Image processing method, and image processor and storage medium thereof
The present invention relates to an image processing method using the error diffusion method to prevent jumps in a highlight part and darkening in a shadow part at high resolution. The image processing method comprises a step of calculating an average value of density values of N×M (N, M>1) pixels, a step of adding the average value and a diffused quantization error value, a step of quantizing the addition result with a predetermined number of tones, a step of selecting a quantization pattern corresponding to the quantization result, and a step of calculating the diffused quantization error value from the quantization error. The error diffusion algorithm has flexibility in outputting dots. In other words, error diffusion processing is performed in N×M pixel units, and a plurality of quantization patterns are provided, and a quantization pattern is selected based on the quantization result. Therefore jumps in a highlight part and smears in a shadow part can be prevented, the tone maintenance characteristic unique to the error diffusion can be satisfied, and a smooth and sharp image can be obtained.
1. An image processing method for performing image processing on input images using an error diffusion method, comprising:
a step of calculating an average value of density values of N×M (N, M>1) pixels;
a step of adding said average value and a diffused quantization error value;
a step of quantizing said addition result by a predetermined number of tones;
a step of selecting a quantization pattern corresponding to said quantization result;
a step of calculating said diffused quantization error value from a quantization error;
a step of calculating a density gradient of said N×M area; and
a step of selecting a quantization pattern from said quantization result and
said density gradient.
2. An image processing method for performing image processing on input images using an error diffusion method, comprising:
a step of calculating an average value of density values of N×M (N, M>1) pixels;
a step of adding said average value and a diffused quantization error value;
a step of quantizing said addition result by a predetermined number of tones;
a step of selecting a quantization pattern corresponding to said quantization result;
a step of calculating said diffused quantization error value from a quantization error, wherein said selecting step comprises a step of selecting a quantization pattern corresponding to said quantization result from a plurality of quantization patterns which do not have an isolated dot.
3. An image processing method for performing image processing on input images using an error diffusion method, comprising:
a step of calculating an average value of density values of N×M (N, M>1) pixels;
a step of adding said average value and a diffused quantization error value;
a step of quantizing said addition result by a predetermined number of tones;
a step of selecting a quantization pattern corresponding to said quantization result;
a step of calculating said diffused quantization error value from a quantization error; and
a step of performing pulse width modulation on said quantization pattern.
4. An image processor for performing image processing on input images using an error diffusion method, comprising:
a memory for storing said input images; and
a processing unit for performing image processing on said input images, wherein said processing unit adds an average value of density values of N×M (N, M>1) pixels and
a diffused quantization error value, quantizes said addition result with a predetermined number of tones, calculates the density gradient in said N×M area, selects a quantization pattern from said result and said density gradient quantization, and calculates said diffused quantization error value from a quantization error.
5. An image processor for performing image processing on input images using an error diffusion method, comprising:
a memory for storing said input images; and
a processing unit for performing image processing on said input images, wherein said processing unit adds an average value of density values of N×M (N, M>1) pixels and
a diffused quantization error value, quantizes said addition result with a predetermined number of tones, selects quantization pattern corresponding to said quantization result from a plurality of quantization patterns which do not have an isolated dot, and calculates said diffused quantization error value from a quantization error.
6. An image processor for performing image processing on input images using an error diffusion method, comprising:
a memory for storing said input images;
a processing unit for performing image processing on said input images, wherein said processing unit adds an average value of density values of N×M (N, M>1) pixels
a diffused quantization error value, quantizes said addition result with a predetermined number of tones, then selects a quantization pattern corresponding to said quantization result, and calculates said diffused quantization error value from a quantization error, and
a pulse width modulation circuit which performs pulse width modulation on said quantization pattern.
7. A computer readable storage medium for storing a program to perform image processing on input images using an error diffusion method, wherein said program comprises:
a program for calculating an average value of density values of N×M (N, M>1) pixels, and adding said average value and a diffused quantization error value;
a program for quantizing said addition result with a predetermined number of tones, and selecting a quantization pattern corresponding to said quantization result;
a program for calculating said diffused quantization error value from a quantization error; and
a program for calculating the density gradient in said N×M area, and selecting a quantization pattern from said quantization result and said density gradient.
8. A computer readable storage medium for storing a program to perform image processing on input images using an error diffusion method, wherein said program comprises:
a program for calculating an average value of density values of N×M (N, M>1) pixels, and adding said average value and a diffused quantization error value;
a program for quantizing said addition result with a predetermined number of tones, and selecting a quantization pattern corresponding to said quantization result;
a program for calculating said diffused quantization error value from a quantization error; and
a program for selecting a quantization pattern corresponding to said quantization result from a plurality of quantization patterns which do not have an isolated dot.
9. A computer readable storage medium for storing a program to perform image processing on input images using an error diffusion method, wherein said program comprises:
a program for calculating an average value of density values of N×M (N, M>1) pixels, and adding said average value and a diffused quantization error value;
a program for quantizing said addition result with a predetermined number of tones, and selecting a quantization pattern corresponding to said quantization result;
a program for calculating said diffused quantization error value from a quantization error; and
a program for performing pulse width modulation on said quantization pattern.