The binarization unit 4 binarizes multi-tone image information into black and white image information. Plotter part 5
Is for recording and outputting an image. The transmission unit 6 transmits an image to another device by a facsimile communication procedure.

When the image processing apparatus of the present embodiment is operated with the above-mentioned configuration, the operator sets a document on the scanner section 1 and designates a scaling processing method with an operation section (not shown).
Start the device. The scaling processing methods are the two-dimensional nearest neighbor method and the two-dimensional
It is specified by selecting one of the dimensional linear interpolation methods. This designation information is input to the scaling unit 2 and the MTF correction unit 3.

It is assumed that the image processing apparatus is activated now. Then, the scanner unit 1 sequentially executes the main scanning and the sub-scanning on the set document to read the image information.
This image information is multi-tone image information that represents the shade of the original image. The scaling unit 2 scales the image size at a constant magnification by increasing or decreasing the number of pixels of the image information read by the scanner unit 1 in the main scanning direction and the sub scanning direction. At this time, each pixel density of the scaled image information is set by a predetermined method according to the scaling processing method. In the present embodiment, the scaling factor is set in advance.

Now, as shown in FIG. 2, in the image information before scaling, four adjacent pixels are represented by f (m,
n), f (m + 1, n), f (m + 1, n) and f
(M + 1, n + 1) and 2 surrounded by these 4 pixels
Consider a dimensional coordinate area. When one pixel of interest after scaling is g (x, y), the pixel of interest g (x,
It is assumed that y) is located at the coordinates i, j in the two-dimensional coordinate area. The coordinates i and j are represented by "0 to 1", where the vertical and horizontal distances of the coordinate area are "1".

When the two-dimensional nearest neighbor method is specified, each pixel density is set as follows. That is, when the scaling unit 2 focuses on one pixel after scaling, as shown in FIG. 3, the scaling unit 2 determines the coordinates i, j of the target pixel g (x, y) (process 101). The coordinates i and j are both “0.5”.
In the following cases (Y in process 101), the pixel of interest g (x, y)
Is set to the density of the pixel f (m, n) of the original image information before scaling (process 102).

Further, the coordinate i exceeds "0.5", and the coordinate j
Is less than or equal to “0.5” (from N in process 101 to process 10
3, Y of processing 103), the density of the target pixel g (x, y) is set to the density of the pixel f (m + 1, n) (processing 10).
4).

If the coordinate i is "0.5" or less, the coordinate j
Is more than “0.5” (process 103 from process 103)
05, Y in processing 105), the density of the pixel of interest g (x, y) is set to the density of the pixel f (m, n + 1) (processing 10).
6).

Further, when both the coordinates i and j exceed "0.5" (process 107, process 107 from N of process 105)
Y) of the target pixel g (x, y)
The density is set to (1, n + 1) (process 108).

As a method of scaling the image information, in each of the main scanning direction and the sub-scanning direction, pixels are simply thinned out at a fixed number of pixels to be reduced, or pixels having the same density as that of an adjacent pixel. There is a method of interpolating and expanding. These processes are also included in the two-dimensional nearest neighbor method.

On the other hand, when the two-dimensional linear interpolation method is specified, the scaling unit 2 determines the target pixel g (x, y) after scaling.
The concentration of is set by the following formula. g (x, y) = (1-i) * (1-j) * f (m, n) + i * (1-j) * f (m + 1, n) + (1-i) * j * f ( m, n + 1) + ijf (m + 1, n + 1)

The scaling unit 2 outputs the image information scaled by the above various scaling processing methods. The MTF correction unit 3 performs MTF correction on the image information.

In this MTF correction, attention is sequentially paid to each area of vertical and horizontal 3 pixels of image information, a correction coefficient is set to each pixel at a fixed position in the attention area, and the central pixel is subjected to density based on the correction coefficient. This is a correction process.

That is, here, as shown in FIG. 4, when each pixel of the attention area is A to I, five pixels B, D, E, F, and H among them are shown in FIG. , The correction coefficients b, d, e, f, h are set respectively. And
The central pixel E of the attention area is corrected to the density E ′ by the following equation. E ′ = e · E−b · B−d · D−f · F−h · H

In this embodiment, the correction coefficients b, d, f,
As shown in FIG. 6, h is "-0.5" when the scaling processing method is the two-dimensional nearest neighbor method and "-0.5" when the scaling processing method is the two-dimensional linear interpolation method.
1 "respectively. The correction coefficient e is set to "3" in the former case and "5" in the latter case. It is necessary to set the total value of the five correction coefficients to always be "+1".

The MTF correction unit 3 executes such density correction according to the designated scaling processing method. As a result, the central pixel E of the attention area is corrected so that the density difference becomes larger than that of the four adjacent pixels, and the central pixel E is emphasized.

The binarizing unit 4 binarizes the black and white image information by a simple binarizing method of comparing each pixel density of the image information thus corrected with a fixed threshold value.

It is assumed that it is preset whether only one of the plotter unit 5 and the transmitting unit 6 is operated or both of them are operated. When the plotter unit 5 is set to operate, the plotter unit 5 records and outputs the binarized image information. When the transmission unit 6 is set to operate, the transmission unit 6 transmits the image information to another device.

As described above, in the present embodiment, the correction coefficients b, d, f, and h for MTF correction are set to a small negative value when the scaling processing method is the two-dimensional nearest neighbor method. In the case of the linear interpolation method, a large negative value is set. The correction coefficient e is set to a constant value determined by the correction coefficients b, d, f, and h.

As the correction coefficients b, d, f, and h increase in the negative direction, the degree of correction increases, and the pixel E becomes more emphasized.

In the case of the two-dimensional nearest neighbor method, the pixel density of the original image information before scaling is set as it is to the pixel density of the new image information after scaling as described with reference to FIG. The concentration change between pixels becomes sharp. In this embodiment, in this case, the correction coefficients b, d, f, and h are set to small values, so the correction degree becomes low. As a result, it is possible to obtain an appropriately emphasized good image without overemphasizing the image information that originally has a sharp change in density.

On the other hand, in the case of the two-dimensional linear interpolation method, since a new density is calculated from the densities of the four pixels of the original image information,
The density change between adjacent pixels becomes gentle. In this case, since the correction coefficients b, d, f, h are set to large values, the correction degree becomes high. As a result, the contour portion of the image can be appropriately clarified, and a good image can be obtained.

Next, an image processing apparatus according to the second embodiment of the present invention will be described.

The image processing apparatus of this embodiment has the same structure as that of FIG. However, when the operator starts the device,
A scaling process method and a scaling factor are designated. As shown in FIG. 7, the scaling processing method and the designation information of the scaling ratio include the scaling unit 2 and the MT.
It is input to the F correction unit 3.

It is assumed that the image processing apparatus is activated now. Then, the scanner unit 1 reads the document image and extracts the image information, and the scaling unit 2 scales the image information under the set conditions. Then, the MTF correction unit 3 performs MTF correction on the scaled image information.

In this embodiment, at the time of this MTF correction, the correction coefficient is set as shown in FIG. That is, when the set scaling ratio is less than 150% and the two-dimensional nearest neighbor method is specified, the correction coefficients b, d, f, and h are set to "-0.
5 "and the correction coefficient e are set to" 3 ", respectively. Also,
When the two-dimensional linear interpolation method is designated with the same scaling factor, the correction coefficients b, d, f, and h are set to "-1" and the correction coefficient e is set to "5". On the other hand, if the scaling factor is 150% or more and the two-dimensional nearest neighbor method is used, set the same value as above,
In the case of the two-dimensional linear interpolation method, the correction coefficients b, d, f, h
Is set to "-1.5" and the correction coefficient e is set to "7".

The MTF correction section 3 performs MTF correction on image information with such a correction coefficient. Then, as in the above-described embodiment, the corrected image information is binarized, and the obtained image is recorded or transmitted.

As described above, in the present embodiment, when the scaling processing method is the same and the scaling factor is large, the correction coefficient b,
d, f, and h are set to large negative values.

As the scaling ratio increases, a certain area of the image is represented by a large number of pixels, so the density change between adjacent pixels becomes gentle. Therefore, in this case, since the correction coefficient is increased to increase the degree of correction of the MTF correction, the contour portion of the image is further emphasized and a clear image can be obtained.

When the scaling factors are the same, the correction coefficients b, d, f, and h are small in the two-dimensional nearest neighbor method and large in the two-dimensional linear interpolation method, as in the above-described embodiment. It is set to each value. As a result, it is possible to prevent overcorrection and undercorrection due to the difference in the scaling processing method, and always obtain a good image.

Next, an image processing apparatus according to the third embodiment of the present invention will be described.

FIG. 9 is a block diagram of the image processing apparatus of this embodiment, and the same reference numerals as those in FIG. 1 denote the same parts. In the figure, a main scanning direction scaling unit 7 scales image information in the main scanning direction by a one-dimensional linear interpolation method. The sub-scanning direction scaling unit 8 scales the image information in the sub-scanning direction by the one-dimensional nearest neighbor method. Switch 9
Is to switch the signal path depending on whether the scaling process is executed or not.

With the above-mentioned configuration, in this embodiment, the operator arbitrarily specifies whether or not to execute the scaling process when starting the apparatus.

The designation information is input to the switch 9 and the MTF correction unit 3. When the scaling process is not executed, the image information read by the scanner unit 1 is directly input to the MTF correction unit 3 via the switch 9. Further, when performing the scaling process, the main scanning direction scaling unit 7 scales the image information output from the scanner unit 1 in the main scanning direction at a constant scale by a one-dimensional linear interpolation method.

Here, as shown in FIG. 10, two adjacent pixels of the original image information before scaling are represented by f (m) and f (m
+1). In addition, g
(X), and the coordinate of the target pixel g (x, y) is i. It should be noted that this coordinate i is the same as the above two pixels f (m) and f
It is assumed that the distance between (m + 1) is "1" and is represented by "0 to 1".

In this case, the main scanning direction scaling unit 7 sets the density of the target pixel g (x) after scaling according to the following equation. g (x) = (1-i) * f (m, n) + i * f (m +
1)

The main scanning direction scaling section 7 sets the density in this way when scaling the image information in the main scanning direction.

The sub-scanning direction scaling unit 8 scales the image information in the sub-scanning direction by the one-dimensional nearest neighbor method. FIG. 11 shows a method of setting the density of the target pixel g (x) in this case. That is, the sub-scanning direction scaling unit 8 determines the coordinate i (process 201), and if the coordinate i is 0.5 or less (process 2).
01), and the density of the pixel f (m) is set to the density of the target pixel g (x) (process 202). On the other hand, the coordinate i is 0.5
If it exceeds (Y in processing 203), the pixel f (m + 1)
Is set to the density of the target pixel g (x) (process 20).
4). The sub-scanning direction scaling unit 8 sets the density in this way when scaling the image information in the sub-scanning direction.

When the scaling of the image information is instructed, the scaled image information is transmitted via the switch 9 to the MTF correction unit 3
Entered in.

The MTF correction section 3 executes MTF correction on the input image information. In this embodiment, this MTF
At the time of correction, the correction coefficient is set as shown in FIG. That is, when the scaling process is not designated, the correction coefficients b, d, f, and h are set to "-0.5" and the correction coefficient e is set to "3". On the other hand, when the scaling process is designated, the correction coefficients b and h are set to "-0.5", the correction coefficients d and f are set to "-1", and the correction coefficient e is set to "4".

The MTF correction section 3 performs MTF correction on image information with such a correction coefficient. Then, as in the above-described embodiment, the corrected image information is binarized, and the obtained image is recorded or transmitted.

As described above, in the present embodiment, when the scaling process is not executed, the correction coefficients b, d, f and h are all set to the same value of "-0.5". hand,
When executing the scaling process, only the correction coefficients d and f are “−1”.
Has been changed to a large negative value.

When performing the scaling processing, the main scanning direction scaling unit 7 performs the scaling processing by the one-dimensional linear interpolation method, so that the density change between pixels in the main scanning direction becomes gentle. On the other hand, in the sub-scanning direction scaling unit 8, since the scaling process is executed by the one-dimensional nearest neighbor method, the density change between pixels in the sub-scanning direction becomes sharp.

In this case, the correction coefficients d and f corresponding to the main scanning direction are set to large negative values, and the degree of correction in the main scanning direction becomes higher, so that the main scanning direction and the sub-scanning direction are respectively divided. It is properly emphasized and a good image is obtained.

Further, in this embodiment, the sub-scanning direction magnification changing unit 8
Performs a scaling process by the one-dimensional nearest neighbor method. When performing the scaling in the sub-scanning direction by the one-dimensional linear interpolation method, a memory for temporarily storing image information for at least three lines is required. On the other hand, in the case of scaling by the one-dimensional nearest neighbor method, since it can be executed if there is at least one line of memory, the hardware circuit can be easily configured.

Next explained is an image processing apparatus according to the fourth embodiment of the invention.

In the image processing apparatus of this embodiment, the switch 9 in the configuration shown in FIG. 9 is deleted, and as shown in FIG. 13, the image information output from the scanner section 1 is always supplied to the main scanning direction scaling section 7. It is processed by the sub-scanning direction scaling unit 8 to be processed by the MTF correction unit
I am trying to type in.

In this embodiment, the operator arbitrarily specifies the scaling factor when starting the apparatus. The specified information is
It is input to the main scanning direction scaling unit 7, the sub scanning direction scaling unit 8, and the MTF correction unit 3.

When the apparatus is activated, the scanner section 1 reads the original image, and the main scanning direction scaling section 7 and the sub scanning direction scaling section 8 scales the image information at the set scaling rate.

Then, the MTF correction unit 3 performs MTF correction on the scaled image information. In this embodiment, M
The correction coefficient for TF correction is set as shown in FIG. That is, when the set scaling ratio is less than 150%, the correction coefficients b and h are "-0.5", and the correction coefficients d and f are "-."
1 "and the correction coefficient e are set to" 4 ", respectively. on the other hand,
When the scaling factor is 150% or more, the correction factors b and h are set to "-
1 ", the correction coefficients d and f are set to" -1.5 ", and the correction coefficient e is set to" 6 ".

The MTF correction section 3 performs MTF correction on image information with such a correction coefficient. Then, after binarizing the corrected image information, the obtained image is recorded or transmitted.

As described above, in the present embodiment, the correction coefficients d and f in the main scanning direction are set to values larger than the correction coefficients b and h in the sub-scanning direction, as in the above-described embodiments.
When the scaling factor is large, those correction coefficients are set to be large as a whole.

As a result, the image can be appropriately emphasized in each of the main scanning direction and the sub-scanning direction, and the degree of the emphasis can be maintained even if the scaling ratio changes, which is always good. Images can be obtained.

Next explained is an image processing apparatus according to the fifth embodiment of the invention.

FIG. 15 shows the image processing apparatus of this embodiment, and the same reference numerals as those in FIG. 9 indicate the same parts. In the figure, the scanner unit 10 has a function of changing the sub-scanning pitch when reading a document image and scaling the image information to be taken out in the sub-scanning direction.

In this embodiment, the operator arbitrarily designates whether or not to execute the scaling process when starting the apparatus. This designation information is input to the scanner unit 10, the main scanning direction scaling unit 7, and the MTF correction unit 3.
It is assumed that the scaling factor for executing the scaling process is fixedly set in advance.

When the scaling process is not executed, the scanner section 10 scans the original image by sub-scanning at a predetermined standard pitch. When execution of the scaling process is designated, the original image is read by sub-scanning at a preset constant pitch. This fixed pitch is set to 1/2 of the standard pitch when the scaling ratio is 200%, and is set to twice the standard pitch when the scaling ratio is 50%.

When the scaling process is not executed, the main scanning direction scaling unit 7 inputs the image information read by the scanner unit 10 to the MTF correction unit 3 as it is. When executing the scaling process, the image information is scaled in the main scanning direction at the set scaling ratio and input to the MTF correction unit 3.

The MTF correction unit 3 executes MTF correction on the input image information. In this embodiment, the correction coefficient is set as shown in FIG. That is, when the scaling process is not executed, the correction coefficients b, d, f, and h are set to "-0.5",
The correction coefficient e is set to "3", respectively. On the other hand, when the scaling process is executed, the correction coefficients b and h are set to "-1", the correction coefficients d and f are set to "-0.5", and the correction coefficient e is set to "4".

The MTF correction section 3 performs MTF correction on image information with such a correction coefficient. Then, as in the above-described respective embodiments, the image information is binarized, and the obtained image is recorded or transmitted.

As described above, in the present embodiment, when the variable magnification processing is executed, the correction coefficients b and h in the sub-scanning direction are set to a negative value larger than the correction coefficients d and f in the main scanning direction. ing.

In this embodiment, the image information is scaled in the sub-scanning direction by changing the sub-scanning pitch of the scanner section 10. In general, image information that has been magnified by changing the scanning pitch has a gradual change in density between pixels, regardless of the magnitude of magnification, as compared to image information that has been magnified by the various magnification processing methods described above. Becomes

In this embodiment, when executing the scaling process,
Since the correction coefficients b and h in the sub-scanning direction are set to large negative values to emphasize more, a clear image can always be obtained.

Next explained is an image processing apparatus according to the sixth embodiment of the invention.

The image processing apparatus of this embodiment has the same configuration as that shown in FIG. And when starting the device,
The operator specifies a desired scaling factor. This designation information is input to the scanner unit 10, the main scanning direction magnification varying unit 7, and the MTF correcting unit 3, as shown in FIG.

The scanner section 10 reads a document image at a sub-scanning pitch corresponding to a designated scaling ratio and outputs image information of a predetermined size. The main scanning direction scaling unit 7 scales the image information in the main scanning direction at a designated scaling ratio. And MT
The F correction unit 3 performs MTF correction on the scaled image information.

In this embodiment, the correction coefficient is set as shown in FIG. That is, the set scaling factor is 150%
If less than, the correction factors b and h are “−1”, the correction factors d,
f is set to "-0.5" and the correction coefficient e is set to "4". On the other hand, when the scaling factor is 150% or more, the correction coefficients b and h are set to "-1.5", the correction coefficients d and f are set to "-1", and the correction coefficient e is set to "6".

The MTF correction section 3 performs MTF correction on image information with such a correction coefficient. Then, the corrected image information is set to 2
It digitizes and records or transmits the obtained image.

As described above, in the present embodiment, when the image information is scaled, the correction degree in the sub-scanning direction is set higher than that in the main scanning direction in the same manner as in the above-described embodiment, while the scaling rate increases. The degree of correction is further increased in both the sub-scanning direction and the main scanning direction.

As a result, when the scaling factor becomes large and the density change between pixels becomes gentle, the image is emphasized more, so that a clear image can always be obtained.

Next explained is an image processing apparatus according to the seventh embodiment of the invention.

FIG. 19 shows the image processing apparatus of this embodiment. In the figure, the difference from FIG. 1 is that the MTF correction units 3 and 2 are
Instead of the binarizing unit 4, the smoothing unit 11 and the halftone binarizing unit 12
Is provided.

The smoothing section 11 executes a smoothing process for suppressing the density change of image information. Halftone binarization unit 1
2 is for binarizing multi-valued image information by pseudo halftone processing.

With this configuration, in this embodiment, as in the embodiment of FIG. 1, the operator specifies the scaling processing method when starting the image processing apparatus. The designation information is input to the scaling unit 2 and the smoothing unit 11.

When the apparatus is activated, the scanner section 1 reads the image information, and the scaling section 2 scales the image information by the designated scaling processing method. The smoothing unit 11 smoothes the scaled image information.

In this smoothing processing, attention is paid to each area of vertical and horizontal 3 pixels of image information, a correction coefficient is set to each pixel at a fixed position in the attention area, and the central pixel is set based on the correction coefficient. This is a process for correcting the density.

That is, here, as in the case of the above-mentioned MTF correction, as shown in FIG.
~ I, the correction factors b, d, e, f, for five pixels B, D, E, F, H among them are shown in FIG.
Set h respectively. Then, the central pixel E of the attention area
Is corrected to the density E ′ by the following equation. E '= (e * E + b * B + d * D + f * F + h * H) /
8

In this embodiment, the correction coefficients b, d, f,
As shown in FIG. 20, h is set to "1.5" when the scaling processing method is the two-dimensional nearest neighbor method and "1.25" when the scaling processing method is the two-dimensional linear interpolation method. In addition, the correction coefficient e
Is set to "2" in the former case and "3" in the latter case.
It is necessary to set the total value of the five correction coefficients to be “8” at all times.

The smoothing section 11 executes such density correction according to the designated scaling processing method. This allows
The central pixel E of the attention area is corrected so that the difference in density between the four adjacent pixels becomes smaller.

The halftone binarization unit 12 binarizes each pixel density of the image information thus corrected into black and white image information by a known pseudo halftone process such as a dither method or an error diffusion method.

The binarized image information is sent to the plotter unit 5.
Is recorded and output, or is transmitted to another device by the transmission unit 6.

As described above, in the present embodiment, the correction coefficients b, d, f, and h of the smoothing process are set to a large value when the scaling process used is the two-dimensional nearest neighbor method, and 2 In the case of the dimensional linear interpolation method, it is set to a small value.

As the correction coefficients b, d, f, and h are set to a larger value, the degree of smoothing for reducing the gradation change of the image becomes stronger.

In the case of the two-dimensional nearest neighbor method, the concentration change between adjacent elements becomes steep, and in this case, the correction coefficients b, d,
By setting f and h to be large, it is possible to suppress a sharp change in density to an appropriate change. Generally, when image information having a large density change is binarized by a pseudo halftone process, moire occurs in the image and the image quality deteriorates. However, in the present embodiment, such image quality is reduced by appropriately suppressing the density change. It is possible to prevent deterioration.

On the other hand, in the case of the two-dimensional linear interpolation method, since the density change between adjacent pixels becomes gentle, the correction coefficients b, d,
By setting f and h to small values, it is possible to prevent the image from becoming unclear because the density does not change more than necessary.

Next explained is an image processing apparatus according to the eighth embodiment of the invention.

The image processing apparatus of this embodiment has the same structure as that of FIG. However, the operator specifies the scaling processing method and the scaling factor when starting the apparatus. As shown in FIG. 21, the scaling processing method and the designation information of the scaling ratio are used in the scaling unit 2
Is input to the smoothing unit 11.

When the apparatus is activated, the scanner section 1 reads a document image and outputs image information. The scaling unit 2 scales the image information under specified conditions. Then, the smoothing unit 11 smoothes the scaled image information.

In the present embodiment, the correction coefficient for this smoothing process is set as shown in FIG. That is, when the set scaling ratio is less than 150% and the scaling processing method is the two-dimensional nearest neighbor method, the correction coefficients b, d, f, and h are set to “1.5”,
The correction coefficient e is set to "2". In the case of the two-dimensional linear interpolation method with the same scaling factor, the correction coefficient b,
The d, f and h are set to "1.25" and the correction coefficient e is set to "3". On the other hand, in the case of the scaling factor of 150% or more and the two-dimensional nearest neighbor method, the same value as above is set, and in the case of the two-dimensional linear interpolation method, the correction coefficients b, d, f, and h are set to "1". , And the correction coefficient e is set to “4”.

The smoothing section 11 smoothes the image information with such a correction coefficient. Then, as in the above-described embodiment, the corrected image information is binarized, and the obtained image is recorded or transmitted.

As described above, in the present embodiment, when the scaling processing method is the same and the scaling factor is large, the correction coefficient b,
d, f, and h are set to small values.

As the scaling ratio increases, the density change between adjacent pixels becomes gentler. In this case, the correction coefficient is reduced to reduce the degree of smoothing, so that the shading of the image becomes unnecessarily small and an unclear image is prevented.

When the scaling factors are the same, the correction coefficients b, d, f, and h are large values in the two-dimensional nearest neighbor method and small values in the two-dimensional linear interpolation method, as in the above embodiment. Is set to. This makes it possible to carry out smoothing to the same degree with either scaling processing method, and always obtain a good image.

Next explained is an image processing apparatus according to the ninth embodiment of the invention.

FIG. 23 is a block diagram of the image processing apparatus of this embodiment, and the same reference numerals as those in FIG. 9 or 19 denote the same parts.

With this configuration, in this embodiment, the operator arbitrarily specifies whether or not to execute the scaling process when starting the apparatus.

The designation information includes the switch 9 and the smoothing unit 11.
Entered in and. When the scaling process is not executed, the image information read by the scanner unit 1 is directly input to the smoothing unit 11 via the switch 9.

When executing the scaling process, the main scanning direction scaling unit 7 uses the one-dimensional linear interpolation method to scan the scanner unit 1.
The image information output from is scaled in the main scanning direction at a constant magnification. Further, the sub-scanning direction scaling unit 8 further scales the image information scaled in the main scanning direction by a constant magnification in the sub scanning direction by the one-dimensional nearest neighbor method. The image information thus scaled is input to the smoothing unit 11.

The smoothing section 11 smoothes the input image information. In this embodiment, at this time, the correction coefficient for the smoothing process is set as shown in FIG. That is, when the scaling process is not executed, the correction coefficients b, d, f, and h are set to "1.
5 "and the correction coefficient e are set to" 2 ", respectively. on the other hand,
When executing the scaling process, the correction coefficients b and h are set to "1.
5 ", the correction coefficients d and f are set to" 1.25 ", and the correction coefficient e is set to" 2.5 ".

The smoothing section 11 smoothes the image information with such a correction coefficient. Then, as in the above-described embodiment, the corrected image information is binarized, and the obtained image is recorded or transmitted.

As described above, in the present embodiment, when the scaling processing is not executed, the correction coefficients b, d, f and h are all set to the same value of "1.5". When executing the scaling process, only the correction coefficients d and f are set to "1.2
It has been changed to a low value of 5 ".

When performing the scaling processing, the main scanning direction scaling unit 7 performs the scaling processing by the one-dimensional linear interpolation method, so that the density change between pixels in the main scanning direction becomes gentle. On the other hand, in the sub-scanning direction scaling unit 8, since the scaling process is executed by the one-dimensional nearest neighbor method, the density change between pixels in the sub-scanning direction becomes sharp.

In this case, the correction coefficients d and f corresponding to the main scanning direction are set to small values, and the degree of smoothing in the main scanning direction becomes low. Therefore, the main scanning direction and the sub-scanning direction each have a proper degree. Density changes are suppressed and good images are always obtained.

Next explained is an image processing apparatus according to the tenth embodiment of the invention.

In the image processing apparatus of this embodiment, the switch 9 having the configuration shown in FIG. 23 is deleted, and as shown in FIG. 25, the image information output from the scanner section 1 is always supplied to the main scanning direction scaling section 7.
And the sub-scanning direction scaling unit 8 to process the halftone binarization unit 12.
I am trying to type in.

In this embodiment, the operator arbitrarily specifies the scaling factor when starting the apparatus. The specified information is
Main scanning direction scaling unit 7, sub scanning direction scaling unit 8 and smoothing unit 11
Entered in and.

When the apparatus is activated, the scanner section 1 reads the original image, and the main scanning direction scaling section 7 and the sub scanning direction scaling section 8 scales the image information by the set scaling rate.

The smoothing section 11 smoothes the scaled image information. In this embodiment, the correction coefficient for the smoothing process is set as shown in FIG. That is, the scaling factor is 15
When it is less than 0%, the correction coefficients b and h are set to "1.5", the correction coefficients d and f are set to "1.25", and the correction coefficient e is set to "2.5". On the other hand, when the scaling factor is 150% or more,
The correction coefficients b and h are set to "1.25", the correction coefficients d and f are set to "1", and the correction coefficient e is set to "3.5".

The halftone binarization unit 12 smoothes the image information with such a correction coefficient. Then, after the smoothed image information is binarized, the obtained image is recorded or transmitted.

As described above, in this embodiment, the correction coefficients d and f in the main scanning direction are set to values smaller than the correction coefficients b and h in the sub-scanning direction, and the scaling factor is the same as in the above-described embodiments. When is larger, those correction coefficients are set to a smaller value as a whole.

As a result, the density change can be suppressed appropriately in each of the main scanning direction and the sub-scanning direction, and even if the scaling ratio changes, the degree of suppression of the density change can be maintained. A good image is always obtained.

Next, an image processing apparatus according to the eleventh embodiment of the present invention will be described.

FIG. 27 shows the image processing apparatus of this embodiment, and the same reference numerals as those in FIG. 15 or 19 denote the same parts.

In the present embodiment, the operator arbitrarily specifies whether or not to execute the scaling process when starting the apparatus. This designation information is input to the scanner unit 10, the main scanning direction scaling unit 7, and the smoothing unit 11. It is assumed that the scaling factor for executing the scaling process is fixedly set in advance.

When the scaling process is not executed, the scanner section 10 scans the original image by sub-scanning at a predetermined standard pitch. When execution of the scaling process is designated, the original image is read by sub-scanning at a preset constant pitch.

The main scanning direction scaling unit 7 inputs the image information read by the scanner unit 10 to the smoothing unit 11 as it is, when the scaling process is not executed. When executing the scaling process, the image information is scaled in the main scanning direction at the set scaling ratio and input to the smoothing unit 11.

The smoothing section 11 smoothes the input image information. In this embodiment, the correction coefficient in this case is set as shown in FIG. That is, when the scaling processing is not executed, the correction coefficients b, d, f, and h are set to “1.5” and the correction coefficient e is set.
Are set to “2” respectively. On the other hand, when executing the scaling process, the correction coefficients b and h are set to “1.25”, the correction coefficient d and
f is set to "1.5" and the correction coefficient e is set to "2.5".

The smoothing section 11 smoothes the image information with such a correction coefficient. Then, similarly to each of the above-described embodiments, the smoothed image information is binarized, and the obtained image is recorded or transmitted.

As described above, in the present embodiment, when the scaling processing is executed, the correction coefficients b and h in the sub-scanning direction are set to values smaller than the correction coefficients d and f in the main scanning direction. .

Since the scanner unit 10 changes the sub-scanning pitch to change the image information in the sub-scanning direction, the obtained image information is compared with the image information which is changed by the above-described various changing processing methods, The concentration change during the period is always gentle.

In this embodiment, when executing the scaling process,
Since the correction coefficients b and h in the sub-scanning direction are reduced to reduce the degree of suppression of the density change, the density is appropriately suppressed in each of the main scanning direction and the sub-scanning direction, and a good image is always obtained. Will be available.

Next explained is an image processing apparatus according to the twelfth embodiment of the invention.

The image processing apparatus of this embodiment has the same configuration as that of FIG. And when starting the device,
The operator specifies a desired scaling factor. As shown in FIG. 29, this designation information is input to the scanner unit 10, the main scanning direction scaling unit 7 and the smoothing unit 11.

When the apparatus is activated, the scanner section 10 reads a document image under specified conditions and outputs image information. The main scanning direction scaling unit 7 scales the image information in the main scanning direction at a designated scaling ratio. Then, the smoothing unit 11 smoothes the scaled image information.

In this embodiment, the correction coefficient in this case is shown in FIG.
Set as shown in 0. That is, the scaling factor is 150%
If it is less than, the correction coefficients b and h are set to "1.25", the correction coefficients d and f are set to "1.5", and the correction coefficient e is set to "2.5". On the other hand, when the scaling factor is 150% or more, the correction coefficients b and h are “1”, the correction coefficients d and f are “1.25”,
The correction coefficient e is set to "3.5", respectively.

The smoothing section 11 smoothes the image information with such a correction coefficient. Then, the smoothed image information is binarized, and the obtained image is recorded or transmitted.

As described above, in the present embodiment, when the image information is scaled, the degree of suppression of the density change in the sub-scanning direction is made lower than that in the main scanning direction as in the case of the above-described embodiment, while the scaling factor is changed. When it becomes larger, the degree of suppression is further lowered as a whole.

As a result, the density change can be suppressed appropriately regardless of the scaling factor, and a good image can always be obtained.

In each of the above embodiments, the operator arbitrarily specifies the necessity of the scaling process, the scaling method, the scaling factor, etc., but the apparatus automatically sets them according to the operating conditions. You may do it. For example, like a known facsimile communication procedure, it is possible to automatically set according to the device function of the other party.

Further, the correction coefficient for MTF correction or smoothing processing is changed in two steps for one condition, but it may be changed in three or more steps.

Further, the scaling of the image information is carried out by the linear interpolation method and the nearest neighbor method, and the method of changing the sub-scanning pitch at the time of reading the image. Can be similarly applied. In that case, the degree of correction for MTF correction or smoothing processing may be similarly changed according to the property of the obtained image information.

[0151]

As described above, according to one invention of the present application, when the density change between adjacent pixels of the scaled image information is steep, the correction degree of the MTF correction is set to be low and the density change is reduced. In the case of a gradual change, the correction degree is set to be high, so that it is possible to obtain a good image by always appropriately enhancing the density change of the image information.

In another invention, when the density change between adjacent pixels of the scaled image information is sharp, the correction degree of the smoothing process is set low, while when the density change is gentle, Since the correction degree is set to be high, it is possible to always suppress the change in the density of the image information appropriately and obtain a good image.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing pixel positions before and after scaling in a two-dimensional scaling process.

FIG. 3 is a flowchart of an image density setting operation by a two-dimensional nearest neighbor method.

FIG. 4 is an explanatory diagram of an image region of interest in MTF correction and smoothing processing.

FIG. 5 is an explanatory diagram of correction coefficients for MTF correction and smoothing processing.

FIG. 6 is an explanatory diagram showing a method of setting the correction coefficient.

FIG. 7 is a block configuration diagram of a portion different from FIG. 1 in the image processing apparatus of the second embodiment.

FIG. 8 is an explanatory diagram showing a method of setting a correction coefficient for MTF correction in the above embodiment.

FIG. 9 is a block configuration diagram of an image processing apparatus of a third embodiment.

FIG. 10 is an explanatory diagram showing pixel positions before and after scaling in a one-dimensional scaling process.

FIG. 11 is a flowchart of an image density setting operation by the one-dimensional nearest neighbor method.

FIG. 12 is an explanatory diagram showing a method of setting a correction coefficient for MTF correction in the above embodiment.

FIG. 13 is a block configuration diagram of a portion different from FIG. 9 in the image processing apparatus of the fourth embodiment.

FIG. 14 is an explanatory diagram showing a method of setting a correction coefficient for MTF correction in the above embodiment.

FIG. 15 is a block configuration diagram of an image processing apparatus of a fifth embodiment.

FIG. 16 is an explanatory diagram showing a method of setting a correction coefficient for MTF correction in the above embodiment.

FIG. 17 shows an image processing apparatus according to a sixth embodiment of FIG.
FIG. 6 is a block configuration diagram of a portion different from FIG.

FIG. 18 is an explanatory diagram showing a method of setting a correction coefficient for MTF correction in the above embodiment.

FIG. 19 is a block configuration diagram of an image processing apparatus according to a seventh embodiment of the present invention.

FIG. 20 is an explanatory diagram showing a method of setting a correction coefficient for smoothing processing in the above-described embodiment.

FIG. 21 shows the image processing apparatus of the eighth embodiment shown in FIG.
FIG. 6 is a block configuration diagram of a portion different from FIG.

FIG. 22 is an explanatory diagram showing a method of setting a correction coefficient for smoothing processing in the above embodiment.

FIG. 23 is a block configuration diagram of an image processing apparatus of a ninth embodiment.

FIG. 24 is an explanatory diagram showing a method of setting a correction coefficient for smoothing processing in the above embodiment.

FIG. 25 shows the image processing apparatus of the tenth embodiment shown in FIG.
3 is a block configuration diagram of a part different from FIG.

FIG. 26 is an explanatory diagram showing a method of setting a correction coefficient for smoothing processing in the above embodiment.

FIG. 27 is a block configuration diagram of an image processing apparatus of an eleventh embodiment.

FIG. 28 is an explanatory diagram showing a method of setting a correction coefficient for smoothing processing in the above embodiment.

FIG. 29 shows an image processing apparatus according to the twelfth embodiment shown in FIG.
7 is a block configuration diagram of a portion different from 7.

FIG. 30 is an explanatory diagram showing a method of setting a correction coefficient for smoothing processing in the above embodiment.

[Explanation of symbols]

 1, 10 Scanner Section 2 Magnification Section 3 MTF Correction Section 4 Binarization Section 5 Plotter Section 6 Transmitting Section 7 Main Scanning Direction Magnification Section 8 Sub-scanning Direction Magnification Section 9 Switch 11 Smoothing Section 12 Halftone Binarization Section

Claims (12)

[Claims] 1. A method of processing image information, comprising: performing MTF correction for emphasizing shading after performing a scaling process for increasing or decreasing the number of pixels on multi-gradation image information representing shading of an image.
When the density change between adjacent pixels of the scaled image information is sharp, the correction degree of the MTF correction is set low, while when the density change is gentle, the correction degree is set high. Image information processing method. 2. The difference in the gradual change in the density change is caused by the difference in the scaling processing method, and the correction degree is set according to the scaling processing method adopted.
How to process the described image information. 3. The correction degree is set low when the nearest neighbor method is adopted as the scaling processing method, while the correction degree is set high when the linear interpolation method is adopted. The method of processing image information described in 2. 4. The image information according to claim 2, wherein when the scaling processing method is different between the main scanning direction and the sub-scanning direction of the image information, the correction degree is set for each direction. Processing method. 5. The difference in gradual change of the density change is caused by the magnitude of the scaling factor, and the correction degree is set high according to the magnitude of the scaling factor. Image information processing method. 6. When the scaling processing of the image information in the sub-scanning direction is executed by changing the sub-scanning pitch when reading an original, and the scaling processing of the main scanning direction is executed by increasing or decreasing the number of pixels. 2. The image information processing method according to claim 1, wherein the correction degree in the sub-scanning direction is set high and the correction degree in the main scanning direction is set low. 7. A method of processing image information, comprising: performing a scaling process for increasing or decreasing the number of pixels on multi-gradation image information representing a shade of an image, and then performing a smoothing process for gently correcting the shade. When the density change between adjacent pixels of the scaled image information is sharp, the correction degree of the smoothing process is set high, while when the density change is gentle, the correction degree is set low. How to process image information. 8. The difference in gradual change of the density change is caused by the difference in the scaling processing method, and the correction degree is set for each scaling processing method adopted.
How to process the described image information. 9. The correction degree is set high when a nearest neighbor method is adopted as the scaling processing method, while the correction degree is set low when a linear interpolation method is adopted. 8. A method of processing image information described in 8. 10. The image information according to claim 8, wherein when the scaling processing method is different in the main scanning direction and the sub scanning direction of the image information, the correction degree is set for each direction. Processing method. 11. The gradual difference in the density change is caused by the magnitude of the scaling factor, and the correction degree is set low according to the magnitude of the scaling factor. Image information processing method. 12. When the scaling processing of the image information in the sub-scanning direction is executed by changing the sub-scanning pitch when reading the original, and the scaling processing of the main scanning direction is executed by increasing or decreasing the number of pixels. 8. The image information processing method according to claim 7, wherein the correction degree in the sub-scanning direction is set low and the correction degree in the main-scanning direction is set high.