JP3526936B2 - Image magnifier - 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 enlarging device for digital images.

[0002]

2. Description of the Related Art Conventionally, in image enlargement, a method using linear interpolation has been known as a method that can be realized by relatively simple calculation, and an image that does not cause large jaggies as in the zero-order hold method can be obtained. , A device using this method becomes relatively simple. However, there is a drawback that an image is blurred, and as an image enlarging apparatus which suppresses the blur, for example, it is described in "Method and apparatus for enlarging / reducing digital image" disclosed in Japanese Patent Application Laid-Open No. 4-330858. There is an image magnifying device.

FIG. 6 shows the configuration of the conventional image enlarging device. Reference numeral 601 denotes a high-frequency emphasis filter design unit, 60
2 is a part for obtaining a cubic spline function, 603 is a filtering and convolution part using an interpolation filter, 604
Is a magnified image generator.

Next, the operation of the conventional image enlarging device will be described. First, with respect to the original image, the high-frequency emphasis filter designing unit 601 standardizes the coefficient (impulse response) of the digital filter so that the DC gain becomes 1 so that the color tone of the original image does not change. Then, a cubic spline function for interpolating the impulse response of the filter obtained as a result is obtained in a portion 602 for obtaining a cubic spline function, and the obtained cubic spline function is used to calculate an interpolation filter. The filtering and convolution unit 604 designs an enlargement interpolation filter, and the enlarged image generation unit 605 filters the image signal to generate an actual enlarged image.

[0005]

However, in the conventional image enlarging apparatus as described above, although the blur due to the enlarging is eliminated, the calculation is complicated because the cubic spline interpolation is used, and the apparatus becomes complicated. Had the problem.

In order to solve the above problems, the present invention provides
An object of the present invention is to provide an image enlarging device that can obtain an enlarged image using simple calculation, with less blurring of the image, and without causing large jaggies.

[0007]

In order to achieve the above object, the present invention provides an intermediate value detecting section for outputting two values obtained by removing the maximum value and the minimum value from four input values, and the intermediate value detecting section. An output value of the detection unit is used as an input value, and an average calculation unit that outputs an average value of the input values is provided.

[0008]

According to the present invention, the brightness value of four pixels forming a square area is input, the intermediate value detecting section outputs two brightness values excluding the maximum value and the minimum value, and the average calculating section has the above-described structure. By outputting the average value of the two brightness values and using the output value as the brightness value of the pixel in the center of the square area, it is possible to obtain a magnified image with less blur and large jaggies by simple calculation. .

[0009]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. First, an image enlarging apparatus according to the first embodiment of the present invention will be described with reference to FIG. In FIG.
An input memory 101 stores an original digital image (hereinafter referred to as an original image) and outputs a luminance value of a designated first read address. A reference numeral 102 indicates a maximum value and a minimum value from four input values. An intermediate value detecting unit that outputs the two excluded values, 103 is an average calculating unit that uses the output value of the intermediate value detecting unit 102 as an input value, and outputs an average value of the input values, and 104 is an output value of the input memory 101 or an average value. It is an output memory that stores the output value of the calculation unit 103 in a specified write address and outputs the value of the specified address to the intermediate value detection unit 102 when the second read address is specified.
Reference numeral 105 denotes a control unit, which first sequentially designates a first read address that stores the brightness value of each pixel of the image stored in the input memory 101, and simultaneously outputs the output memory 104.
In addition, a write address for storing the brightness value of each pixel located after the enlargement is sequentially specified, and then the brightness values of four pixels in the vicinity of the pixel whose brightness value of the enlarged image is undetermined are stored. The address of the output memory 104 is designated as the second read address in the output memory 104, and the write address for storing the luminance value of the pixel whose luminance value is undecided is designated in the output memory 104. The operation of controlling the output value of 103 to be stored in the output memory 104 is repeated until the luminance values of all pixels of the enlarged image are obtained.

Next, the operation of the above embodiment will be described. Prior to enlarging the image, the brightness value of each pixel of the original image is stored in the input memory 101. First, the control unit 10
5 sequentially designates, as a first read address, an address in which the luminance value of each pixel of the original image is stored in the input memory 101, and at the same time, the output memory 104 stores pixels of pixels located after the original image is enlarged. Addresses for storing brightness values are sequentially designated as write addresses. As a result, the brightness value of each pixel of the original image stored in the input memory 101 is stored in the output memory 104 as the brightness value of the corresponding pixel after enlargement.

Next, among the pixels of the enlarged image, the four addresses for storing the brightness values of the pixels located at the four corners of the square area and for which the brightness values have already been determined are used as the second read addresses in the output memory. Of the four luminance values designated by 104, the maximum value and the minimum value are removed by the intermediate value detecting unit 102, and the remaining two luminance values are
It is output to the average calculation unit 103. The average value of the two brightness values output from the intermediate value detection unit 102 is calculated by the average calculation unit 103 and output to the output memory 305. Here, the control unit 105 uses the address for storing the brightness value of the pixel at the center of the square area as the write address in the output memory 1
04, and the output memory 104 stores the average value output by the average calculation unit 103 at that address. Control unit 1
In 05, an enlarged image is generated by repeating the above operation until the luminance values of all the pixels of the enlarged image are obtained.

FIG. 2 is a schematic diagram showing how an enlarged image is generated. The pixels g1, g2, g3, g4, g5, g in FIG. 2A are arranged at the enlarged positions of the pixels of the original image.
It is 6. First, the brightness value of g7 is obtained from the brightness values of the pixels g1, g2, g3, and g4 by the above process, and the pixel g2
The brightness values of g5, g6 and g3 are obtained by the above processing,
The luminance value of the pixel g8 is calculated. Next, as shown in FIG. 2B, from the luminance values of the pixels g2, g8, g3, and g7, the pixel g
The luminance value of 9 is obtained by the above process. Similarly, the luminance values of the pixels g10, g11, g12, g13, g14, g15 are obtained. Hereinafter, as shown in FIG. 2C, the brightness value of the pixel located at the center of the square area is obtained from the brightness values of the four pixels forming the smaller square area, and the brightness values of all the pixels in the enlarged image are obtained. The same process is repeated until is obtained.

FIG. 3 is an example of an enlarged image obtained by this embodiment, and is an example in which an image consisting of white and black is enlarged twice. In this method, the pixels g20, g21, g22,
Only g23 becomes gray and the edges are hard to blur. If linear interpolation is used, the luminance value of the pixel gg is also gray and the edges are blurred.

As described above, according to this embodiment, the circumference 4
Of the pixel brightness, the average value of the two brightness values excluding the maximum and minimum brightness values is set as the brightness of the center pixel, so that there is little blurring with simple calculation, and enlargement without large jaggies occurs. Images can be obtained.

When the brightness value is represented by a set of color component values, for example, (R, G, B), the intermediate value detecting unit 1
As the value to be compared in order to obtain the maximum value and the minimum value in 02, the values of the color components are added or weighted and compared.

(Embodiment 2) Next, an image enlarging apparatus according to a second embodiment of the present invention will be described with reference to FIG. In FIG. 4, reference numeral 401 denotes an input memory that stores an original digital image (hereinafter referred to as an original image), and that outputs a luminance value of a designated first read address.
Is a hue calculation unit that obtains a hue for each of the four input luminance values and outputs four pieces of data that are combined with the respective input luminance values. Reference numeral 403 is an input of the output data of the hue calculation unit 403. An intermediate hue detection unit that selects two input data having a hue close to the average hue and outputs only the brightness value of the selected input data, and 404 uses the output value of the intermediate hue detection unit 403 as an input value, and averages the input values. An average calculation unit 405 which outputs a value stores the output value of the input memory 401 or the output value of the average calculation unit 404 at a designated write address, and when a second read address is designated, the designated value is designated. The value of the address is calculated by the hue calculator 402.
An output memory 406 for outputting to the output memory 406 is a control unit. First, the first read address storing the brightness value of each pixel of the image stored in the input memory 401 is sequentially designated, and at the same time, the output memory 405 stores the above An output memory in which each pixel sequentially specifies a write address for storing the brightness value of the pixel located after the expansion, and then stores the brightness values of four pixels near the pixel whose brightness value of the enlarged image is undetermined The output value of the average calculation unit 404 is specified by designating the address of 405 as the second read address in the output memory 405, and designating the write address for storing the value of the pixel whose value is undetermined in the output memory 405. Is stored in the output memory 405 until the luminance values of all pixels of the enlarged image are obtained.

Next, the operation of the above embodiment will be described. Prior to the enlargement of the image, the brightness value of each pixel of the original image is stored in the input memory 401. First, the control unit 406 sequentially designates, as the first read address, the address in which the luminance value of each pixel of the original image is stored in the input memory 401, and at the same time, after the original image is enlarged in the output memory 405. Addresses for storing the brightness values of the pixels located are sequentially designated as write addresses. As a result, the brightness value of each pixel of the original image stored in the input memory 401 is stored in the output memory 405 as the brightness value of the corresponding pixel after enlargement.

Next, among the pixels of the enlarged image, the four addresses for storing the brightness values of the pixels located at the four corners of the square area and for which the brightness values have already been obtained are used as the second read addresses as the output memory. The four luminance values designated by the reference numeral 405 are read out and input to the hue calculation unit 402, and the hue is calculated and four data combined with the input luminance value are output to the intermediate hue detection unit 403. . Here, for example, when one luminance value is input to the hue calculation unit 402 as a set of color component values (R, G, B), one output data of the hue calculation unit 402 is (hue, R, G , B).

Next, the intermediate hue detecting unit 403 outputs four data (hue, R, G, B) output from the hue calculating unit 402.
Out of the two selected data (hue, R, G, B) having a hue close to the average hue of the four hues, the brightness value (R , G,
Only B) is output to the average calculation unit 404. Average calculator 4
04 calculates the average of the two luminance values output from the intermediate hue detection unit 403 and outputs the average to the output memory 405. Here, the control unit 406 specifies the address for storing the brightness value of the pixel at the center of the square area as the write address in the output memory 405, and the output memory 405 stores the address at that address.
The average value output by the average calculator 404 is stored. The control unit 406 repeats the above operation until the luminance values of all the pixels of the enlarged image are obtained, thereby generating the enlarged image.

As described above, according to this embodiment, the circumference 4
By using the average value of two brightness values whose hue is close to the average value among the brightness values of the pixel as the brightness value of the central pixel, it is possible to obtain a magnified image with less blurring and large jaggies by simple calculation. it can.

(Embodiment 3) Next, an image enlarging apparatus according to a third embodiment of the present invention will be described with reference to FIG. In FIG. 5, reference numeral 501 denotes an input memory that stores the original digital image and outputs the luminance value of the designated first read address, and 502 indicates the maximum value and the minimum value from the four input luminance values. If the difference between the maximum values and the minimum value is greater than a predetermined threshold value, the two input luminance values excluding the maximum value and the minimum value are output as the first output value, and if the difference between the maximum value and the minimum value is less than the threshold value. Sets four input luminance values to the second
The intermediate value detection unit 503 outputs the second output value of the intermediate value detection unit 502 as an input, and the hue is calculated for each of the four input luminance values and four pieces of data including the input luminance value are obtained. A hue calculation unit 504 for output receives the output data of the hue calculation unit 503 as input, selects two input data having a hue close to the average hue of the hues of the four input data, and outputs only the brightness value of the selected input data. An intermediate hue detecting unit 505 for outputting, an average calculating unit 506 for outputting an average value of the input values by using the first output value of the intermediate value detecting unit 502 or an output value of the intermediate hue detecting unit 504 as an input value, and 506 an input memory. Or the output value of the average calculation unit 505 is stored in the designated write address, and the second read address is designated, the value of the designated address is stored in the intermediate value detection unit 502. An output memory 507 for outputting is a control unit, which first sequentially designates a first read address storing the brightness value of each pixel of the image stored in the input memory 501, and at the same time, outputs the above-mentioned information to the output memory 506. An output memory 506 in which each pixel sequentially designates a write address for storing the brightness value of a pixel located after enlargement, and then stores the brightness values of four pixels in the vicinity of the pixel whose brightness value of the enlarged image is undetermined. Is designated as the second read address in the output memory 506, and the write address for storing the brightness value of the pixel whose brightness value is undetermined is output memory 50.
By specifying 6, the operation of controlling the output value of the average calculation unit 505 to be stored in the output memory 506 is repeated until the brightness values of all the pixels of the enlarged image are obtained.

Next, the operation of this embodiment will be described. Prior to the enlargement of the image, the brightness value of each pixel of the original image is stored in the input memory 501. First, the control unit 507 sequentially designates, as the first read address, the address storing the brightness value of each pixel of the original image in the input memory 501, and at the same time after the original image is enlarged in the output memory 506. Addresses for storing the brightness values of the pixels located are sequentially designated as write addresses. This allows the input memory 5
The luminance value of each pixel of the original image stored in 01 is stored in the output memory 506 as the luminance value of the corresponding pixel after enlargement.

Next, among the pixels of the enlarged image, the four addresses for storing the brightness values of the pixels located at the four corners of the square area and for which the brightness values have already been determined are used as the second read addresses as the output memory 506. And the four brightness values read out by it are input to the intermediate value detecting unit 502, and in the intermediate value detecting unit 502, if the difference between the maximum value and the minimum value is larger than a predetermined threshold value, The maximum value and the minimum value are removed, and the remaining two brightness values are output to the average calculation unit 505. If the difference between the maximum value and the minimum value is less than the threshold value, the four input brightness values are the hues. It is output to the calculation unit 503. If the intermediate value detecting unit 502 outputs the four luminance values to the hue calculating unit 503, the hue calculating unit 50
In 3, the hues of the four input luminance values are obtained, and four pieces of data combined with the input luminance values are output to the intermediate hue detection unit 504.

Next, the intermediate hue detecting unit 504 selects two data having a hue close to the average hue of the four hues out of the four data output from the hue calculating unit 503, and selects from the two selected data. From the luminance value only, the average calculation unit 505
Output to.

Next, the two brightness values output from the intermediate value detecting unit 502 or the intermediate hue detecting unit 504 are averaged by the average calculating unit 505 and output to the output memory 506. Here, the control unit 507 specifies the address for storing the brightness value of the pixel at the center of the square area as the write address in the output memory 506, and the output memory 506 outputs the average value output by the average calculation unit 505 to that address. Memorize The control unit 507 repeats the above operation until the luminance values of all the pixels of the enlarged image are obtained, thereby generating the enlarged image.

As described above, according to the present embodiment, the brightness of the pixel between two pixels is interpolated by using the brightness values of two pixels which are appropriate for the hue even in the portion where the brightness value is little changed by simple calculation. By doing so, it is possible to obtain an enlarged image with little blurring and no large jaggies.

[0027]

As described above, according to the present invention, among the luminance values of the four pixels used for interpolation, the appropriate luminance values of two pixels are selected by a simple process, and the average value is calculated. As a result, it is possible to obtain a magnified image with little blurring of the image and no large jaggies by simple calculation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image enlarging device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing how an enlarged image is generated by the device.

FIG. 3 is a schematic diagram showing an example of an enlarged image obtained by the device.

FIG. 4 is a block diagram showing a configuration of an image enlarging device according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of an image enlarging device in an example of a third example.

FIG. 6 is a block diagram showing a conventional image enlarging device.

[Explanation of symbols]

101 Input memory 102 Intermediate value detector 103 Average calculator 104 output memory 105 control unit 401 input memory 402 Hue calculator 403 Intermediate hue detector 404 Average calculator 405 output memory 406 control unit 501 input memory 502 Intermediate value detection unit 503 Hue calculator 504 Intermediate hue detector 505 Average calculator 506 output memory 507 Control unit

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G06T 3/40 H04N 1/393

Claims (2)

(57) [Claims] 1. An input memory that stores an original digital image and outputs a luminance value of a designated first read address, and the input luminance value by obtaining a hue for each of the four input luminance values. The hue calculation unit that outputs four combined data and the output data of the hue calculation unit are input, and two input data having a hue close to the average hue of the hues of the four input data are selected and the selected input An intermediate hue detection unit that outputs only the brightness value of data, an average calculation unit that outputs the average value of the input values using the output value of the intermediate hue detection unit as an input value, the output value of the input memory or the average calculation The output value of the unit is stored in a specified write address, and when the second read address is specified, an output memory that outputs the value of the specified address to the hue calculation unit; Writing to sequentially specify the first read address storing the brightness value of each pixel of the image stored in the memory, and at the same time store the brightness value of the pixel located after the expansion of each pixel in the output memory. Addresses are sequentially designated, and then the address of the output memory that stores the luminance values of four pixels in the vicinity of the pixel whose luminance value of the enlarged image is undecided is designated as the second read address in the output memory, The operation of controlling the output value of the average calculator to be stored in the output memory by designating the write address for storing the brightness value of the pixel whose brightness value is undecided in the output memory An image enlarging device comprising: a control unit that repeats until the luminance values of all pixels of the image are obtained. 2. An input memory that stores an original digital image and outputs a luminance value of a designated first read address, and a difference between a maximum value and a minimum value from four input luminance values. Is greater than a predetermined threshold value, the two input luminance values excluding the maximum value and the minimum value are output as the first output value, and if the difference between the maximum value and the minimum value is less than the threshold value, An intermediate value detection unit that outputs four input luminance values as second output values, and a second output value of the intermediate value detection unit as inputs, and the hue is obtained for each of the four input luminance values and the input is performed. A hue calculation unit that outputs four data combined with a luminance value, and the output data of the hue calculation unit are input, and two input data having a hue close to the average hue of the hues of the four input data are selected and selected. Output only the brightness value of the input data An intermediate hue detection unit, an average calculation unit that outputs an average value of the input values with the first output value of the intermediate value detection unit or the output value of the intermediate hue detection unit as an input value, and the output of the input memory An output memory that stores a value or an output value of the average calculation unit at a specified write address, and outputs a value of the specified address to the intermediate value detection unit when a second read address is specified. ,
A first read address that stores the brightness value of each pixel of the image stored in the input memory is sequentially specified, and at the same time, the brightness value of the pixel where each pixel is located after expansion is stored in the output memory. Write addresses are sequentially specified, and then the address of the output memory that stores the brightness values of four pixels in the vicinity of the pixel whose brightness value of the enlarged image is undecided is specified as the second read address in the output memory. Then, the operation of controlling to store the output value of the average calculation unit in the output memory by designating the write address for storing the luminance value of the pixel whose brightness value is undecided in the output memory is enlarged. An image enlarging device, comprising: a control unit that repeats until the luminance values of all pixels of a subsequent image are obtained.