JP2001061075A - Image processing method, image processor and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and manually set a correction condition by which an excellent correction result can be obtained through the use of the result of automatic correction. SOLUTION: The image processing method has a step (S201) where image data denoting an input image are received, a step (S202) where a color correction condition of the input image is automatically obtained in response to a color distribution of the input image, a step where when a user instructs manual correction, the user is informed of the color correction condition obtained automatically, a revision step (S204) where the user enters a revision to the color correction condition obtained automatically, and a correction step (S205) where the input image is corrected by using the revised color correction condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method, apparatus and recording medium for setting good color correction conditions.

[0002]

2. Description of the Related Art Conventionally, an image processing method for determining a white point and a black point for an image having a low contrast and adjusting the contrast so that the gray level between them is the maximum gray level difference, and the state of the screen histogram. There is an image processing method for determining a gamma value and performing gamma correction.

There are also image processing methods for contrast correction in which a white point and a black point are manually determined, and gamma correction in which a gamma value is manually determined.

[0004]

According to the conventional method of correcting the contrast of image data, an image having a low contrast is
The contrast may be too high.

Further, when a document having a wide dynamic range of exposure amount such as a negative film and having a non-linear characteristic is read as image data, the distribution of image information in the density range of the film is not uniform depending on the image exposure condition. Will be. Therefore, when a negative film is captured by a scanner, it is difficult to automatically perform appropriate contrast correction automatically.

In such a case, the image is manually corrected. However, in the conventional manual correction, the correction is performed on the image on which the automatic correction has been performed.

Further, since the content of the automatic correction process is not displayed, the correction intensity cannot be adjusted. If the image quality of the automatic correction is not satisfactory, it is necessary to manually adjust the original image, and the operation is very troublesome.

The present invention has been made in view of the above points, and has as its object to enable easy setting of good correction conditions.

In particular, it is an object of the present invention to easily and manually set a correction condition for obtaining a good correction result by using a result of the automatic correction.

[0010]

In order to achieve the above object, an image processing method according to the present invention comprises a step of inputting image data representing an input image, and a step of inputting image data according to a color distribution of the input image. A step of automatically finding color correction conditions;
When the user instructs to perform manual correction, a step of notifying the user of the automatically determined color correction condition, and inputting and changing the user's change to the automatically determined color correction condition And a correcting step of correcting the input image using the changed color correction condition.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of image processing utilizing the present invention will be described with reference to a flowchart.

FIG. 1 is a diagram of an operation screen for manual image correction, and FIG. 2 is a flowchart of image processing.

In s201, a multivalued image to be subjected to image correction is stored in a memory. The multi-valued image is a color image having a luminance gradation of each RGB of 8 bits read by an image input device such as a scanner.

In s202, the image correction parameters of the multi-valued image input in s201 are automatically determined, and the display original image obtained by reducing the multi-valued image input in s201 is corrected and displayed as a corrected simulated image. The automatic image correction performed in s202 is automatically performed on an input image without a user's instruction. In the present embodiment, it is forcibly performed.

The image correction in this embodiment is performed using an LUT (Look Up Table), and the lo point (black point) and the hi point (white point) obtained from the luminance histogram of each of the RGB color components of the multi-valued image. ), And gamma correction that performs correction according to the gamma value gamma by the following equation (1) output = ((input / 255) ^ gamma) * 255 (1).

The lo point for contrast correction is black (numerical value
0) to 1% of all pixels, and the hi point is a luminance value from white (numerical value 255) to 1% of all pixels (FIG. 3).
reference). The correction parameter hi and lo values are R_
lo, R_hi, G_lo, G_hi, B_lo, B_hi.

A correction parameter gamma used in gamma correction
Is obtained by Expression (3) such that the average value average_Y over the entire screen of the luminance signal Y calculated from Expression (2) from the RGB of each pixel becomes a predetermined value Target_Y. Correction parameter gamma
Is a common value for RGB.

[0018] Y = 0.299 * R + 0.587 * G + 0.114 * B (2) gamma = log (Target_Y / 255) / log (average_Y / 255) (3)

In s203, the image correction parameters determined in s202 are manually changed or the user selects based on the display image corrected by the image correction parameters determined in s202. If the correction parameters are to be manually changed, the process proceeds to s204. If image processing is to be performed using the current correction parameters, the process proceeds to s205.
The processing moves to.

In s204, the user changes the correction parameters calculated in s202 through the operation screen for manual image correction shown in FIG.

Each part of FIG. 1 will be described. The “original image” displays a reduced version of the multivalued image input in s201 as an original image for display. The “corrected image” performs a correction process based on the correction parameters on the display original image and displays it as a corrected simulation image.

"Black & White Point" is a slide bar for changing the correction parameters R_lo, R_hi, G_lo, G_hi, B_lo, B_hi. When the operation screen is started, the slide bar is displayed in the state of the correction parameters calculated in s202.

"Gamma" is a slide bar for changing the correction parameter gamma, which is also displayed in the state of the correction parameter calculated in s202 when the operation screen is started.

As described above, in the present embodiment, the correction parameters determined by the automatic correction are displayed to the user, and the user can change the correction parameters and perform the manual correction of the image.

"Apply" is a button function for applying the correction parameters set in the slide bar to the correction simulated image, "Reset" is a button function for returning the operation screen to startup, and "OK" is the current correction. “Cancel” is a button function for discarding the current correction parameters and returning to the state of the correction parameters calculated in s202, and terminating the operation screen.

In s205, an image correction process is performed on the multi-valued image input in s201 based on the correction parameters determined in s202 or s204. As an example of an LUT for image correction, a table for contrast correction based on the correction parameters hi and lo is shown in FIG. 4, and the table of FIG.
FIG. 5 shows a gamma correction table to which a gamma correction effect based on the gamma correction is applied.

In the present embodiment, instead of performing manual correction on an image on which automatic correction has been performed, correction parameters determined by automatic correction are changed, and an original image for display is changed using the changed parameters. , It is possible to obtain a good image without deterioration in gradation.

In the case of performing the manual correction, since the intensity of the correction amount can be adjusted based on the correction parameter of the automatic correction, the adjustment of the correction parameter can be easily performed.

In this embodiment, RG is used as a multivalued image.
B Each is 8 bits, but is not limited to 8 bits.
It is determined by the specifications of the system incorporating the present invention. For example, a multi-valued image from a scanner is RGB 12bi
If input at t, the same effect as in the present embodiment can be obtained by setting the lower limit of the histogram distribution width in 12 bits.

[0030]

According to the present invention, good correction conditions can be easily set.

In particular, it is possible to easily and manually set a correction condition by which a good correction result can be obtained by using the result of the automatic correction.

[Brief description of the drawings]

FIG. 1 is an operation screen for manual image correction.

FIG. 2 is a flowchart illustrating a flow of an image processing method.

FIG. 3 is an example of a histogram of an input image and an example of a lower limit and an upper limit.

FIG. 4 is an example of a contrast correction table.

FIG. 5 is an example of a gamma correction table.

Claims (6)

[Claims] 1. A step of inputting image data representing an input image; a step of automatically obtaining a color correction condition for the input image according to a color distribution of the input image; If so, a step of notifying the user of the automatically determined color correction condition, a step of inputting a change to the automatically determined color correction condition of the user, and the changed color correction condition Correcting the input image by using the image processing method. 2. The color correction condition is a contrast correction condition, and based on a black point and a white point of the input image obtained based on a color distribution of the input image, the gradation width between the black point and the white point is 2. The image processing method according to claim 1, wherein the contrast of the image is adjusted so as to have a substantially maximum gradation width of the image. 3. The color correction condition is a gamma correction condition determined from a luminance component frequency distribution of the input image, and is determined so that an average value of the luminance component frequency distribution becomes a predetermined value. The image processing method according to claim 1. 4. The image processing method according to claim 1, wherein the correction using the automatically obtained color correction condition is forcibly performed on the input image. 5. A means for inputting image data indicating an input image; a means for automatically obtaining a color correction condition for the input image according to a color distribution of the input image; and an instruction to perform manual correction by a user. If so, means for notifying the user of the automatically determined color correction condition, means for inputting a change to the automatically determined color correction condition of the user, and the changed color correction condition Means for correcting the input image by using the image processing apparatus. 6. A recording medium in which a program is recorded in a computer-readable manner, wherein inputting image data indicating an input image, and a color correction condition for the input image according to a color distribution of the input image Automatically determining the color correction conditions, and when the user instructs to perform manual correction, informing the user of the automatically determined color correction conditions; and A recording medium recording a program having a change step of inputting a change to a correction condition and a correction step of correcting the input image using the changed color correction condition.