Image processing apparatus, error diffusion processing method, and program

Abstract

An image processing apparatus includes a dividing portion that divides input multivalue image data into a plurality of bands, an error diffusion process portion that carries out an error diffusion process on each divided band to quantize each pixel, and a controlling portion that controls the dividing portion and error diffusion process portion. The error diffusion process portion, following control by the controlling portion, operates in a first mode to repeat the error diffusion process not accompanying quantization given times on each noted pixel included in a given line of the each band (head line, etc.), and operates in a second mode to carry out the error diffusion process on the each band sequentially from the head line of the each band on the basis of an error value obtained in the first mode to put out quantized data.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example of the configuration of the principle part of an image processing apparatus according to one embodiment of the present invention;

FIG. 2 depicts an example of an error diffusion process table used for an error diffusion process according to the present invention;

FIG. 3 is a circuit diagram of an example of the detailed configuration of an error diffusion process portion according to the present invention;

FIG. 4 is a circuit diagram of an example of the detailed configuration of a diffusion error calculating portion shown in FIG. 3;

FIG. 5 depicts an example of a diffusion error calculation condition;

FIG. 6 is a circuit diagram of an example of the detailed configuration of a latch/adder shown in FIG. 3;

FIG. 7 is an explanatory flowchart of an example of an error diffusion processing method according to the present invention;

FIG. 8 is an explanatory flowchart of another example of the error diffusion processing method according to the present invention;

FIG. 9 depicts an example of tone values of an original image that is before undergoing an error diffusion process in binarization;

FIG. 10 depicts an example of the error diffusion process table used for the error diffusion process;

FIG. 11 depicts a result of calculation of diffusion errors at the first noted pixel in the original image in a case of the use of the error diffusion process table;

FIG. 12 depicts tone values that results after the diffusion errors are scattered in the original image;

FIG. 13 an explanatory view of a trouble occurring at the boundary between bands; and

FIG. 14 is an explanatory flowchart of a conventional error diffusion processing method.

Claims

1. An image processing apparatus comprising: a dividing portion that divides input multivalue image data into a plurality of bands;an error diffusion process portion that carries out an error diffusion process on each divided band to quantize each pixel; anda controlling portion that controls the dividing portion and the error diffusion process portion, whereinthe error diffusion process portion follows control by the controlling portion to calculate an error value on each noted pixel of the each band without quantizing the noted pixel and diffuse the calculated error value to surrounding pixels around the each noted pixel.

2. The image processing apparatus of claim 1, wherein the error diffusion process portion follows control by the controlling portion to operate in a first mode and in a second mode, the error diffusion process portion in the first mode repeating an error diffusion process not accompanying quantization given times on each noted pixel included in a given line of the each band, and the error diffusion process portion in the second mode carrying out an error diffusion process on the each band sequentially from a head line of the each band on the basis of an error value obtained in the first mode to put out quantized data.

3. An image processing apparatus comprising: a dividing portion that divides input multivalue image data into a plurality of bands;an error diffusion process portion that carries out an error diffusion process on each divided band to quantize each pixel; anda controlling portion that controls the dividing portion and the error diffusion process portion, whereinthe error diffusion process portion follows control by the controlling portion to operate in a first mode and in a second mode, the error diffusion process portion in the first mode repeating an error diffusion process not accompanying quantization given times on each noted pixel included in a given line of the each band, and the error diffusion process portion in the second mode carrying out an error diffusion process on the each band sequentially from a head line of the each band on the basis of an error value obtained in the first mode to put out quantized data.

4. The image processing apparatus of claim 2 or 3, wherein the given line, is the head line of the each band or a line near the head line.

5. The image processing apparatus of claim 2 or 3, wherein the number of surrounding pixels in the first mode is different from the number of surrounding pixels in the second mode.

6. The image processing apparatus of claim 2 or 3, wherein allocations to surrounding pixels in the first mode are different from allocations to surrounding pixels in the second mode.

7. The image processing apparatus of claim 2 or 3, comprising an image forming portion, wherein when another image data is processed between pages of an image data for image formation at the image forming portion, the error diffusion process portion follows control by the controlling portion to carry out an error diffusion process page by page on the image data, and to carry out an error diffusion process band by band on the other image data between the pages of the image data.

8. An error diffusion processing method of diffusing an error to surrounding pixels when input multivalue image data is converted into image data having tones fewer than that of the original input multivalue image data, the error being an error between a tone value of each pixel of the converted image data and a tone value of each pixel of the input multivalue image data, the method comprising the steps of: dividing the input multivalue image data into a plurality of bands;repeating an error diffusion process not accompanying quantization given times on each noted pixel included in a given line of the each divided band; andcarrying out an error diffusion process on the each band sequentially from a head line of the each band on the basis of an error value obtained from the repeated error diffusion process to put out quantized data.

9. A program for executing the error diffusion processing method of claim 8.