JPH061343B2 - Copy exposure amount determination method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical copying apparatus such as a photographic printing apparatus or a CR.
Used in T printers, copiers, laser printers, etc.
The present invention relates to a method for determining a copy exposure amount when copying a color original image onto a recording medium.

[Conventional technology]

An optical copying apparatus for recording a copy image faithful to a color original image extracts red, green, and blue image characteristic amounts from the color original image and reproduces red, green, and blue images according to these image characteristic amounts. The amount of exposure is controlled. For example, in a color photographic printing apparatus, the red average density, the green average density, and the blue average density of each color negative screen are calculated, and the red exposure amount, the green exposure amount, and the blue exposure amount are calculated according to these average densities. is doing. In addition, it is a photographic printing device equipped with a black and white image area division photometric device, but by dividing the original image into multiple areas and specifying the area where the main image exists, the image feature amount from this area can be specified. There is also known a method of correcting the basic exposure amount extracted and calculated from the screen average density with the main image feature amount (Japanese Patent Publication No. 55-2941).
issue).

Further, there is known a method of automatically extracting a flesh-colored portion in a positive image from a color original image and controlling an exposure amount at each place so that this portion has a predetermined density on the positive image (JP-A-52-156625). No. 54-68632).

[Problems to be solved by the invention]

In the above-mentioned conventional method, since the image feature amount of the background image area is not used, appropriate exposure control cannot be performed depending on the image type. That is, in the conventional method, even if the image type is different, such as a backlit scene (sky or white wall), landscape, indoor (different light source), night view, flash photography, etc.
Although the main subject, for example, the face of a person is printed with the same density, it is desirable to finish the density in consideration of the background. Further, in an original image that is under or over, since the main image has a constant density, the shadow portion and highlight portion of the image become unnatural.

Further, it is well known that the average color density of an average outdoor color image is close to gray. Since this empirical rule holds true for the background image, the color balance becomes better when the basic amount of color is calculated from the background image area.

[Object of the Invention]

INDUSTRIAL APPLICABILITY The present invention is capable of appropriately performing exposure control from an image in which importance is attached to a main image, such as a night view or a flash photography, to an image in which a background image needs to be considered, such as landscape, backlight, or different light source. It is an object of the present invention to provide a copy exposure amount determination method that can be performed.

Another object of the present invention is to provide a method for determining a copying exposure amount that enables copying with good color balance.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention displays a positive image of a color original image on a monitor, and observes this monitor to specify the position of a main image, and by specifying this position, the main image area and the main image area are excluded. A basic image for controlling the density and color from the obtained background image feature amount by determining the background image region that is all or a part of the color original image, and obtaining the image feature amount of each color from each of these image regions. The exposure amount is calculated for each color, and the correction amount for the basic exposure amount is calculated for each color from the main image feature amount.

The main image areas are light pen, touch panel sensor,
When you specify a part of the main image with the cursor,
It can be determined by extracting pixels having the same or similar density or color as the pixels of this portion. At this time, the main image area may be a continuous area on the color original image or a dispersed discontinuous area. Alternatively, the area can be directly specified by indicating the boundary of the main image.

The whole or part of the portion excluding the main image area is the background image area. Many people are the main images, and in this case, in order to remove clothes, hair, shadows, etc., a certain area surrounding the main image area is set as the intermediate image area, and the other area is set as the background image area. Is good. Further, when the main image area is large, it is preferable to set all the areas other than the main image area as the background image area. Further, a certain area existing on the periphery of the screen may be defined as the background image area.

Various image feature amounts are extracted for each color from the main image region and the background image region thus determined. Then, the basic exposure amount is obtained for each color from the background image feature amount, and the correction amount for correcting the basic exposure amount is obtained for each color from the main image region. The exposure amount for each color is calculated by adding the obtained basic exposure amount and correction amount for each color.

Hereinafter, embodiments in which the present invention is applied to a photo printing apparatus will be described in detail with reference to the drawings.

〔Example〕

FIG. 1 shows an example of a photographic printing apparatus embodying the present invention. The white light emitted from the white light source 10 passes through the diffusion tube 11 and the negative carrier 12, and reaches the color original image, for example, the color negative film 13 set at the printing position,
This is illuminated from below. The diffusion cylinder 11 is composed of a square cylinder 14 whose inner surface is a mirror surface, and two diffusion plates 15 fixed to both ends thereof. This diffusion cylinder 11
And a white light source 10, a cyan filter 16 for adjusting the red component of the illumination light, a magenta filter 17 for adjusting the green component, and a yellow filter 18 for adjusting the blue component. It is arranged. The filter adjustment unit 19 adjusts the insertion amount of each color filter 16 to 18 into the optical path 20 according to the calculation result of the exposure amount calculation formula described later. For example, if the insertion amount of the cyan filter 16 is increased, the red component of the illumination light decreases,
Red exposure is reduced. The color negative film 13
Is pressed from above by a mask 21 which is operated by a solenoid (not shown) during photo printing.

A lens 24 is arranged above the color negative film 13, and a color negative image is formed on the color photographic paper 26 while the shutter 25 is open. The shutter drive unit 27 opens the shutter 25 for a fixed time to give a standard exposure time. When the printing of one frame is completed, the exposed portion of the color photographic paper 26 is taken up by the take-up reel 28, and at the same time, the unexposed portion is pulled out from the supply reel 29.

A half mirror 32 is tilted in the optical path 20, and the light reflected by the half mirror 32 is reflected by a lens 33.
After passing through, it reaches the half mirror 34. The light transmitted through the half mirror 34 is incident on the sensor unit 35, and the light reflected downward is incident on the color TV camera 36. The sensor unit 35 includes a lens 37, a color filter 38, and an image sensor 39, and the three-color signals (red, green, blue) of each pixel of the color negative image are independently or mixed for each color. To output. In this embodiment, one image sensor is used to extract the three-color signals of 25 × 25 pixels (measurement points) in order to reduce the cost, but instead of this, red, green, and blue are used. You may use the three image sensors of.

The three-color signal extracted from the image sensor 39 is converted into a digital signal by the A / D converter 40, and then converted into a density signal by the logarithmic converter 41, and then converted into a micro signal via the I / O port 42. It is taken into the computer 43. As is well known, the microcomputer 43 includes an I / O port 42, a CPU 44, a RAM 45, and an RO.
M46 and M46, which calculates the amount of exposure and controls each part, which will be described later. The RAM 45 separates the captured color density signal for each color, and the frame memory units 45a to 4a.
5c, respectively. The keyboard 47 includes keys for controlling each unit. The half mirror 32 is preferably retracted from the optical path 20 at the time of printing a photograph in order to effectively utilize the light amount of the white light source 10.

The color TV camera 36 captures a color negative image and outputs a video signal. This video signal is converted into a positive image video signal by the negative / positive converter 48, and then,
It is sent to the controller 49. This controller 49
Displays a positive image 51 on the display surface of the color monitor 50 and sends the position information created from the synchronization signal to the position detector 52. The positive image 51 is observed, and if it is recognized as the main image, a part of the image is designated by the position designating means, for example, the light pen 53. The light pen 53 photoelectrically converts the point designated on the color monitor 50 and sends it to the position detector 52. The position detector 52 sends the coordinate position on the color monitor 50 to the microcomputer 43 when a signal from the light pen 53 is generated.

In addition to the light pen 53, a touch panel sensor, a joystick, a digitizer, a trackball, an XY cursor, or the like can be used as the position designating means.
In addition to this, a spot illumination section or a liquid crystal panel is arranged under the negative carrier 12, and the image sensor unit 3 is provided with a state where a part of a main image is illuminated or dimmed and a state where it is not illuminated.
It is also possible to detect the coordinate position of the portion where the illumination state is different by measuring each at 5 and comparing the two photometric values for each pixel in the microcomputer 43. Further, the base density may be checked, the density may be measured in a state where a part of the main image is spot-illuminated, and pixels having a density lower than the base density may be detected. Alternatively, the main image area may be directly specified by tracing the boundary of the main image.

FIG. 2 shows an image sensor. The image sensor 39 includes a blue photoelectric conversion unit 55 having a blue filter on the light receiving surface, a green photoelectric conversion unit 56 having a green filter on the light receiving surface, and a red photoelectric conversion unit 57 having a red filter on the light receiving surface. And are alternately arranged in a matrix at a constant pitch. Of this matrix, a pixel measuring unit 58 for measuring one pixel of a color negative image is composed of 3 × 3 photoelectric conversion units 56 to 57. The pixel measuring unit 58 is surrounded by a dotted line.

When the signals of the photoelectric conversion units are read out, signals of the same color are added and read out in the same pixel, or read out in a mixed form of the color signals and the microcomputer 4
It may be stored in the RAM 45 after being temporarily stored in the RAM 3, then added in the pixel. In this embodiment, since the photoelectric conversion units of the same color are appropriately scattered in the pixel measuring unit 58, the occurrence of color registration can be considerably reduced. For the number of pixel measuring units 58, for example, 25 in the vertical direction and 25 in the horizontal direction are sufficient.
Note that, simply, the pixel measurement unit may be configured by three photoelectric conversion units that are arranged in a line horizontally or vertically or three photoelectric conversion units that form a triangle.

FIG. 3 shows the procedure of exposure control, and the operation of the photographic printing apparatus of FIG. 1 will be briefly described with reference to this. The color negative film 13 is transferred by a transfer means (not shown), and the frame to be printed is transferred to the negative carrier 12
Position on top of. Since the filter adjusting unit 19 holds the tip ends of the color filters 16 to 18 at the standard position in the optical path 20, a part of the white light emitted from the white light source 10 is a color filter. After passing through 16 to 18 and being sufficiently diffused by the diffusion cylinder 11, the color negative film 13 is reached. This color negative film 1
The light transmitted through 3 passes through the lens 24, the half mirror 32, and the lens 33, respectively, and enters the half mirror 34. The light transmitted through the half mirror 34 enters the sensor unit 35, and the light reflected by the half mirror 34 enters the color TV camera 36.

The sensor unit 35 scans the color negative image to measure the three color components of each pixel, and outputs the color signal of each pixel. This color signal is A / D converted and logarithmically converted, and then stored in the RAM 45 of the microcomputer 43 in a separated state for each color. In addition, the video signal output from the color TV camera 36 is negative-positive converted, and then the color monitor 5 is transmitted via the controller 49.
0, and a positive image is displayed on the display surface. By observing the color monitor 50, a part of the portion recognized as the main image is designated by the light pen 53. The position instructed by the light pen 53 is detected by the position detector 52, and the position information is input to the microcomputer 43.

The microcomputer 43 sequentially compares the densities or colors of the pixels on the outside with the densities or colors of the designated portion as a reference, and determines whether they are the same or similar. Since the same or similar pixels are pixels forming the main image, data indicating the main image is written in each memory cell 60 of the image area table. In FIG. 4, reference numeral 61 is a light pen 53.
The pixel that is specified by, and the hatched part 62
Is an area determined to be the main image area.

Next, the area of the background image is determined. When the number n of pixels forming the main image area is smaller than α, an intermediate image area 66 is formed around the main image area 65 to form the background image area 67 as shown in FIG. Then, the data indicating that the pixel is a pixel forming the background image is written in the image area table. The reason for providing the intermediate image area in this way is to eliminate the influence of hair and clothes. Here, when α is N, for example, N is N
/ 2 is used.

When the number of pixels N in the main image area is larger than α, the background image area is small and it becomes impossible to obtain sufficient data. In such a case, as shown in FIG. 6, all the remaining areas except the main image area 68 shown by cross hatching are set as the background image area 69.

As described above, after determining the main image area and the background image area, the image feature amount of each image area is calculated for each color. An image feature amount of the obtained background image area, _(i-red, green, represent any one of a blue) Basic exposure Ef i for controlling the color and density is calculated, and the main image area from the image feature amount, it calculates a correction amount Ec _i for the base exposure. This basic exposure amount Ef _i and the correction amount Ec
_The exposure amount E _i is obtained by adding _i and _i . If no main image is specified, the entire image area is assumed to be the background image area,
An image feature amount is calculated from this background image area. In this case, since the correction amount Ec _i is not calculated, the basic exposure E
exposure amount is adjusted only by f _i.

The calculated exposure amount E _i is sent to the filter adjusting unit 19, and the color filters of the corresponding color and the complementary color are extracted stepwise from the standard position or are further inserted toward the center of the optical path 20. This allows the color filters 16-18
The amount of light to be inserted into the optical path 20 is adjusted stepwise, and the three-color light components of the printing light are adjusted. And color filters 16-18
The amount that cannot be corrected by is sent to the shutter drive unit 27,
The exposure time of the shutter 25 is appropriately increased or decreased.

When the print key of the keyboard 47 is operated, the shutter 25 opens for a fixed time, and the color negative image is printed on the color photographic paper 26. After printing, color photographic paper 26
Also, the color negative film 13 is fed by one frame. At the same time, the filter adjusting unit 19 returns the color filters 16 to 18 to the standard position of the optical path 20.

Next, the exposure amount calculation formula will be described. As the image feature amount, for example, red average density, green average density,
The blue average density is used. As the average color density, a value obtained by adding the color density of each pixel for each color and dividing this by the number of pixels, or an intermediate value between the maximum color density and the minimum color density is used.

The red average density of the background image area and R ^s, the green average concentration of G ^s, when the blue average density and B ^s, the basic amount of exposure Ef _i, can be calculated from the following equation.

Ef _i = a _i + b _i (R ^s −R ₀ ^s ) + c _i (G ^s −G ₀ ^s ) + d _i (B ^s −B ₀ ^s ) ... (1) where the symbols a _i and b _i , C _i , d _i are coefficients determined for each color. In addition, R ₀ ^s , G ₀ ^s , and B ₀ ^s are constants, which are the red average density, green average density, and blue average density of the background image area of a standard color negative image.

In addition, a fixed image area (center image area) in the center of the screen
Alternatively, the basic exposure amount may be calculated using the image feature amount (R ^c , G ^c , B ^c ) of this region. In this case, the following equation (2) is used.

Ef _i = ^{_{[a1 i + b1 i (R c}} -R 0 c) + c1 i (G c -G 0 c) + d1 i (B c -B 0 c) ] + ^{_{[a2 i + b2 i (R s}} -R 0 s ^{_{) + c2 i (G s -G}} 0 s) + d2 i ( in B s _-B ^{0 s)]} ... (2) where the symbols _{a1 i, b1 i, c1 i} , d1 i, a
2 _i , b2 _i , c2 _i and d2 _i are coefficients respectively. R ₀ ^c , G ₀ ^c , and B ₀ ^c are constants, which are the red average density, green average density, and blue average density of the central image area of a standard color negative image.

If the red average density of the main image region is R ^p , the green average density is G ^p , and the blue average density is B ^p , the correction amount Ec
_i can be obtained from the following equation.

^{_{Ec i = e i + f i}} (R p -R 0 p) + g i (G p -G 0 p) + h i (B p -B 0 p) ··· (3) _where, e _{i, f i,} g _i and h _i are coefficients respectively. Further, R ₀ ^p , G ₀ ^p , and B ₀ ^p are constants, which are the red average density, green average density, and blue average density of the main image area of a standard color negative image.

Further, the following formula can be used instead of the correction amount calculation formula (3).

_{Ec i = e i '+ f} i' R p + g i 'G p + h i' B p -ΣK ij V ij ·· (4) where the symbols _{e i ', f i',} g i ', h i' Is a coefficient. V _J is the average density of the full screen or partial screen,
Image features such as maximum value and minimum value, and the number of terms is 50
Not more than one. K _j is a coefficient determined for each color.

And a correction amount Ec _i the fundamental exposure amount Ef _i, exposure E
_i is calculated.

E _i = Ef _i + Ec _i (5) Although the above embodiment is a color photographic printing apparatus, the present invention is a color negative inspection machine and other optical copying apparatuses such as color copying machines, laser color printers and CRT color printers. Etc. can also be used. In particular, the present invention can also be used in the case where the background image area corresponds to the background of the original image such as the original image in a color copying machine.

〔The invention's effect〕

In the copy exposure amount determination method of the present invention, the image feature amount is calculated separately from the main image region and the background image region, the basic exposure amount is obtained from the background image feature amount, and the correction amount is obtained from the main image feature amount. Therefore, images that require emphasis on the main image (night view,
It is possible to perform appropriate exposure control depending on the image type, from a strobe etc.) to an image (landscape, backlight, different light sources, etc.) that needs to consider the background image. By using the present invention in a color copying machine or the like, it is possible to easily obtain an appropriate balance between background density or background image density and main image density.

Further, since the basic exposure amount is calculated from the image feature amount of the background image area, it is easy to achieve the gray balance by using the empirical rule that the average density of the subject in the outdoors is close to gray.

Furthermore, when determining the basic exposure amount by the main image feature amount, it is necessary to set an arithmetic expression according to the type of the main image, but the present invention calculates the basic exposure amount by the background image feature amount. Therefore, the same exposure amount calculation formula may be used, and it is not necessary to set conditions or specify the type of main image, and management and operation are easy.

[Brief description of drawings]

FIG. 1 is a schematic view showing a photographic printing apparatus embodying the present invention. FIG. 2 is an explanatory view showing an example of the image sensor. FIG. 3 is a flowchart showing the procedure of exposure control. FIG. 4 is an explanatory diagram showing an image area table. FIGS. 5 and 6 are explanatory views showing examples of the areas of the background image and the main image, respectively. 10 White light source 13 Color negative film 16 Cyan filter 17 Magenta filter 18 Yellow filter 26 Color printing paper 32, 34 Half mirror 35 Sensor unit 36 Color TV camera 50・ ・ Color monitor 51 ・ ・ Positive image 53 ・ ・ Light pen 65,68 ・ ・ Main image area 67,69 ・ ・ Background image area 66 ・ ・ Intermediate image area

Claims (7)

[Claims] 1. A copy exposure amount determination for determining a copy exposure amount of each color when a color original image is copied onto a recording medium according to a photometric value of each color obtained by performing three-color separation photometry on each pixel of the color original image. In the method, a positive image of a color original image is displayed on a monitor, the position of the main image is designated by observing the monitor, and the main image area and all or part of the color original image excluding this is designated by this designation. The background image area is determined, the image feature amount of each color is obtained from each of these image regions, and the basic exposure amount for controlling the density and the color is calculated for each color from the obtained background image feature amount. A method for determining a copy exposure amount, characterized in that a correction amount for a basic exposure amount is calculated for each color from a main image feature amount. 2. The main image area is determined by automatically extracting pixels having the same or similar color or the same or similar color density as the color of a point designated on the monitor. The method for determining a copy exposure amount according to claim 1. 3. When the main image is not designated, or when the number of pixels belonging to the main image area is a certain value or more, the entire screen is set as the background image area. The method for determining a copying exposure amount according to item 1 or 2. 4. The copy exposure amount determination according to claim 1, wherein an intermediate image area is defined between the main image area and the background image area. Method. 5. The main image feature amount and the background image feature amount are
The method for determining a copying exposure amount according to any one of claims 1 to 4, which is an average density. 6. A standard color original image and a color original image to be copied, in which a copying condition is set so that the standard color original image has a predetermined copy density and the background image area density of the standard color original image is stored in a memory. 6. The copying exposure amount determination method according to claim 1, wherein the basic exposure amount is calculated from the density difference of the background image area. 7. The method according to claim 1, wherein the recording medium is color photographic paper.