JPH07262347A - Image processor - Google Patents

Abstract

PURPOSE:To automatically adjust lightness into natural lightness corresponding to a converted hue. CONSTITUTION:Concerning the image processor for enabling hue conversion by providing an image data input part 2, hue converting part 10 and image data output part 4, this device is equipped with a lightness adjusting table 12 for which the lightness before the adjustment is made correspondent to the lightness after the adjustment so that the lightness of hue converted image data can be adjusted into any suitable lightness, and a lightness converting part 11 for converting the lightness of image data while referring to the lightness adjusting table 12. Thus, the hue of hue converted image data is adjusted into any suitable lightness and outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for performing color image processing on color photographs, paintings and the like.

For color printing and the like, development of an image processing apparatus that uses a computer to perform color image processing is in progress. Such a color image processing apparatus can perform color editing such as hue conversion by designating a color to be changed and a color after the change on the screen.

[0003]

2. Description of the Related Art FIG. 8 shows a conventional image processing apparatus. Figure 8
In the figure, 200 is an image before conversion.

Reference numeral 201 denotes an image block before conversion,
For example, it is a collection of 8 × 8 pixels. 200 'is the image after conversion.

Reference numeral 201 'is an image block after conversion.
205 is an image processing apparatus. Reference numeral 206 denotes a conversion instructing unit, which instructs hue conversion such as designation of a hue to be converted (for example, converting a red hue into a yellow hue).

210 is an image data input unit for inputting image data of each pixel of the image 200. Each pixel has coordinates (L ^* , a ^* , b ^* ) in the uniform color space coordinate system. L ^* is lightness, and a ^* and b ^* are colors (hue /
Represents the saturation.

Reference numeral 211 denotes a hue conversion unit, which is L ^* a ^* b
^* The color (a ^* , b ^* ) of the coordinate system is converted into the hue H of the Munsell coordinate system (described later), and the hue of the input image data is included in the area of the designated hue for conversion. If it is included in the area of the specified hue, the converted hue H is rotated to be the converted hue H ′, and the hue H ′ is the color of the a ^* b ^* coordinate system ( a ^* ', b
^* ').

An image data output unit 212 outputs the converted image data. As shown in the configuration of FIG. 8, the conventional image processing apparatus converts only the hue, and the lightness is not changed before and after the conversion.

FIG. 9 is an explanatory diagram of hue conversion of a conventional image processing apparatus. FIG. 9A is an explanatory diagram of hue conversion of the conventional image processing apparatus. The hue before changing the operator instruction is Ho
rg, its hue angle is Rorg, and the changed hue is Hch
g, and its hue angle is Rchg, H ′ after rotation with respect to H before rotation is H = Hchg− (Horg−H) ×
It is calculated by (Rchg / Rorg).

[0010]

The problem to be solved by the invention will be described with reference to FIG. 9 (b). In FIG. 9B, the a ^* axis represents hue (the greater a ^{*, the} higher the saturation), and the vertical axis represents the lightness L ^* . FIG. 9B shows the lightness distribution of the yellow hue. The lightness of the yellow hue is distributed as shown in the figure, and it is shown that the lightness is not uniformly distributed over the entire yellow hue space.

If the converted hue H ₀ 'in FIG. 9 (a) is a yellow hue and is converted to the coordinate Y in FIG. 9 (b), it is in the yellow lightness distribution region. Because of this, the converted hue is natural, but when converted into Y ', it has an unrealistic lightness and is therefore unnaturally expressed.

It is an object of the present invention to provide an image processing apparatus which automatically adjusts the lightness to a lightness that is not unnatural according to the converted hue.

[0013]

FIG. 1 shows the basic configuration of the present invention. In FIG. 1, reference numeral 1 is an image processing apparatus.

Reference numeral 2 is an image data input section for inputting image data before conversion. An image data output unit 4 outputs the converted image data. Reference numeral 5 denotes a conversion instructing unit for designating a hue to be converted and a hue after conversion.

Reference numeral 10 denotes a hue conversion unit, which converts the hue of image data. Reference numeral 11 denotes a lightness conversion unit, which refers to the lightness adjustment table 12 and converts the lightness of the image data.

A lightness adjustment table 12 associates the lightness before adjustment with the lightness after adjustment so that the converted hue is adjusted to a lightness that is not unnatural. The correspondence between the brightness before adjustment and the brightness after adjustment is performed by, for example, providing a conversion formula or a conversion table in which the brightness before adjustment and the brightness after adjustment are associated with each other.

[0017]

The operation of the basic configuration of the present invention shown in FIG. 1 will be described. The image data input unit 2 inputs the image data before conversion for each pixel. The hue conversion unit 10 determines whether or not the hue of the input pixel is included in the hue of the conversion-designated area, and if the hue is included in the conversion-designated hue area, the specified hue is determined. Convert to.

The lightness conversion unit 11 determines the lightness (luminance) of the pixel whose hue has been converted, refers to the lightness adjustment table 12, and refers to the conversion formula or the conversion data of the lightness of the converted hue. Then, the conversion is performed according to the brightness conversion formula or conversion table.

The image data output unit 4 outputs the converted image data of hue and lightness. According to the present invention, the hue-converted image data is converted into a natural lightness determined according to each hue, so that a visually converted image can be obtained.

[0020]

FIG. 2 is a diagram showing the configuration of an embodiment of the present invention.
Figure 2 shows the coordinates of the L ^* a ^* b ^* coordinate system (L ^* , a ^* , b ^* ).
The configuration of an embodiment in the case of performing the hue conversion (H conversion) of the hue angle H (0 to 360 °) of (a ^* , b ^* ) of No.

In FIG. 2, reference numeral 40 denotes an RGB data input section, which is an image scanner, an image pickup device or the like.

Reference numeral 41 is a color conversion unit 1 for converting RGB data into lightness and hue (L ^* , a ^* , L ^* a ^* b ^* coordinate system ⁾ .
b ^* ). Reference numeral 42 denotes a color conversion unit 2, which is a lightness and hue (L ^* , a ^* , b) of the L ^* a ^* b ^* coordinate system.
^* ) Is converted into RGB data or YMC data (data for print output).

Reference numeral 43 is a display. Reference numeral 44 is a printing device. An image processing device 50 converts the hue and lightness of image data.

Reference numeral 51 is an image data input section. An image data holding unit 52 holds the image data before conversion and the image data after conversion.

Reference numeral 52 'is image data before conversion. 52 "
Is the converted image data. Reference numeral 54 is an image data output unit.

Reference numeral 55 is a conversion instruction section. Reference numeral 60 is a hue conversion unit. Reference numeral 61 is a lightness conversion unit.

Reference numeral 62 is a brightness adjustment table. Reference numeral 70 represents image data (L ^* , a ^* , b ^* ) before conversion. Reference numeral 71 is H-converted image data (H, L ^* ).

Reference numeral 72 denotes coordinates (H ', L ^* ) whose hue has been converted by rotating the hue H in the Munsell coordinate system. 7
Reference numeral 3 denotes image data (H ', L ^* ) in the Munsell coordinate system whose lightness has been converted with reference to the lightness adjustment table 62.

Reference numeral 73 'is image data (H, L ^* ) which has not been subjected to hue conversion. 74 uses (H ', L ^* ) as L ^* a ^*
It is converted to (L ^* ', a ^* ', b ^* ') in the b ^* coordinate system.

The operation of the configuration of FIG. 2 will be described later. FIG. 3 is an explanatory diagram of the relationship between hue and maximum brightness. FIG. 3 (a) is a graph showing the relationship between the hue and the maximum lightness, by finding the lightness value of the maximum saturation in each hue with reference to the standard color chart and color table. FIG. 3 (b) is a table showing the relationship between the hue and the maximum lightness.

As shown in the graph of FIG. 3 (a) and the table of FIG. 3 (b), the relationship between the hue and the maximum lightness is not uniform and varies depending on the hue. Therefore, it is necessary to convert the lightness of the hue converted in consideration of the maximum value of the lightness of each hue before and after the conversion.

For example, consider a case where the hue H = 92 is changed to the hue H = 358. Hue H = 92 has maximum brightness of 184
With. On the other hand, the hue H = 358 has the maximum lightness of 79.
Therefore, in the present invention, for example, the hue H = 92 is changed to the hue H = 3.
When changing to 58, the maximum brightness values 184 and 7
In consideration of 9, the lightness of the hue after conversion is also converted according to the maximum lightness.

FIG. 4 is an explanatory view of the method of creating the brightness adjustment table of the present invention. FIG. 4 (a) shows the case of conversion formula. Lightness L (hereinafter, lightness is also expressed as L in H conversion)
The maximum brightness 255 is converted to the maximum brightness 255, and the minimum brightness 0 (black) is converted to the minimum brightness 0 in the H conversion from the lightness to the lightness L ′. Then, the lightness L0 and L1 are obtained. Then, for L0 and L1, if (1) L ≦ L0,
L ′ = (L1 / L0) × L, (2) When L> L0,
L'is converted into L'by L '= 255-{(L1 / L0) * (255-L)}. In addition, L0, L
1 is different depending on the hue.

FIG. 4 (b) shows 0 to 255 of the conversion formula of FIG. 4 (a).
It is a table of L'for L of. The brightness conversion is
The calculation is performed by the conversion formula as described above, or a conversion table in which the lightness L before conversion and the lightness L ′ after conversion are associated is created, and conversion is performed according to the conversion table. If the conversion table is used, the processing speed is increased.

The conversion formula or conversion table of FIG. 4 is created for each hue or each hue group. FIG. 5 is a diagram showing an example of the brightness adjustment table of the present invention. FIG. 5 (a) shows a modification method 1, which is a case of linear conversion (similar to FIG. 4 (a)). L0 and L1 are experimentally obtained so that the converted lightness is natural. 0 ≦ L ≦ L for lightness L before change
In the case of 0, the lightness is converted according to the formula of the graph k1, and L
When 0 <L ≦ 255, the lightness is converted according to the equation of the graph k2. The graph may be converted into a conversion table and converted according to the table.

(B) is a case of nonlinear conversion. As shown in the figure, the pre-change L is converted to the post-change L'by a conversion formula represented by a non-linear graph. The graph may be a conversion table and conversion may be performed according to the table.

(C) shows a case where the highlight point or the gray point is changed in the non-linear conversion.
The solid line (k1) is for changing the gray point to a brighter one, and the dotted line (k2) is for changing the highlight point. The graph may be converted into a conversion table and converted according to the table.

The operation of the embodiment of the present invention shown in FIG. 2 will be described. The color conversion unit 1 (41) receives R from the RGB data input unit 40.
Enter the GB data and enter the coordinates in the L ^* a ^* b ^* coordinate system (L
^* , A ^* , b ^* ). The image processing apparatus 50 inputs the image data converted by the color conversion unit 1 (41) for each pixel and performs hue conversion and lightness conversion.

In the image processing apparatus 50, the image data input section 51 takes out the image data converted into the L ^* a ^* b ^* coordinate system from the color conversion section 1 (41) and stores it in the image data holding section 52. .

Next, the operation of the hue / brightness converter will be described with reference to FIG. 6 (see FIG. 2). The S1 color conversion unit 60
It is determined whether or not all pixels have been taken out. If all pixels have been taken out, the process proceeds to S8, and if not, the process proceeds to S2.

The S2, S3 hue conversion unit 60 converts the pixels (L ^* , a ^* , b ^* ) of the image data into the image data holding unit 52.
Take out from. Extracted image data (L ^* , a ^* , b
^* ) (70) is H-converted to obtain H-converted image data (H, L ^* ) (71).

It is determined whether S4, S4 'H is the target area, and H
If it is outside the area, it is changed to the original (L ^* , a ^* , b ^* ) (7
4) and stores it as converted image data 52 ″ in the image data holding unit 52. If it is within the target area, the process proceeds to S5.

The S5 H converted image data (71) is rotated to obtain the rotated coordinate data (H ', L ^* ) (72). In this processing, the hue before the change of the operator instruction is Horg, the hue angle thereof is Rorg, and the hue after the change is Horg.
chg and its hue angle is Rchg (see FIG. 9),
H'after rotation with respect to H before rotation is H = Hchg- (H
org-H) * (Rchg / Rorg).

S6 The lightness conversion unit 61 refers to the hue conversion formula or conversion table corresponding to H'of the lightness adjustment table 62 by H'of the conversion unit, and based on L ^* (L of the conversion adjustment table) The converted lightness L ^* is obtained.

S7 The image data (H ', L ^* ) in the Munsell coordinate system whose hue and lightness have been converted into the image data (L ^* ', a ^* ', b ^* ') in the L ^* a ^* b ^* coordinate system. The converted image data is stored in the image data holding unit 52 as the converted image data 52 ″.

S8 After processing all the image data, the image data output unit 54 outputs the converted image data to the color conversion unit 2 (42). The color conversion unit 2 (42) converts it into RGB data and outputs it to the display 43. Also, YMC
The data is converted and output to the printing device.

FIG. 7 shows an embodiment of the hue conversion section of the image processing apparatus of the present invention. L ^* a ^* b ^* coordinate system of a ^*, hue b ^* range taken by the when the 0 to 255 each area to be converted in advance (a ^*, b ^*) from the ^{(a * ', b *'} ) Create a conversion table, and use (a ^* , b ^* ) to (a ^* ',
By performing the conversion into b ^* ') by referring to the hue conversion table, the processing speed can be increased.

FIG. 7 shows an embodiment of the hue conversion section in such a case. In FIG. 7, reference numeral 61 is a lightness conversion unit.

Reference numeral 62 is a brightness adjustment table. Reference numeral 80 is a hue conversion unit. Reference numeral 81 is the input image data.

Reference numeral 82 denotes an area determination unit which determines whether or not the input image data 81 is within the designated conversion area. A hue conversion table reference unit 83 refers to the hue conversion table 84 when the image data is inside the conversion area, and obtains the hue after conversion.

Reference numeral 84 is a hue conversion table, which is before conversion
Hue of (a^*, B^*) Corresponding to the converted hue
(A^*’, B^*′) As a control table
It Reference numeral 85 is image data after conversion. However, image day
(L^*, A^*, B^*) (81) is the hue outside the conversion area
If there is, the image data (L^*, A^*, B ^*)
It is the same as (81).

In the configuration of FIG. 7, the hue conversion section 80 takes in the image data (L ^* , a ^* , b ^* ) (81) from the image data holding section (not shown (see FIG. 2)). The area determination unit 82 determines whether the captured image data is within the designated conversion area, and the determination result is used as the hue conversion table reference unit 8
Notify 3. If the fetched image data (L ^* , a ^* , b ^* ) (81) is within the area designated for conversion, the hue conversion table reference unit 83 refers to the hue conversion table 84 to convert the image of the hue to be converted. Data (a ^* ', b ^* ') is taken out and image data (L ^* , a ^* 'b ^* ') (85)
Is acquired and transferred to the brightness conversion unit 61. If the conversion is outside the specified area, the captured image data (L ^* , a
^* , B ^* ) (81) is transferred to the brightness conversion unit 61 as it is.

The lightness conversion section 61 refers to the lightness conversion formula or the conversion data of the lightness adjustment table 62 corresponding to the hue of the received image data, obtains the conversion data L ^* 'of the lightness L ^* , and obtains the image data (L ^* ', A ^* , b ^* ) or (L ^* ', a ^* ', b ^* ') is output to the image data holding unit.

[0054]

According to the present invention, when the color of the image data is changed in the image processing apparatus, the operator simply designates the color before the change and the color after the change to easily obtain the converted hue. It is possible to obtain a color having a natural brightness corresponding to the color. Therefore, it becomes easy to obtain an appropriate color in the color editing process. Further, by using the conversion table in which the conversion data is associated with the hue conversion and the lightness conversion, it is possible to perform the hue conversion and the lightness adjustment processing at high speed.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention.

FIG. 2 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a relationship between hue and maximum brightness.

FIG. 4 is a diagram showing a method of creating a brightness adjustment table of the present invention.

FIG. 5 is a diagram showing an example of a brightness adjustment table of the present invention.

FIG. 6 is a diagram showing a flowchart of the operation of the hue / luminance conversion unit of the present invention.

FIG. 7 is a diagram showing an embodiment of a hue conversion unit in the image processing apparatus of the present invention.

FIG. 8 is a diagram showing a conventional image processing apparatus.

FIG. 9 is an explanatory diagram of hue conversion of a conventional image processing apparatus.

[Explanation of symbols]

 1: Image processing device 2: Image data input unit 5: Conversion instruction unit 10: Hue conversion unit 11: Lightness conversion unit 12: Lightness adjustment table

Front page continuation (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H04N 5/57 9/64 A G06F 15/68 310 A H04N 1/40 D

Claims (4)

[Claims] 1. An image data input section (2) and a hue conversion section (10)
And an image data output unit (4), and an image processing device capable of performing a hue conversion. In order to adjust the lightness of the hue-converted image data to an appropriate lightness, the lightness before the adjustment and the lightness after the adjustment are adjusted. And the brightness adjustment table (12)
And a brightness conversion unit (11) for converting the brightness of the image data with reference to the brightness adjustment table (12), and adjusting the hue of the hue-converted image data to an appropriate brightness, and outputting the adjusted hue. Image processing device. 2. The brightness adjustment table according to claim 1.
(12) is an image processing apparatus characterized in that the relationship between the brightness before adjustment and the brightness after adjustment corresponds non-linearly. 3. The image processing apparatus according to claim 1, wherein the changed lightness value is set to a maximum lightness value or a minimum lightness value. 4. The hue conversion table according to claim 1, further comprising: a hue conversion table in which a hue before the hue conversion and a hue after the hue conversion are associated with each other, and the hue conversion is performed by referring to the hue conversion table. Image processing device.