Back to results
US 6,389,162 B2Granted
Image processing apparatus and method and medium
AssigneeCanon Kabushiki Kaisha
InventorMitsuru Maeda
Life of this patent
Estimating the term…
Abstract
There are provided an image processing apparatus and method which can properly determine the number of quantization levels for quantizing image data by properly removing noise from the background of the image data. A histogram forming unit forms the output frequency distribution of densities of image data. A background density width detecting unit determines a density area exhibiting output frequency values equal to or larger than a predetermined threshold and including a maximum output frequency value in the formed distribution. A quantization level count determining unit decides the number of quantization levels on the basis of the number of maximum values included in the distribution other than the determined density area.
Claims30
An image processing apparatus comprising:
- input means for inputting multi-level image data representing an image;
- extracting means for extracting binary image data from the multi-level image data;
- dividing means for dividing the image into a plurality of blocks based on the binary image data;
- deciding means for deciding a number of quantization levels to be utilized for quantization processing for each of the plurality of blocks based on the binary image data;
- and
- quantizing means for quantizing the multi-level image data in each of said blocks by using the number of quantization levels decided by the deciding means, said quantizing means comprising forming means for forming frequency histograms of said multi-level image data in units of said blocks, wherein the number of quantization levels is determined on the basis of the frequency histograms,
- wherein the multi-level image data is constituted by a plurality of color component data, and wherein said binary image data is extracted by the extracting means on the basis of a distribution of said multi-level image data, said distribution being examined on the basis of the frequency histograms of said multi-level image data.
4 more elements
An image processing method comprising:
- an input step of inputting multi-level image data representing an image;
- an extraction step of extracting binary image data from the multi-level image data;
- a division step of dividing the image into a plurality of blocks based on the binary image data;
- a deciding step of deciding a number of quantization levels to be utilized for quantization processing for each of the plurality of blocks based on the binary image data;
- and
- a quantization step of quantizing the multi-level image data in each of said blocks by using the number of quantization levels by deciding step, said quantizing step comprising a forming step for forming frequency histograms of said multi-level image data in units of said blocks, wherein the number of quantization levels is determined on the basis of the frequency histograms,
- wherein the multi-level image data is constituted by a plurality of color component data, and wherein said binary image data is extracted by the extracting step on the basis of a distribution of said multi-level image data, said distribution being examined on the basis of the frequency histograms of said multi-level image data.
4 more elements
A computer readable memory that stores program codes of image processing, comprising:
- a program code of an input step of inputting multi-level image data representing an image;
- a program code of an extraction step of extracting binary image data from the multi-level image data;
- a program code of a division step of dividing the image into a plurality of blocks based on the binary image data;
- a program code of a deciding step of deciding a number of quantization levels to be utilized for quantization processing for each of the plurality of blocks based on the binary image data;
- and
- a program of quantization step of quantizing the multi-level image data in each of said blocks by using the number of quantization levels decided by deciding step, said quantization step comprising a forming step for forming frequency histograms of said multi-level image data in units of said blocks, wherein the number of quantization levels is determined on the basis of the frequency histograms,
- wherein the multi-level image data is constituted by a plurality of color component data, and wherein said binary image data is extracted by the extracting step on the basis of a distribution of said multi-level image data, said distribution being examined on the basis of the frequency histograms of said multi-level image data.
4 more elements
An image processing apparatus comprising:
- forming means for forming a frequency distribution of densities of image data;
- calculating means for calculating a predetermined threshold on the basis of the distribution formed by said forming means;
- extracting means for extracting a density exhibiting maximum frequency value in the distribution formed by said forming means;
- determining means for determining a density area exhibiting frequency values not less than the threshold and including the density exhibiting the maximum frequency value;
- and
- output means for uniformly outputting densities of the image data which have densities within the density area as densities exhibiting the maximum frequency value,
- wherein the image data is color image data.
4 more elements
An image processing method comprising:
- a formation step of forming a frequency distribution of densities of image data;
- a calculation step of calculating a predetermined threshold on the basis of the distribution formed in said formation step;
- an extraction step of extracting a density exhibiting a maximum frequency value in the distribution formed in said formation step;
- a determination step of determining a density area exhibiting frequency values not less than the threshold and including the density exhibiting the maximum frequency value;
- and
- an output step of uniformly outputting densities of the image data which have densities within the density area as densities exhibiting the maximum frequency value,
- wherein the image data is color image data.
4 more elements
A computer readable memory that stores program codes of an image processing, comprising:
- a program code of a formation step of forming a frequency distribution of densities of image data;
- a program code of a calculation step of calculating a predetermined threshold on the basis of the distribution formed in said formation step;
- a program code of an extraction step of extracting a density exhibiting a maximum frequency value in the distribution formed in said formation step;
- a program code of a determination step of determining a density area exhibiting frequency values not less than the threshold and including the density exhibiting the maximum frequency value;
- and
- a program code of an output step of uniformly outputting densities of the image data which have densities within the density area as densities exhibiting the maximum frequency value,
- wherein the image data is color image data.
4 more elements
An image processing apparatus comprising:
- forming means for forming a frequency distribution of densities of image data;
- determining menas for determining a density area exhibiting frequency values not less than a predetermined threshold and including a maximum frequency value in the distribution formed by said forming means;
- and
- first deciding means for deciding numbers of quantization levels on the basis of a number of maximum values included in the distribution other than the density area determined by said determining means.
1 more element
An image processing method comprising:
- a formation step of forming a frequency distribution of densities of image data;
- a determination step of determining a density area exhibiting frequency values not less than a predetermined threshold and including a maximum frequency value in the distribution formed at said formation step;
- and
- a first decision step of deciding numbers of quantization levels on a basis of the number of maximum values included in the distribution other than the density area determined at said determination step.
1 more element
A computer readable memory that stores program codes of an image processing, comprising:
- a program code of a formation step of forming a frequency distribution of densities of image data;
- a program code of a determination step of determining a density area exhibiting frequency values not less than a predetermined threshold and including a maximum frequency value in the distribution formed at said formation step;
- and
- a program code of a first decision step of deciding numbers of quantization levels on the basis of a number of maximum values included in the distribution other than the density area determined at said determination step.
1 more element
Dependencies are inferred from the claim text.