JPH083844B2 - Image processing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus that detects the density of input image information to perform image processing.

[Prior Art] As a conventional device of this type, there is, for example, a copying machine, in which an original image is digitally read by a solid-state image sensor such as a linear image scanner (CCD), and the read image is enlarged or reduced. Some have a scaling function. As a general variable magnification method in these devices, the magnification in the feeding direction is changed by changing the scanning speed in the sub-scanning direction (moving direction of sending CCD). Further, the magnification in the main scanning direction is changed by storing or thinning out pixels in the main scanning direction (direction orthogonal to the feeding direction).

For example, when performing three times the enlargement processing, the sub-scanning direction movement speed of the time constant times the V _1, a moving speed in the sub-scanning direction and V _1/3, also, the main scanning direction, 1 pixel The image data of 3 times enlargement processing is formed by repeatedly outputting the image data of 3 times.

[Problems to be Solved by the Invention] However, when the scaling processing is performed only by such a method, as shown in FIG. 6, since the enlarged output image has the same data in units of 3 pixels, It is preferable for a character or symbol having a single density, but it is not preferable for a variable-magnification process for a smooth halftone image such as a photograph in terms of image smoothness.

Therefore, it is possible to determine whether the image data that has undergone the scaling process is subjected to the first derivative of the density change to perform the density difference smoothing process. However, when the density difference of the read image is detected by taking the first derivative of the image data after the scaling process, the scaling process is performed by thinning out the reduction process or interpolating the enlargement process. It is troublesome that the differential regions of the differential are provided corresponding to the scaling factors and the primary differential is calculated for each of them.

The present invention has been made in view of the above-mentioned prior art, in which the image tone of an input image is determined based on an image before scaling, and the determination is efficiently and accurately performed. By correcting the image based on the spatial frequency filter according to the determination result, the correction can be performed only by the processing based on the filter and faithfully to the original image, and
It is an object of the present invention to provide an image processing device that can generate a favorable scaled image.

[Means for Solving Problems] In order to achieve the above object, the image processing apparatus of the present invention has the following configuration. That is, the input image information is scaled, the scaled image information is calculated by a spatial frequency filter having a predetermined characteristic, and an image processing apparatus that forms an output image inputs the image information. Inputting means, a judging means for judging the image tone of the image represented by the image information based on the image information input by the inputting means, and a multi-step scaling factor for the scaling process performed on the input image. Setting means for setting the image information input by the input means, a scaling means for performing a scaling process according to the scaling ratio set by the setting means, and based on the determination result by the determination means. Filter setting means for setting the characteristics of the spatial frequency filter, and correction calculation of the pixel value of the image information after the scaling by the scaling means according to the spatial frequency filter having the set characteristics. And a correction means for performing.

[Operation] In the configuration of the present invention, the input image is scaled according to the set scaling ratio. On the other hand, the characteristic of the spatial frequency filter is set based on the image tone of the input image judged by the judging means. Then, the pixel value of the image information after scaling is corrected according to the set spatial frequency filter.

Embodiments Embodiments according to the present invention will be described in detail below with reference to the accompanying drawings.

Further, in the present embodiment, a case will be described in which it is applied to the scaling processing of the input image by detecting the first-order differential which is the density change of the input image.

As an image reading method, for example, a large number (for example, 128) of picture elements in a solid-state image sensor such as a linear image scanner (CCD) are arranged in the sub-scanning direction, and image data in the image sensor is sub-scanned. It may be possible to read digitally by sending in the scanning direction. When the CCD width is 8 mm, for example, an image is read with a width of 8 mm for each scan. That is, in Fig. 7, 8 mm from (a) to (b)
After reading the image with the width and then returning from (b) to (c), the image data is read in the same manner from (c) to (d).

Further, as an image forming mechanism, for example, a multi-bubble jet head (head portion) having 128 nozzles in a width of 8 mm
As shown in FIG. 8, images are formed while scanning with a width of 8 mm from (e) to (f). Then, return from (f) to (g). After that, similarly, an image will be formed by 8 mm.

The image processing apparatus according to the present embodiment will be described with reference to FIG. 4 based on the above-described image input and output mechanism.

In the figure, 31 is an image reading unit that reads a document and digitizes and outputs the density level of image information. 32 is a pixel data output from the image reading unit 31 and reads the pixel data at any time to change the density of the pixel of interest. It is a first-order differentiator that calculates Reference numeral 33 is a scaling unit that performs scaling processing on the image information input by the scaling instruction from the control unit 34, and 35 is a smoothing unit that smoothes the image data that has been scaled by the scaling unit 33. It is a department. A selector 36 switches the image data output from the smoothing unit 35 and the scaling unit 33 and outputs the image data to the image processing unit 37. A printer unit 38 visualizes and records the image data processed by the image processing unit.

The image signal read by the image reading unit 31 and converted into digital density data passes through the primary differentiating unit 32, and from the pixel data before and after the pixel data of interest, the rate of change in density near the pixel of interest (first differential value D). Is calculated from the following formula.

D = {| (a + b)-(d + e) |)} / 2 Equation 1 where D: primary differential value of the target pixel, a: pixel data two pixels after the target pixel, b: one pixel after the target pixel Pixel data, d: pixel data one pixel before the target pixel, and e: pixel data two pixels before the target pixel.

Further, when the first-order differential value D is a predetermined value or more, it is "1", and when it is less than that value, it is "0".
(Hereinafter, this signal is referred to as a density change signal) is output to the conversion unit 33 described later.

Equation 1 calculates the density change of the pixels on both sides including the pixel of interest, and the greater the change, the larger D becomes. Therefore, when the primary differential value D is equal to or larger than the predetermined value, it is determined that the input image has a character or a symbol that is single density information,
If it is less than the predetermined value, it is determined that the information is halftone image information such as a photograph.

The pixel data read by the image reading unit 31 and the density change signal from the primary differentiating unit 32 are both input to the scaling unit 33.

Further, the pixel data input to the scaling unit 33 is controlled by the control unit 34 according to the designated magnification by an operation switch (not shown) or the like.
The magnification is changed in accordance with the instruction from, and is temporarily stored in the magnification RAM 33a in the magnification unit 33.

Next, the image data read from the scaling RAM 33a is input to the smoothing unit 35, and the density change signal is input to the control unit 34. In the control unit 34, the control unit 34 outputs a selector signal to the selectors 35 and 36 under the conditions shown in Table 1.

Image data smoothed by the smoothing unit 35 and image data from the scaling unit 33 are input to the selector 36, and the control unit 34 selects one of them. It will be.

In this way, depending on the select signal, the scaling unit 33 or the smoothing unit
The output image is selected from 35, and the selected image data is output from the selector 36.

The image data selected by the selector 36 is processed by the image processing unit 37, converted into dot data, and then output to the printer unit 38 to form an output image in the printer unit.

Next, the operation of the temporary differentiator 32 will be described with reference to FIG. In this primary differentiator 32, the previously extended formula 1 is obtained.

Now, the pixel data converted into the density data output from the image reading unit 31 is processed by the latch unit 41 as the video lock φ.
Is delayed by one pixel and then input to the adder 42. In the adder 42, the pixel data and the pixel data delayed by one pixel are input and added. The output from the adder 42 is input to the latch unit 43 and the inverter 45. The latch unit 43 and the latch unit 44 are delayed by one pixel by the video clock φ and are input to the adder 46 later. Also the inverter
The data input to 45 is inverted and becomes a one's complement and output to the adder 46. In the adder 46, "1" is added to the input data from the inverter 45, the 1's complement is made into the 2's complement, and the result is added to the output of the latch 44 to output the output image data of the adder 42 and the output data of the latch 44. Is being subtracted from. Next, the output of the adder 46 is input to the table ROM 47 as an address. The table ROM 47 is pre-stored so that the output data becomes 1/2 of the input address. In this way, it is halved by the table ROM 47 and is output as the primary differential data. Furthermore, the primary differential data input to the comparator 48 is compared with a predetermined set value, and if the primary differential value is larger than the set value, it is set to "1", and if it is smaller, it is set to "0", and the result is the density change. It is output as a signal. The set value set in the comparator 48 can be arbitrarily set according to an instruction from the outside.

Next, the processing performed by the scaling unit 33 will be described with reference to FIG.

Here, in the scaling processing in the sub-scanning direction, the sub-scanning speed V1 of the printer of the reading unit is made constant and the speed of the reader is set to V ₁ / n.
The description will be omitted as it is performed by changing to (n: scaling factor).

For the scaling processing in the main scanning direction, a scaling mode signal is input to the memory control unit from a control circuit (not shown). The memory control unit includes an address clock generator 12 and a write pulse generator 13, and a variable-magnification buffer memory 11-
Address counter 14-a, 14 when writing to a, 11-b
The number of clock pulses of -b is determined, and the write pulse of the variable power buffer memory is generated. This is achieved by increasing or decreasing the number of clock pulses and the write pulse according to the scaling factor. This variable buffer memory is
Writing and reading are performed with variable-size buffer memories 11-a and 11-
Alternate in b. For example, at the time of n-fold enlargement, the same pixel data is written to n addresses in 11-b of the variable-magnification buffer memories 11-a and 11-b which are in the write mode (w). In addition, at the time of 1 / n reduction, one pixel out of n pixels is written at one address, and when the read mode is entered, if the address is stepped up by the video clock φ, pixel data is interpolated. , Thinning will be achieved.

Further, although the motor speed on the image reading side is changed in this embodiment, the motor speed on the recording side may be changed.

Next, the processing operation of the smoothing unit 35 will be described with reference to FIG.

The smoothing unit 35 has a matrix corresponding to the scaling factor, for example, 1 × 2 for 2 × magnification and 1 × 3 for 3 × magnification.
Has a first order matrix. In this matrix, the following formula is calculated.

That is, in the case of 2 times enlargement, D = 1/2 (a + b): 1 × 2 In the case of 3 times enlargement, D = 1/3 (a + b + c): 1 × 3 where D is the image output data of the pixel of interest and b Is the image input data of the target pixel, a is the image input data one pixel after the target pixel data, and c is the image input data one pixel before the target pixel data.

The size of this matrix is switched according to the enlargement ratio. In the present embodiment, only 1 × 2 and 1 × 3 matrices are used, but 1 × n (n
There is no problem even if a matrix size of (double magnification) is used.

Now, the smoothing unit 35 performs the smoothing process as follows.

[In the case of equal magnification] The output image data of the variable magnification buffer is delayed by one pixel by the latch 29 and goes to the selector 27. The selector 27 selects and outputs the same size image data according to the selection signal from the control unit 23.

[Double Enlargement] The latched image 21 of the enlarged image data is delayed by one pixel. The delayed image data is added to the input enlarged image data by the adder 24. The added data is output to the table ROM 28 as an address, and the averaged data is output to the selector 27. The table ROM 28 has a structure in which the input and output correspond to 1: 1. The selector 27 selects and outputs the output data of the table ROM 28 according to the selection signal from the control unit 23 as described above.

[In the case of 3 times expansion] The data delayed by the latch 21 is delayed by another pixel by the latch 22. The output of the latch 22 and the output of the adder 24 are added by the adder 25, and the result is entered in the table ROM 26. After averaging to 1/3 in the table ROM 26, it enters the selector 27. The selector 27 receives the table ROM 26 according to the selection signal from the control unit 23.
Select the output of and output.

In this way, processing is performed corresponding to each magnification.

FIG. 5 shows an output image when the smoothing unit 35 smoothes the image data which has been magnified 3 times by the magnification changing unit 33, for example, as in the conventional enlarging process (FIG. 6). As is clear from the output image in which three target image data are output side by side (in the case of 3 times enlargement), it is possible to process the output image after the enlargement processing by smoothing the density steps.

The smoothing process as described above is performed when the density change signal from the primary differentiating unit 32 is “0”, that is, the primary differential value D in the equation 1 becomes a predetermined value or less and the input image is a halftone image. When the determination is made, the control unit 34 outputs a select signal to that effect to the selector 36, thereby outputting the image data from the smoothing unit 35 to the image processing unit 37.

When the primary differential value D is equal to or larger than the predetermined value, the density change signal to the control unit 34 becomes "1", and the control unit 34 outputs a sect signal to that effect to the selector 36 so that the magnification changing unit 33 That is, the image data of is output to the image processing unit 37.

As described above, according to the present embodiment, by calculating the temporary differential value (density change rate) of the density of the input image before the scaling processing, the calculation is performed without changing the pixel area related to the calculation. It becomes possible. Further, it is possible to judge from the first-order differential value whether the input image is single image information such as a character symbol or halftone image information such as a photograph with a very simple configuration.

Further, in this embodiment, the density change of the input image is calculated,
The case where it is applied to the scaling processing has been described, but the present invention is not limited to this, and the present invention can be applied to other image processing apparatuses having a function of detecting an edge portion of an input image, for example.

Further, in the present embodiment, the primary differential value is calculated from the pixel data of two pixels before and after the pixel of interest in order to calculate the primary differential value. However, the number of read pixels can be two adjacent pixels of the pixel of interest. It doesn't matter, more than that.

Furthermore, when the present embodiment is applied to the scaling processing, the scaling processing when it is detected that there is halftone image information in the input image when the input image information is scaled and output, The discontinuity of the density change of only the halftone image information can be made smooth by the small-scale circuit configuration.

Further, in the present embodiment, the description has been given only to the case where the variable magnification is 1 ×, 2 ×, and 3 ×, but it goes without saying that other magnifications can be applied.

Further, it is obvious that the image reading device and the output device for forming the output image are not limited, and for example, the output device may be a laser beam printer or the like.

[Effects of the Invention] As described above, according to the present invention, the image tone of an input image is determined based on the image before scaling, so that the determination can be performed efficiently and accurately, and the scaling factor Since the scaled image is corrected based on the spatial frequency filter according to the determination result, the correction only needs to be performed based on the filter, so that a good scaled image can be generated faithfully to the original image.

[Brief description of drawings]

FIG. 1 is a block diagram of the primary differentiation unit, FIG. 2 is a block diagram of the variable power unit, FIG. 3 is a block diagram of the smoothing unit, FIG. 4 is an overall block diagram of the image processing apparatus of this embodiment, and FIG. FIG. 5 is a diagram showing an example of the enlarging process of this embodiment, FIG. 6 is a diagram showing a conventional enlarging process, FIG. 7 is a diagram showing the operation of the image reading process, and FIG. 8 is forming an output image. It is a figure which shows the processing operation at this time. In the figure, 11-a, 11-b ... Magnification buffer RAM, 12 ... Address clock generator, 13 ... Write pulse generator, 14-
a, 14-b ... Counter, 21,22,29 ... Latch, 24,25 ...
... Adder, 26, 28 ... Table ROM, 23 ... Smoothing control section, 27 ... Selector, 31 ... Image reading section, 32 ... First derivative section, 33 ... Variable magnification section, 34 ... Control Section, 35 ... smoothing section, 36 ... selector, 37 ... image processing section, 38 ... printer section, 41, 43, 44 ... latch, 42, 46 ... adder, 45 ...
Inverter, 47 ... table ROM, 48 ... comparator.

Claims (1)

[Claims] Claim: What is claimed is: 1. An image processing apparatus for performing a scaling process on input image information, performing an operation on a scaled image information by a spatial frequency filter having a predetermined characteristic, and forming an output image. Input means for inputting information, judging means for judging the image tone of the image represented by the image information based on the image information input by the input means, and a scaling factor for the scaling process performed on the input image. Setting means for setting in multiple stages, a scaling means for performing a scaling process on the image information input by the input means in accordance with the scaling ratio set by the setting means, and a determination made by the determination means. Filter setting means for setting the characteristic of the spatial frequency filter based on the result, and correction performance of the pixel value of the image information after the scaling by the scaling means according to the spatial frequency filter of the set characteristic. The image processing apparatus characterized by comprising a correction means for performing.