IMAGE PROCESSING APPARATUS, IMAGE FORMING APPARATUS, AND IMAGE PROCESSING METHOD
First Claim
1. An image processing apparatus for scanning each pixel of an input image data in a raster order so as to quantize a multi-valued input pixel signal of said each pixel by using an error diffusion method, the image processing apparatus comprising:
- an error adding section for calculating an additional value by adding an input pixel value of a quantization-target pixel to a diffusion error diffused from a quantized pixel;
a quantizing section for calculating an output pixel value of the quantization-target pixel by quantizing the quantization-target pixel based on a result of comparison between the additional value and a threshold value;
an error calculating section for calculating a quantization error based on the input pixel value, the additional value, and the output pixel value obtained by the quantization of the quantization-target pixel;
a diffusion error calculating section for calculating a diffusion error to be diffused to a non-quantized pixel based on the quantization error and a positional relation between the quantization-target pixel and the non-quantized pixel;
an adjustment standard value generating section for setting an adjustment standard value for every quantization-target pixel according to the output pixel value of the quantization-target pixel, the adjustment standard value providing a standard of correction of the additional value or the threshold value at a time of quantization of the non-quantized pixel;
an adjustment value calculating section for calculating an adjustment value to be used in quantizing the quantization-target pixel, the adjustment value calculating section calculating the adjustment value by attenuating, according to a distance between the quantized pixel and the quantization-target pixel, the adjustment standard value set for the quantized pixel; and
a threshold value correcting section for correcting, based on the adjustment value, the threshold value or the additional value used in quantizing the quantization-target pixel.
1 Assignment
0 Petitions
Accused Products
Abstract
An image processing apparatus includes (i) a repulsive force generating section for setting repulsive force values RVa and RVu of a quantized pixel according to an output pixel value of the quantized pixel, (ii) a repulsive force calculating section for calculating a repulsive force value RVC to be used in quantizing a quantization-target pixel by attenuating, according to a distance between the quantized pixel and the quantization-target pixel, the repulsive force values RVa and RVu set for the quantized pixel; and (iii) a threshold value correcting section for correcting a threshold value T used in quantizing the quantization-target pixel according to the repulsive force value RVC. This makes it possible to prevent an increase in the number of processing steps and amount of processing when an image is processed with an error diffusion method. At the same time, it is possible to prevent decrease in image uniformity and formation of a pattern unique to the error diffusion method.
26 Citations
11 Claims
-
1. An image processing apparatus for scanning each pixel of an input image data in a raster order so as to quantize a multi-valued input pixel signal of said each pixel by using an error diffusion method, the image processing apparatus comprising:
-
an error adding section for calculating an additional value by adding an input pixel value of a quantization-target pixel to a diffusion error diffused from a quantized pixel; a quantizing section for calculating an output pixel value of the quantization-target pixel by quantizing the quantization-target pixel based on a result of comparison between the additional value and a threshold value; an error calculating section for calculating a quantization error based on the input pixel value, the additional value, and the output pixel value obtained by the quantization of the quantization-target pixel; a diffusion error calculating section for calculating a diffusion error to be diffused to a non-quantized pixel based on the quantization error and a positional relation between the quantization-target pixel and the non-quantized pixel; an adjustment standard value generating section for setting an adjustment standard value for every quantization-target pixel according to the output pixel value of the quantization-target pixel, the adjustment standard value providing a standard of correction of the additional value or the threshold value at a time of quantization of the non-quantized pixel; an adjustment value calculating section for calculating an adjustment value to be used in quantizing the quantization-target pixel, the adjustment value calculating section calculating the adjustment value by attenuating, according to a distance between the quantized pixel and the quantization-target pixel, the adjustment standard value set for the quantized pixel; and a threshold value correcting section for correcting, based on the adjustment value, the threshold value or the additional value used in quantizing the quantization-target pixel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 11)
-
-
10. An image processing method for scanning each pixel of an input image data in a raster order so as to quantize a multi-valued input pixel signal of said each pixel by using an error diffusion method, the image processing method comprising:
-
the error adding step for calculating an additional value by adding an input pixel value of a quantization-target pixel to a diffusion error diffused from a quantized pixel; the quantizing step for calculating an output pixel value of the quantization-target pixel by quantizing the quantization-target pixel based on a result of comparison between the additional value and a threshold value; the error calculating step for calculating a quantization error based on the input pixel value, the additional value, and the output pixel value obtained by the quantization of the quantization-target pixel; the diffusion error calculating step for calculating a diffusion error to be diffused to a non-quantized pixel based on the quantization error and a positional relation between the quantization-target pixel and the non-quantized pixel; the adjustment standard value generating step for setting an adjustment standard value for every quantization-target pixel according to the output pixel value of the quantization-target pixel, the adjustment standard value providing a standard of correction of the additional value or the threshold value at a time of quantization of the non-quantized pixel; the adjustment value calculating step for calculating an adjustment value to be used in quantizing the quantization-target pixel, the adjustment value calculating section calculating the adjustment value by attenuating, according to a distance between the quantized pixel and the quantization-target pixel, the adjustment standard value set for the quantized pixel; and the threshold value correcting step for correcting, based on the adjustment value, the threshold value or the additional value used in quantizing the quantization-target pixel.
-
Specification