JP2648206B2 - Method of setting output value correction table in image input / output device - Google Patents

Description

The present invention relates to a method for setting an output value correction table in an image input / output device, and more particularly to an image input / output device using a halftone image output as an image forming means. For setting an output value correction table.

(Prior Art) Recently, a color original image is line-scanned, color-separated and input to a specified magnification, and the color-separated signal is subjected to appropriate color correction, sharp angle enhancement, gradation conversion, and the like, and then shaded to obtain C ( A plane scanning type image input / output apparatus has been proposed in which cyan (C), M (magenta), Y (yellow) and black color separations are created by plane scanning.

FIG. 5 is a schematic block diagram of the image input / output device.

In the figure, an input unit 1 linearly scans a color original image, performs color separation input at a specified magnification, and a processing unit 2 subjects the input color separation signal to appropriate color correction, sharpness enhancement, gradation conversion, and other processing. Finally, the output unit 3 shades C, M, Y, and black color separations by plane scanning.

At this time, the output unit 3 determines the area ratio of the halftone dot based on the numerical value input from the processing unit 2, but the input numerical value and the halftone dot area ratio output based on the input numerical value are directly used. Is not a linear relationship. Therefore, an output value correction table is provided at the last stage of the processing unit 2 so that a linear halftone dot area ratio can be obtained for the input numerical value, and the numerical value input to the output unit 3 is corrected.

FIG. 6 is a diagram showing a procedure of a conventional output value correction table setting method.

Conventionally, first, the processing unit 2 generates a test signal to the output unit 3 according to a command from the control unit 4 (step S1). That is, the numerical value V (for example, 0 to 255 when the signal width is 8 bits) within the range of the input signal to the output unit 3 is sent to the output unit 3 with a predetermined value. Next, the output unit 3 shades and outputs the film according to the value of the test signal sent from the processing unit 2 and outputs a halftone step wedge (step S2). At this time, the output of the halftone dot step wedge is the halftone angle (for example, 0) corresponding to the four plates of C, M, Y and black plate.
°, 15 °, 45 °, 75 °), for example, in the case of 21 steps of each plate, 84 halftone step wedges are output.

Next, the operator measures all individual dot area ratios from the output film output from the output unit 3 (Step S).
3 '), and input it to the control unit 4 (step S4').

Then, an output value correction table is created from the relationship between the value of the test signal sent to the output unit 3 and the measured halftone dot area ratio corresponding thereto (step S5). At this time, if interpolation is performed such that a smooth curve is obtained for a set of the value of the test signal and the value of the dot area ratio (for example, spline interpolation or quasi-Hermitian interpolation), the result is shown in FIG. It becomes such a relationship.

(Problems to be Solved by the Invention) As described above, in the conventional method, the output unit 3
The operator actually measured the halftone dot area ratio from the halftone step wedge obtained in step (1), and input the obtained halftone dot area ratio. The output value correction table is
Since the halftone angle, halftone shape, and line must be obtained for each halftone to be used, the amount of work of measuring the halftone dot area ratio and inputting data will increase as the number of usage conditions increases. To increase. Therefore, there is a problem that it takes a lot of time and effort to set an output value correction table in the related art.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for setting an output value correction table in an image input / output device capable of shortening a work time and simplifying a work process. Is to do.

The present invention relates to a method of setting an output value correction table in an image input / output device, and an object of the present invention is to input an image by scanning the image. Image processing means for processing pixel information input from the image input means by various types of image processing, and output means for performing shaded output based on output values from the image processing means. An image input / output device, wherein the image processing unit is configured to convert pixel information into a dot area ratio, and to obtain a dot ratio in a linear relationship with an output value of the output unit. An output value correction table for correcting an output value of the image processing means, wherein the output value correction table is based on a halftone dot step based on a test signal from a control unit provided to the output means. And outputs the halftone dot step wedge to the image input means, calculates and calculates the halftone dot area ratio from the read pixel information, and calculates the test signal value and the test signal value for the calculated halftone dot area ratio. Is obtained by performing an interpolation process on the relationship.

(Operation) According to the present invention, the dot step wedge output based on the test signal is read by the input means, and the dot area ratio of the dot step wedge is automatically calculated from the read pixel information. Since the output value correction table is obtained from the relationship between the calculated dot area ratio and the test signal value,
Time and effort in the setting operation are reduced.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a procedure of an output value correction table setting method in the image input / output device of the present invention. FIG. 2 is a diagram showing an output film. FIG. 3 is a diagram showing halftone dots cut out to m × n pixels. FIG. 4 is a diagram showing an output value correction table. FIG. 5 is a schematic block diagram of the image input / output device.

 The procedure of the embodiment will be described with reference to FIGS.

First, the processing unit 2 generates a test signal to the output unit 3 according to a command from the control unit 4 (step S1). The details are the same as before. Next, the output unit 3 includes the processing unit 2
And outputs a halftone step wedge in accordance with the value of the test signal sent from
2). In this case, as in the conventional case, 84 halftone step wedges are output in the case of 4 steps of 21 steps.

Next, the output film output from the output unit 3 is set in the input unit 1, the halftone step wedge is read as image information (step S3), and stored in the image memory provided in the control unit 4.

Next, the control unit 4 includes a microcomputer, and individually calculates a dot area ratio from the image information of the dot obtained in step S3 (step S4). The calculation method is
For example, it obtains the dot area percent of the value V _i of the test signal corresponding with the information of the m × n pixels as shown in FIG. 3 for the i-th dot step wedge with S _i Tosureba following formula I just need.

S _i = number of pixels of black (1) / m × n The extraction of m × n pixels is performed by designating sample points on the CRT provided in the input unit 1 or automatically if the output format is determined. And cut out. Further, black pixels are identified by setting a certain density threshold and identifying pixels above the threshold as black.

One condition (screen angle, dot shape and number line) the dot percent S _i of the halftone step wedge for the automatically determined from the relationship between the value V _i of the test signal of each stage, those discrete An output value correction table as shown in FIG. 4 is created by interpolating typical data (step S5).

As described above, in this embodiment, the input unit 1 reads the dot step wedge of the output film as image information and automatically calculates the dot area ratio.

As described above, according to the output value correction table setting method in the image input / output apparatus of the present invention, the halftone dot wedge output based on the test signal is read by the input means, and the read pixel information is read. The output value correction table is obtained by automatically calculating the halftone dot area ratio of the halftone dot step wedge, so that the working time can be reduced and the working process can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing a procedure of an output value correction table setting method in the image input / output device of the present invention, FIG. 2 is a diagram showing an output film, and FIG. 3 is a diagram showing halftone dots cut out to m × n pixels. 4 is a diagram showing an output value correction table, FIG. 5 is a schematic block diagram of an image input / output device, FIG. 6 is a diagram showing a procedure of a conventional output value correction table setting method, and FIG. FIG. 4 is a diagram showing the relationship between the output value of the dot pattern and the dot area ratio. 1 ... input unit, 2 ... processing unit, 3 ... output unit, 4 ... control unit.

Claims (1)

(57) [Claims] An image input means for inputting an image by scanning an image, an image processing means for processing pixel information input from the image input means by various types of image processing,
An output unit that performs a shaded output based on an output value from the image processing unit; andan image input / output device including: a processing unit that converts pixel information into a dot area ratio; An output value correction table for correcting the output value of the image processing means so that a dot area ratio having a linear relationship with the output value of the output means is obtained. Outputs a halftone dot wedge based on a test signal from the control unit given to the control unit, causes the image input unit to read the halftone step wedge, and calculates and calculates the halftone dot area ratio from the read pixel information. An output value correction table setting method in the image input / output apparatus, wherein the relation is calculated by performing an interpolation process on a relationship between the calculated dot area ratio and the test signal value.