JP3585036B2 - Image generation method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image creation method, an image creation apparatus, and a program, and particularly to a technique for preventing useless pixel information from being included in a pixel information table when a reduced-color original image is generated from an original image including pixels having transparency. About.
[0002]
[Prior art]
The image expression method called full color associates each pixel with 32-bit pixel information. The color of each pixel is specified by 24 bits (for example, three color components (RGB) are specified by each 8 bits). ), And the transparency is often specified by the remaining 8 bits. According to this method, 2 ³² It is possible to arbitrarily associate each type of pixel information with each pixel. ³² Type of pixel information (2 ²⁴ Color and 2 ⁸ Level of transparency) can be displayed at the same time, so that the image quality can be kept at the highest.
[0003]
However, a full-color image has an enormous amount of data and has many practical problems. Therefore, in an image expression method called 8-bit color, for example, 2 bits ³² 2 out of the types of pixel information ⁸ An image is represented by selecting the type and associating the limited pixel information with each pixel. According to this method, pixel information that can be displayed simultaneously is 2 ⁸ Although the number of data types can be reduced, the data amount can be significantly reduced without significantly reducing the image quality.
[0004]
[Problems to be solved by the invention]
However, in the 8-bit color format, if the image to be expressed partially includes transparency, ³² Efficiently from 2 types of pixel information ⁸ There is a problem that it is very difficult to select the type of pixel information. For example, 2 so that all colors can be displayed with the same level of transparency ⁸ When the type of pixel information is selected, usually, there are many colors that do not require transparency, so that a lot of useless (not actually displayed) pixel information is selected. Therefore, it is desirable not to select useless pixel information so that more colors are simultaneously displayed for opaque pixels.
[0005]
The present invention has been made in view of the above problems, and its purpose is to generate transparency-reduced original images from original images including pixels having transparency, by setting transparency to colors that do not require transparency. It is an object of the present invention to provide an image creation method, an image creation device, and a program that can prevent the image creation.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, an image creating method according to the present invention is based on an original image in which any one of a first type of pixel information including color information and transparency information is associated with each pixel. An image generation method for generating a reduced-color original image in which any one of the second type number of pieces of pixel information smaller than the first type number, which includes color information and transparency information, is associated with each pixel. An image region dividing step of dividing the original image into a transparent region image composed of pixels having transparency, and an opaque region image composed of pixels having no transparency, and a pixel associated with each pixel of the opaque region image An opaque region image color reduction step of reducing information to a third type number smaller than the second type number to generate a reduced color opaque region image; and correlating with each pixel of the transparent region image. A transparent area image color reduction step of reducing the pixel information obtained to a fourth type number obtained by subtracting the third type number from the second type number to generate a reduced color transparent area image; and A combining step of generating the reduced-color original image based on the reduced-color transparent area image.
[0007]
In addition, the image creating apparatus according to the present invention is configured to provide color information and transparency information based on an original image in which any one of the first type of pixel information including color information and transparency information is associated with each pixel. In the image generating apparatus for generating a reduced-color original image in which each of the pieces of pixel information of the second type smaller than the first type number, each of which includes Means for dividing into a transparent area image composed of pixels having the following formula, and an opaque area image composed of pixels having no transparency, and pixel information associated with each pixel of the opaque area image is obtained from the second number of types. Means for generating a color-reduced opaque region image by reducing the number of third types to a smaller number, and converting the pixel information associated with each pixel of the transparent region image from the second type number to the third type number. Pulled Means for generating a reduced-color transparent area image by reducing the number of types to four, and means for generating the reduced-color original image based on the reduced-color opaque area image and the reduced-color transparent area image. Features.
[0008]
Further, the program according to the present invention, based on an original image in which any one of the first type of pixel information respectively including the color information and the transparency information is associated with each pixel, the color information and the transparency information respectively Is a program for generating a reduced-color original image in which any one of pixel information of a second type smaller than the first type is included in each pixel. An image area dividing step of dividing the image into a transparent area image composed of pixels having the following formula, and an opaque area image composed of pixels having no transparency. An opaque region image color reduction step of generating a reduced color opaque region image by reducing the number of types to a third type smaller than the number of types, and pixel information associated with each pixel of the transparent region image; A transparent area image color reduction step of generating a reduced color transparent area image by subtracting the third number from the second number to generate a reduced color transparent area image; the reduced color opaque area image and the reduced color transparent area image And a synthesizing step of generating the color-reduced original image based on the above.
[0009]
Here, the color information is information representing the color of each pixel, and can be configured by combining information representing the component amounts of colors such as red (R), green (G), and blue (B). In this case, the color information is also called “RGB value”, for example, black is represented by (R, G, B) = (0, 0, 0), and (R, G, B) = (255, 0, 0) ) Represents red. The transparency information is information indicating the transparency of each pixel, and is called, for example, “alpha” or “alpha channel”. The transparency information is expressed by, for example, a ratio of the intensity of light projected on a certain pixel portion to the intensity of light transmitted through the pixel portion.
[0010]
In the present invention, first, an original image in which any one of the first type of pixel information is associated with each pixel is prepared. Then, the original image is divided into a transparent area image and an opaque area image. The transparent area image is an image composed of pixels to which pixel information including transparency information indicating that the transparency is greater than zero, that is, not opaque, is associated. The opaque area image is an image composed of pixels associated with pixel information including transparency information indicating that the transparency is zero, that is, opacity. Next, the pixel information associated with each pixel of the transparent area image is reduced to a third type number, and the pixel information associated with each pixel of the opaque area image is reduced to a fourth type number. Thereafter, a reduced-color original image is generated based on the reduced-color transparent area image and the reduced-color opaque area image thus obtained. The reduced-color original image is an image in which one of the second type of pixel information is associated with each pixel. Note that the first type number is larger than the second type number, and the number obtained by adding the third type number and the fourth type number is equal to the second type number.
[0011]
In the present invention, since the color of the transparent area image and the color of the opaque area image are separately reduced, it is possible to prevent the transparency from being set to a color that does not require transparency, and to efficiently reduce the color of the original image. be able to. Also, by changing the ratio of the number of types of pixel information associated with each pixel of the reduced-color transparent area image and the number of types of pixel information associated with each pixel of the reduced-color opaque area image, for example, the opaque area The user can arbitrarily set whether to emphasize the number of colors or the number of levels of transparency of the transparent area. Therefore, appropriate color reduction processing can be performed on the original image according to the purpose of use of the reduced color original image and the content of the original image.
[0012]
Further, in one aspect of the present invention, the transparent area image color reduction step (means for generating a reduced color transparent area image) includes a background image in which pixel information including color information corresponding to a predetermined color is associated with all pixels. Generating a transparent area image with a background by translucently combining the transparent area image (means), and reducing the pixel information associated with each pixel of the transparent area image with a background to the fourth type number (Means) generating a transparent area image with a reduced color background by using a transparent area corresponding to a difference between a color of each pixel of the transparent area image with a reduced color background and the predetermined color. Generating the reduced-color transparent area image by setting the transparency information included in the pixel information associated with each pixel of the image (means).
[0013]
That is, in the color-reduced background-added transparent area image, the larger the difference between the color of each pixel and the color of the background image (the closer the pixel color is to the color of the pixel), the more the corresponding pixel in the original transparent area image It can be determined that a lower transparency is set for the corresponding pixel in the original transparent area image, as the difference is smaller (the color of the pixel has a color closer to the color of the background image). Can be determined to have been set, in this embodiment, the transparency corresponding to the difference between the color of each pixel of the reduced-color background-transparent area image and the color of the background image is calculated as the transparency of each pixel of the reduced-color background-transparent area image. It is set in transparency information. According to this aspect, the reduced-color transparent area image can be generated without requiring special image processing software or the like.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0015]
An image creating method according to an embodiment of the present invention is implemented using a known personal computer system including a display 10, a CPU (Central Processing Unit) 12, a mouse 14, and a keyboard 16, as shown in FIG. Is done. Here, known image processing software having a color reduction function is installed in the CPU 12 using an information storage medium such as a CD-ROM (Compact Disk-Read Only Memory; trademark). With the software, the user can perform arbitrary image processing on the original image prepared in advance by using the mouse 14 and the keyboard 16. Here, a method of converting a full-color original image into an 8-bit color-format texture image will be described.
[0016]
FIG. 2 is a flowchart illustrating a procedure of an image creating method according to an embodiment of the present invention, and FIG. 3 is a flowchart illustrating the process of S104 in FIG. 2 in detail. FIG. 4 is a flowchart illustrating the process in S106 of FIG. 2 in detail.
[0017]
As shown in FIG. 2, when creating an 8-bit color texture image, first, a user creates an arbitrary full-color original image (full-color original image) (S101). In a full-color original image, 32-bit pixel information is associated with each pixel. The pixel information includes 24-bit color information that specifies red, green, and blue color components, and 8-bit transparency information that specifies transparency. FIG. 5 shows an example of the full-color original image created in S101. The full-color original image 20 shown in FIG. 1 includes a transparent area 22 and an opaque area 24. The transparent area 22 is an image area having transparency (greater than zero), that is, non-opaque pixels. The opaque region 24 is an image region having no transparency, that is, an image region including opaque pixels, and is a portion other than the transparent region 22.
[0018]
Next, the user arbitrarily determines the number n of pixel information types of the transparent area image and the number m of pixel information types of the opaque area image (S102). Here, the sum of the pixel information types n and m is 2 ⁸ (= 256).
[0019]
Then, the original image created in S101 is divided into a transparent area image and an opaque area image (S103). The transparent area image has the same size as the original image, and is made up of pixels included in the original image having transparency, that is, pixels associated with transparency information indicating that the image is not opaque. The opaque area image has the same size as the original image, and includes pixels having no transparency among the pixels included in the original image, that is, pixels to which transparency information indicating that the image is opaque is associated. You.
[0020]
6 and 7 show an example of the transparent region image and the opaque region image obtained in this step. The transparent area image 26 shown in FIG. 6 is an image divided (separated and extracted) from the full-color original image 20 and has a full-color format. The transparent area image 26 has the same size as the full-color original image 20, and the transparent area 22 included in the full-color original image 20 is shown as it is. Then, for example, white opaque pixel information is given to the pixels in the remaining area 28.
[0021]
The opaque area image 32 shown in FIG. 7 is also an image obtained by dividing (separating and extracting) the full-color original image 20 and has a full-color format. The opaque area image 32 also has the same size as the full-color original image 20, and the opaque area 24 included in the full-color original image 20 is represented as it is. For example, colorless and transparent pixel information is assigned to the pixels in the remaining area 30.
[0022]
Next, the color of the transparent area image is reduced to the pixel information type number n (S104). When the color reduction function of the above-mentioned known image processing software is used, specifically, as shown in FIG. 3, first, a transparent region image is translucently combined with a background image (S104a). The background image is the same size as the original image, and is a monochrome and opaque image. It is desirable to determine the color of the background image with reference to the color tone of the image that will actually be used as the background of the transparent area image. For example, when it is assumed that a dark image is used as the background, it is desirable to adopt a black and opaque image as the background image. When it is assumed that a whitish image is used as the background, it is desirable to adopt a white and opaque image as the background image. Thus, a background-added transparent area image in which all pixels are opaque is obtained. In this transparent area image with background, pixels associated with greater transparency in the transparent area image have a color closer to the color of the background image.
[0023]
FIG. 8 shows an example of the background image, and FIG. 9 shows an example of the transparent area image with the background. The transparent area image 38 with the background shown in FIG. 9 has a full color format, and is obtained by translucently combining the transparent area image 26 shown in FIG. 6 with the background image (full color format) 34 shown in FIG. is there. In the background-added transparent area image 38, all pixels are opaque. Here, the transparent region with background 36 of the transparent region image with background 38 corresponds to the transparent region 22 in the transparent region image 26, and the transparent region with background 36 according to the transparency of each pixel included in the transparent region image 26. The color of the background image 34 is added to each pixel included in. That is, if the transparency of each pixel included in the transparent region 22 is large (high), the pixel included in the transparent region with background 36 becomes closer to the color of the background image 34, and the transparency of each pixel included in the transparent region 22 is reduced. If it is small (low), it will be closer to the color of the pixel information set for the pixel.
[0024]
Next, the color of the background-added transparent area image is reduced to the pixel information type number n (S104b). Many methods are already known as color reduction processing by software, but color reduction may be performed by any method. An image obtained by this color reduction processing, that is, a transparent area image with a reduced color background includes n types of pixel information. FIG. 10 shows an example of a pixel information table (CLUT; Color Look Up Table) generated by the color reduction processing. FIG. 7 shows a pixel information table obtained when the pixel information associated with the pixels of the background-added transparent area image is reduced to 128 types. When drawing a transparent area image with a background, the shaded portions in the drawing are not referred to, and the portions denoted by reference symbols A (color information) and B (transparency information) in FIG. Only the pixel information of 1 to 128 is referred to.
[0025]
Next, the pixel information included in the pixel information table generated in S104b is rearranged in ascending order of the color represented by the color information included in the pixel information table (S104c). Then, n levels of transparency (ie, the same number as the number n of pixel information types of the background-added transparent area image) are set in the transparency information column of the pixel information table according to the order of rearrangement. That is, the closer the color represented by the color information included in the pixel information is to the color of the background image, the greater the transparency is set to the transparency information included in the pixel information (S104d). This is because it can be determined that the closer the color assigned to each pixel of the background-added transparent region image to the color of the background image, the higher the transparency (larger transparency) is given to the original transparent region image. It is. The transparency setting and the color-reduced background-added transparent area image thus obtained are used as the color-reduced transparent area image in the subsequent processing (specifically, the processing of S106).
[0026]
Returning to FIG. 2, next, the color of the opaque area image obtained in S103 is reduced to the number m of pixel information types (S105). For the color reduction processing, any known method can be adopted. FIG. 11 shows an example of a pixel information table generated by the color reduction processing. FIG. 3 shows a pixel information table obtained when the pixel information associated with the pixels of the opaque area image is reduced to 128 types. When drawing an opaque area image, the hatched portions in the figure are not referred to, and the portions denoted by reference symbols C (color information) and D (transparency information) in FIG. Only the pixel information relating to 129 to 256 is referred to.
[0027]
Thereafter, the reduced color original image, that is, the 8-bit color format, is synthesized by combining the reduced color transparent region image (transparency setting and the reduced color background-added transparent region image) obtained in S104 and the reduced color opaque region image obtained in S105. Is generated (S106). Specifically, as shown in FIG. 4, first, the pixel information table obtained in S104 and the pixel information table obtained in S105 are combined (S106a). 12 shows a pixel information table (obtained in S104) shown in FIG. 10 and a pixel information table (obtained in S105) obtained by synthesizing the pixel information table (obtained in S105) shown in FIG. Table) is shown. In step S106a, the pixel information No. in the pixel information table obtained in step S104. Pixel information Nos. 129 to 256 (shaded portions in FIG. 11) are added to the pixel information No. of the pixel information table obtained in S105. By overwriting 129 to 256, a combined pixel information table is obtained.
[0028]
After that, the reduced-color transparent area image (transparency setting and reduced-color transparent background-added image) is combined with the reduced-color opaque area image to generate a reduced-color original image (S106b). FIG. 13 shows a reduced color original image obtained by combining the image obtained by performing the color reduction processing on the opaque area image 32 shown in FIG. 7 with the transparent area image 38 with the background shown in FIG. I have. In the reduced-color original image shown in the figure, the pixel information of the remaining area 30 of the opaque area image 32 is replaced with the pixel information of the transparent area with background 36 in the transparent area image 38 with transparency (with transparency set and reduced in color). ing.
[0029]
When the reduced color original image is generated as described above, the number of types of pixel information can be separately specified for the transparent region and the opaque region in the original image, and the color reduction processing can be performed separately. The image quality can be arbitrarily allocated to the transparent region and the opaque region by increasing the number or the number of transparent steps of the transparent region.
[0030]
In the above description, the user manually converted the original image into the color-reduced original image using the image processing software. However, by executing the dedicated color reduction program on the personal computer system shown in FIG. The color reduction processing may be automated by causing the system to function as an image creating apparatus capable of generating a reduced-color original image of the image quality.
[0031]
FIG. 14 is a diagram showing functions realized when the dedicated color reduction program is executed by the personal computer system shown in FIG. As shown in the figure, the functions realized by the personal computer include an original image input unit 50, an area division unit 52, a transparent area image color reduction unit 54, an opaque area image color reduction unit 56, and the number of types of pixel information. A setting unit 58 and an image synthesizing unit 60 are included.
[0032]
The original image input unit 50 is a functional block for inputting, for example, an original image (original image data) in a full-color format. For example, the original image input unit 50 receives an image file created by known image processing software or an image file photographed by various imaging devices. The user can arbitrarily specify the image file by using the mouse 14 or the keyboard 16 to input the image file to the area dividing unit 52 as an original image.
[0033]
The region dividing unit 52 divides the original image input from the original image input unit 50 into a transparent region image and an opaque region image. The transparent area image is input to the transparent area image color reduction section 54, and the opaque area image is input to the opaque area image color reduction section 56. The pixel information type number setting unit 58 is used by the user to set the number n of types of pixel information used in the transparent area image and the number m of types of pixel information used in the opaque area image by using the mouse 14 or the keyboard 16, for example. Is a functional block. The number n of types is input to the transparent area image color reduction section 54, and the number m of types is input to the opaque area image color reduction section 56. When generating an 8-bit color reduced original image, the user sets each value so that the sum of m and n becomes 256.
[0034]
The transparent area image color reduction unit 54 generates a reduced color transparent area image by reducing the pixel information used in the transparent area image input from the area division unit 52 to n types. A known color reduction algorithm can be used for the color reduction processing here. For example, a four-dimensional pixel information space having four axes respectively corresponding to a red component, a blue component, a green component, and transparency is prepared on a memory of a personal computer, and all pixel information used in a transparent area image is stored in the same space. To plot. Then, each point is divided into n groups of those having a short distance in the same space. Further, pixel information corresponding to, for example, the position of the center of gravity of a point belonging to each group is set as representative pixel information of the group. Then, the pixel information of the transparent area image before the color reduction corresponding to the points belonging to each group is replaced with the representative pixel information of the group. By doing so, the pixel information of the transparent area image input from the area dividing unit 52 can be reduced to n types. The reduced color transparent area image generated by the transparent area image color reduction section 54 is input to the image synthesis section 60.
[0035]
The opaque region image color reduction unit 56 generates a reduced color opaque region image by reducing the pixel information of the opaque region image input from the region dividing unit 52 to m types. A well-known color reduction algorithm may be used for the color reduction processing here as well as the above. The color-reduced opaque area image generated by the opaque area image color reducing section 56 is also input to the image synthesizing section 60.
[0036]
The image combining unit 60 combines the reduced color transparent image input from the transparent region image color reducing unit 54 with the reduced color opaque image input from the opaque region image color reducing unit 56 to convert the reduced color original image. Generate.
[0037]
In this manner, the color reduction processing of the original image can be automated. At this time, the number of types of pixel information can be separately specified for the transparent area image and the opaque area image by the pixel information type number setting unit 58, so that the image quality can be arbitrarily adjusted according to the use and contents of the image. can do.
[0038]
【The invention's effect】
As described above, according to the present invention, when generating a reduced color original image based on the original image, the original image is divided into a transparent region image and an opaque region image, and the reduced opaque region image is converted from the opaque region image. As well as generating a reduced-color transparent area image from the transparent area image, and generating a reduced-color original image based on the reduced-color opaque area image and the reduced-color transparent area image. It is possible to prevent the transparency from being set for colors that are not used, and to improve the image quality.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an external appearance of a computer system that executes an image creating method according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a procedure of an image creating method according to the embodiment of the present invention.
FIG. 3 is a flowchart illustrating a color reduction procedure for a transparent area image.
FIG. 4 is a flowchart illustrating a procedure for synthesizing a reduced-color transparent area image and a reduced-color opaque area image.
FIG. 5 is a diagram illustrating an example of an original image.
FIG. 6 is a diagram illustrating an example of a transparent area image.
FIG. 7 is a diagram illustrating an example of an opaque area image.
FIG. 8 is a diagram illustrating an example of a background image.
FIG. 9 is a diagram illustrating an example of a transparent area image with a background.
FIG. 10 is a diagram illustrating an example of a pixel information table obtained by performing a color reduction process on a transparent area image.
FIG. 11 is a diagram illustrating an example of a pixel information table obtained by color reduction processing of an opaque area image.
12 is a diagram showing a combined pixel information table obtained by combining the pixel information table shown in FIG. 10 and the pixel information table shown in FIG. 11;
FIG. 13 is a diagram illustrating an example of a reduced-color original image.
FIG. 14 is a diagram showing functional blocks of the image creating apparatus according to the embodiment of the present invention.
[Explanation of symbols]
10 display, 12 CPU, 14 mouse, 16 keyboard, 20 full color original image, 22 transparent area, 24 opaque area, 28, 30 residual area, 34 background image, 36 transparent area with background, 38 transparent area image with background, 40 color reduction A completed original image, a 50 original image input unit, a 52 region division unit, a 54 transparent region image color reduction unit, a 56 opaque region image color reduction unit, a 58 pixel information type setting unit, and a 60 image synthesis unit.

Claims (1)

Based on an original image in which any one of the first type of pixel information respectively including the color information and the transparency information is associated with each pixel, the first type number including the color information and the transparency information respectively is used. An image generating method for generating a reduced-color original image in which any one of the second type of pieces of pixel information having a smaller number is associated with each pixel,
The original image, a transparent region image composed of pixels having transparency, and an opaque region image composed of pixels having no transparency, an image region dividing step of dividing,
An opaque area image color reduction step of reducing the pixel information associated with each pixel of the opaque area image to a third type number smaller than the second type number to generate a reduced color opaque area image;
A transparent area image for generating a reduced-color transparent area image by reducing the pixel information associated with each pixel of the transparent area image to a fourth type number obtained by subtracting the third type number from the second type number A color reduction step,
A combining step of generating the reduced color original image based on the reduced color opaque area image and the reduced color transparent area image,
Including
The transparent area image color reduction step,
A step of translucently synthesizing the transparent area image with a background image corresponding to all pixels with pixel information including color information corresponding to a predetermined color to generate a background-added transparent area image,
Reducing the pixel information associated with each pixel of the background-added transparent region image to the fourth type to generate a reduced-color background-added transparent region image;
The transparency corresponding to the difference between the color of each pixel of the reduced-colored background-added transparent area image and the predetermined color is included in the transparency information included in the pixel information associated with each pixel of the reduced-colored background-added transparent area image. Setting, generating the reduced color transparent area image,
An image generation method comprising:

Images