JPH04238464A - Gradation correction curve input method - Google Patents

Abstract

PURPOSE:To supply a method for easily inputting a highly precise gradation correction curve in a short time without depending on manual work in the input method of the gradation correction curve of a picture signal. CONSTITUTION:A picture read part 3 reading the gradation correction curve plotted on a graph paper and the like and a data processing part 2 extracting coordinate information on multiple points on the gradation correction curve from input picture information and generating and storing data on the gradation correction curve are provided. The highly precise gradation correction curve in which the reproduction of the correction picture signal of a curve part is satisfactory can be inputted by increasing the number of extracting points.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inputting a gradation correction curve for an image signal.

0002

2. Description of the Related Art In image reading devices, facsimile machines, and other image processing devices, it is generally necessary to perform gradation correction processing on image signals.

Conventionally, there are roughly two types of methods for inputting a gradation correction curve for this gradation correction process.

The first method will be explained with reference to FIGS. 2 and 3. FIG. 2 shows an apparatus configuration for inputting a gradation correction curve and performing gradation correction, and FIG. 3 shows an example of graph paper on which a gradation correction curve is drawn.

In this input method, the user draws a desired gradation correction curve on a graph of density (horizontal axis) and halftone dot percentage (vertical axis) as shown in FIG.
Using the dot percentage as the Y coordinate, the XY coordinates of N points on the curve are read, the information on the XY coordinates is input from the keyboard 10, and stored in the key information input buffer 11. From these N pieces of input information, the arithmetic unit 12 performs arithmetic processing using the polygonal line approximation method to create gradation correction curve data that matches the bit configuration and device functions of the multivalued image that is the target of gradation correction. , and are stored in the correction curve storage section 13 together with the curve number.

When actually performing gradation correction of an image signal, the data of the gradation correction curve of the curve number specified by the user is loaded into the correction curve storage section 1 by the curve loading section 14.
3 and loaded into the conversion unit 15 (consisting of RAM). The converting section 15 corrects the image signal input from the image reading section (not shown) according to the loaded correction curve data and outputs an image signal.

Note that a key information input buffer 11, a calculation section 12, a correction curve storage section 13, and a curve load section 14
is actually realized by a microcomputer.

The second conventional gradation correction curve input method is as follows:
The converting section (corresponding to the converting section 15 in FIG. 2) for correcting the gradation of the image signal is configured in a ROM, and the data of the gradation correction curve is written directly into the ROM using dedicated software on an external personal computer, and this ROM is then read. This method is to set it in the converter.

[0009]

[Problems to be Solved by the Invention] However, with the above-mentioned input method, it is difficult to prevent deterioration in the reproducibility of the corrected image signal in the curved part of the gradation correction curve, and it is difficult to read the graph or use the keyboard when inputting. Since the operations are performed manually, the input work is troublesome and time consuming, and the second input method also requires a separate personal computer.

[0010] The above-mentioned reproducibility will be explained. In order to perform high-precision tone correction with good reproducibility on the curved part of the tone correction curve, assuming that the bit configuration of the multivalued image to be handled is M bits, 2 M bits on the desired tone correction curve must be All you have to do is input the information for the multiplied number of points. However, it is impossible to do this manually due to work time and other considerations, so in reality, information on N points, which is much smaller than that, is input.
Because the missing point information is interpolated using the polygonal line approximation method,
The accuracy of the curved portion of the curve was poor, causing poor reproducibility.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for inputting a highly accurate gradation correction curve easily and in a short time without relying on manual labor. do.

0012

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention prepares graph paper or the like on which a desired gradation correction curve is drawn, and reads the image information on this paper by an image reading means to create data. The data processing means extracts coordinate information of multiple points on the gradation correction curve from the input image information, and creates and stores data of the gradation correction curve from this coordinate information. It is prepared.

[0013]

[Operation] As described above, in the present invention, since the coordinate information of the points on the gradation correction curve is extracted by the data processing means from the image information of the paper, the number of extraction points can be easily increased. A high-precision tone correction curve that does not require interpolation using an approximation method or has good reproducibility of corrected image signals in curved sections by extracting coordinate information of a large number of points where approximation errors can be ignored. can be entered. Furthermore, since the input method does not depend on human hands, input time can be shortened.

[0014]

[Embodiment] FIG. 1 is a schematic configuration diagram of an image processing apparatus according to an embodiment of the present invention, in which 1 is a conversion unit for performing gradation correction, and 2 is a data processing unit for inputting a gradation correction curve. ,3
is an image reading section. In this embodiment, one image reading section 3 reads the image to be processed by the converting section 1 and reads the image for inputting the gradation correction curve, but each image reading is performed by separate image readings. It is also possible to adopt a configuration in which this is performed by means.

The data processing section 2 consists of a sampling input buffer 4, a point extraction section 5, a calculation section 6, a correction curve storage section 7, and a curve loading section 8, which are actually realized by a microcomputer. Good too.

The gradation correction curve input using such an apparatus configuration will be explained below. When inputting a gradation correction curve, the user draws the gradation correction curve that he/she wants to input as shown in FIG. Instructs to start reading. The image of this graph paper is read by the image reading section 3, and the image signal is sent to the data processing section 2.
Enter. The image signal at this time may be a black-and-white binary signal or a multi-value signal.

In the data processing section 2, a sampling input buffer 4 samples the image signal and stores image information of the graph paper. The point extraction unit 5 scans this image information, divides the image into 2 to the M power in each of the X and Y directions, distinguishes between ground and lines (gradation correction curve), and divides the image into 2 to the M power on the gradation correction curve. Extract the coordinates of points. However, here, converter 1
It is assumed that the image signal to be subjected to the gradation correction is of M-bit configuration. Therefore, at this stage, all the coordinate information of the necessary points on the gradation correction curve has been obtained, and there is no need to interpolate points using polygonal line approximation as in the conventional method. However, since there is an anti-logarithmic relationship between reflectance and density, the extraction point coordinate information is subjected to logarithmic correction processing in the calculation unit 6.
Furthermore, by performing processing to create a necessary data format, final gradation correction curve data is created and stored in the correction curve storage section 7. At this time, a curve number is also added.

The gradation correction curve input in this way is based on the coordinate information of multiple points extracted from the image information, and is free from errors in line approximation and errors that occur when reading the graph manually. It has sufficient accuracy even on curved parts.

Next, the case where gradation correction is performed will be explained. The user sets the document to be processed in the image reading section 3, specifies a desired curve number using a switch (not shown), etc., and instructs to start reading.

The curve loading unit 8 of the data processing unit 2 reads data of the gradation correction curve of the designated curve number from the correction curve storage unit 7 and loads it into the conversion unit 1.

When this loading is completed, the image reading section 3 starts reading the image of the original, and inputs the image signal (M-bit multi-value signal) to the converting section 1. The conversion unit 1 performs gradation correction on an input image signal according to a gradation correction curve, and outputs a corrected image signal. This correction is performed using a highly accurate gradation correction curve, and a corrected image signal with good reproducibility can be obtained even in the curved portion.

Note that the number of points extracted by the point extraction section 5 does not necessarily have to be 2 to the M power, and it is possible to reduce the number of points. In this case, it is necessary to interpolate the missing points using a polygonal line approximation method or the like, but if the number of extraction points is selected so that the approximation error does not become a problem, highly accurate gradation correction is possible.

[0023]

As is clear from the above description, the present invention extracts the coordinate information of points on the gradation correction curve from the image information of the paper using the data processing means, so that the number of extraction points can be sufficiently increased. High-precision tone correction is possible by inputting a high-precision tone correction curve with good reproducibility of the corrected image signal even in curved areas, and the tone correction curve can be input in a short time without relying on manual operations. This has the effect of making it possible.

[Brief explanation of the drawing]

FIG. 1 is an apparatus configuration diagram for explaining a tone correction curve input method according to an embodiment of the present invention.

[Fig. 2] Device configuration diagram for explaining the conventional input method

[
Figure 3: Diagram showing an example of graph paper on which a gradation correction curve is drawn

[Explanation of symbols]

1 Conversion section 2 Data processing section 3 Image reading section 4 Sampling input buffer 5 Point extraction part 6 Arithmetic section 7 Correction curve storage section 8 Curve road section

Claims (1)

[Claims] 1. Image information of a sheet of paper on which a gradation correction curve is drawn is read by an image reading means and inputted to data processing means, and the data processing means obtains coordinate information of multiple points on the gradation correction curve from the input image information. A gradation correction curve input method characterized by extracting , and creating and storing gradation correction curve data from this coordinate information.