JPH088697B2 - How to convert image data to black and white - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for converting image data into black and white, and more particularly to providing a printer for printing image data with a black and white conversion processing mechanism. .

[Prior Art] FIG. 4 is a flow chart for explaining a conventional monochrome conversion method of image data. In FIG. 4, all the gradation numbers of three components, for example, Y-MC components are OOH.
In the case of, the corresponding image is regarded as white, and when the maximum value FFH, the corresponding image is regarded as black.

First, in step (S1), Y is set to arbitrary image data.
-Decompose into M-C component and express the gradation number with an appropriate value from OOH to FFH. In the next step (S2), it is decided whether or not the black-and-white conversion is to be performed, and if not, the processing is terminated, and the decomposed Y-MC component is printed with the same gradation number. On the other hand, if black-and-white conversion is to be performed, in the subsequent step (S3), it is determined whether or not all the gradation numbers of the decomposed Y-MC components are OOH.
When the result of the determination in this step (S3) is YES, that is, when all the gradation numbers of the YMC components are OOH, the corresponding image is regarded as white, and the following step ( In S4), black-and-white conversion is performed, all the gradation numbers of the Y-MC components are set to FFH, and the process ends. Therefore, OOH
The white level image of is converted into the FFH black level image, and printing is performed. On the other hand, when the result of the judgment in the previous step (S3) is NO, that is, the decomposed Y-M
If even one of the -C components is not OOH, it is determined in step (S5) whether all the Y-MC components are FFH. Will be done. When the result of the determination in this step (S5) is YES, that is, when all the gradation numbers of the decomposed Y-MC components are FFH, the corresponding image is regarded as black,
In the next step (S6), black and white conversion is performed and Y
All the gradation numbers of -MC components are set to OOH, and the processing is finished. Therefore, the FFH black level image is converted into the OOH white level image and printing is performed.

If any one of the decomposed YMC components does not have OOH or FFH, the black and white conversion is not performed for such an image, and the processing is terminated and the decomposition is performed. Printing is performed with the number of gradations of the Y, M, and C components thus changed.

Thus, according to the conventional example described above, an image in which all the gradation numbers of the Y-MC components are OOH as shown in FIG. The image is converted into an image whose number is FFH, and conversely, an image in which all the numbers of gradations of Y-MC components are FFH as shown in FIG. 7 has all the gradations as shown in FIG. The image is converted into an image whose number is OOH, but other images, for example, the image in which the number of gradations of Y-M-C components is neither OOH nor FFH, as shown in Fig. 2, is not converted into black and white. It will be.

[Problems to be Solved by the Invention] In the conventional black-and-white conversion method, since the image to be black-and-white converted is limited to perfect white or black as described above, half-tone images are not black-and-white converted. Color continuity cannot be maintained. Also, when converting the image signal input from the video I / F circuit to black and white, the video signal is unstable, and even if it is a white image, it may not reach the perfect white level (OOH). There is a problem in that an image that has to be converted into black and white is not converted.

The present invention has been made in order to solve such a problem, and an object thereof is to obtain a black-and-white conversion method that can maintain color continuity and follow instability of a video signal.

[Means for Solving the Problems] In the black-and-white conversion method of image data according to the present invention, arbitrary image data is decomposed into Y-M-C components or R-G-B components to obtain a white level and a black level. The steps include steps and a step of performing black-and-white conversion from the white level and the black level thus obtained.

[Operation] In the present invention, the white level and the black level at the time of black-and-white conversion are not fixed, and for example, decomposed Y-MC
It is determined by the number of gradations of the component.

[Embodiment] The present invention will be described below with reference to the flowchart of FIG. 1 showing an embodiment thereof. FIG. 1 exemplifies a case where the minimum value and the maximum value of the number of gradations of the Y-MC component are OOH and FFH, respectively.

First, similarly to the conventional example, in step (S1), arbitrary image data is decomposed into YMC components, the gradation number is represented by an appropriate numerical value from OOH to FFH, and the next step (S2) If the black-and-white conversion is not performed in step 1, the processing is terminated, and the decomposed Y-MC component is printed with the same number of gradations.

On the contrary, in the case of performing black-and-white conversion, in the subsequent step (S7), the minimum number of gradations among the decomposed Y-MC components, that is, the number of gradations of the tertiary color component. And set this as the black level. Further, in the next step (S8), the maximum number of gradations among the Y-MC components, that is, the number of gradations of the primary color component is obtained, and the value is calculated from the maximum value FFH of the number of gradations. Subtract the white level. Based on the black level and the white level obtained as described above, in the subsequent step (S9), black-and-white conversion is performed, and the process ends.

That is, in the black-and-white conversion, the black level obtained in the previous step (S7) is subtracted from the number of gradations of each of the decomposed Y-MC components, and the white level obtained in the previous step (S8) Add the levels to obtain each gradation number. Therefore, the black level and the white level are exchanged, and the printing is performed.

For example, as shown in Fig. 2, when the gradation number of the decomposed Y-MC component is Y: 8FH, M: 6FH, C: 3FH, the black level is the minimum gradation number = 3FH. , The white level is FFH-8FH (maximum number of gradations) = 70H. Therefore, Y-M after black and white conversion
-The gradation number of C component is Y: 8FH-3FH + 70 as shown in Fig. 3.
H = COH, M: 6FH-3FH + 70H = AOH, C: 3FH-3FH + 70H = 70H.

In the above-mentioned embodiment, the case where the maximum value of the number of gradations of the Y-MC component is set to FFH has been described.
This is merely an example and the present invention is not limited to this value.

In addition, arbitrary image data was decomposed into Y-MC components, and the white level and black level used in black-and-white conversion were obtained from the decomposed Y-MC components. The white level and the black level may be obtained by decomposing into components and using the same method. However, in this case, the minimum gradation number of the decomposed R-G-B components, that is, the gradation number of the tertiary color component is set as the white level, and the maximum gradation of the R-G-B components is set. The value obtained by subtracting the number from the maximum value of the number of gradations is the black level.

[Effects of the Invention] As described in detail above, according to the present invention, a step of decomposing image data into three components of Y-M-C components or R-G-B components and a white level from the three components thus decomposed. And the step of obtaining the black level and the step of performing the black and white conversion from the white level and the black level obtained in this way, the white level and the black level when performing the black and white conversion are not fixed, but a perfect white level. And, the black and white conversion is performed without being limited to the image of the complete black level. Therefore, for example, a halftone image of reddish black is also converted to reddish white, and color continuity is maintained. Further, there is an effect that it is possible to follow the instability of the video signal.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining a monochrome conversion operation according to an embodiment of the present invention, FIGS. 2 and 3 are explanatory views of the present invention, and FIG. 4 is a conventional monochrome conversion method. Flow charts and FIGS. 5 to 8 are explanatory views of the conventional method. In each figure, the same reference numerals indicate the same or corresponding parts.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 1/387 1/46

Claims (2)

[Claims] 1. A step of decomposing image data into three components Y-M-C, and a minimum gradation number of the decomposed three components is set to a black level, and the predetermined gradation number A step of subtracting the maximum number of gradations of the components to obtain a white level, and a step of subtracting the black level from the number of gradations of each of the three components and adding the white level to perform black and white conversion. A method for black and white conversion of image data. 2. A step of decomposing image data into three components of R, G, and B, and a minimum gradation number of the decomposed three components is set to a white level, and the predetermined gradation number is used to obtain the three gradation values. A step of subtracting the maximum number of gradations of the components to obtain a black level, and a step of subtracting the black level from the number of gradations of each of the three components and adding the white level to perform black and white conversion. A method for black and white conversion of image data.