Image quality in error diffusion scheme

An image processing device for converting multi-level-image data into binary-image data by using one of a least average error method and an error diffusion method, comprising:

• an image-data-correction unit which corrects multi-level-image data of a current pixel by adding thereto an error diffused from surrounding binarized pixels so as to output corrected-image data;
• a binarizing unit which binarizes the corrected-image data by comparing the corrected-image data with a predetermined threshold;
• an error-calculation unit which calculates an error of the current pixel based on the corrected image data and a result of the binarization;
• and
• an error-correction unit which corrects errors of surrounding pixels when the result of the binarization of the current pixel represents a predetermined one of either a black dot or a white hole,
• wherein said error-correction unit corrects the errors of surrounding pixels when the result of the binarization of the current pixel represents a black dot, and
• wherein said error-correction unit corrects the errors of surrounding pixels to an extent that varies depending on the multi-level-image data of the current pixel.

The image processing device for converting multi-level-image data into binary-image data by using one of a least average error method and an error diffusion method, comprising:

• an image-data-correction unit which corrects multi-level-image data of a current pixel by adding thereto an error diffused from surrounding binarized pixels so as to output corrected-image data;
• a binarizing unit which binarizes the corrected-image data by comparing the corrected-image data with a predetermined threshold;
• an error-calculation unit which calculates an error of the current pixel based on the corrected image data and a result of the binarization;
• and
• an error-correction unit which corrects errors of surrounding pixels when the result of the binarization of the current pixel represents a predetermined one of either a black dot or a white hole,
• wherein said error-correction unit corrects the errors of surrounding pixels when the result of the binarization of the current pixel represents a black dot, and
• wherein said error-correction unit corrects the errors of surrounding pixels, a number of the surrounding pixels varying depending on the multilevel-image data of the current pixel.

A method of converting multi-level-image data into binary-image data by using one of a least average error method and an error diffusion method, comprising the steps of:

• correcting multi-level-image data of a current pixel by adding thereto an error diffused from surrounding binarized pixels so as to output corrected-image data;
• binarizing the corrected-image data by comparing the corrected-image data with a predetermined threshold;
• calculating an error of the current pixel based on the corrected-image data and a result of the binarization;
• and
• correcting errors of surrounding pixels when the result of the binarization of the current pixel represents a predetermined one of a black dot and a white hole, and refraining from correcting the errors of the surrounding pixels when the result of the binarization of the current pixel represents another one of the black dot and the white hole.

The method of converting multi-level-image data into binary-image data by using one of a least average error method and an error diffusion method, comprising the steps of:

• correcting multi-level-image data of a current pixel by adding thereto an error diffused from surrounding binarized pixels so as to output corrected-image data;
• binarizing the corrected-image data by comparing the corrected-image data with a predetermined threshold;
• calculating an error of the current pixel based on the corrected-image data and a result of the binarization;
• and
• correcting errors of surrounding pixels when the result of the binarization of the current pixel represents a predetermined one of either a black dot or a white hole,
• wherein said step of correcting errors corrects the errors of surrounding pixels when the result of the binarization of the current pixel represents a black dot, and
• wherein said step of correcting errors corrects the errors of surrounding pixels to an extent that varies depending on the multi-level-image data of the current pixel.

The method of converting multi-level-image data into binary-image data by using one of a least average error method and an error diffusion method, comprising the steps of:

• correcting multi-level-image data of a current pixel by adding thereto an error diffused from surrounding binarized pixels so as to output corrected-image data;
• binarizing the corrected-image data by comparing the corrected-image data with a predetermined threshold;
• calculating an error of the current pixel based on the corrected-image data and a result of the binarization;
• and
• correcting errors of surrounding pixels when the result of the binarization of the current pixel represents a predetermined one of either a black dot or a white hole,
• wherein said step of correcting errors corrects the errors of surrounding pixels when the result of the binarization of the current pixel represents a black dot, and
• wherein said step of correcting errors corrects the errors of surrounding pixels, a number of the surrounding pixels varying depending on the multilevel-image data of the current pixel.

A memory medium having a program embodied therein for causing a computer to convert multi-level-image data into binary-image data by using one of a least average error method and an error diffusion method, said program comprising:

• an image-data-correction unit configured to correct multi-level-image data of a current pixel by adding thereto an error diffused from surrounding binarized pixels so as to output corrected-image data;
• a binarizing unit configured to binarize the corrected-image data by comparing the corrected-image data with a predetermined threshold;
• an error-calculation unit configured to calculate an error of the current pixel based on the corrected-image data and a result of the binarization;
• and
• an error-correction unit configured to correct errors of surrounding pixels when the result of the binarization of the current pixel represents a predetermined one of a black dot and a white hole, and configured to refrain from correcting the errors of the surrounding pixels when the result of the binarization of the current pixel represents another one of the black dot and the white hole.

The memory medium having a program embodied therein for causing a computer to convert multi-level-image data into binary-image data by using one of a least average error method and an error diffusion method, said program comprising:

• an image-data-correction unit configured to correct multi-level-image data of a current pixel by adding thereto an error diffused from surrounding binarized pixels so as to output corrected-image data;
• a binarizing unit configured to binarize the corrected-image data by comparing the corrected-image data with a predetermined threshold;
• an error-calculation unit configured to calculate an error of the current pixel based on the corrected-image data and a result of the binarization;
• and
• an error-correction unit configured to correct errors of surrounding pixels when the result of the binarization of the current pixel represents a predetermined one of either a black dot or a white hole,
• wherein said error-correction unit corrects the errors of surrounding pixels when the result of the binarization of the current pixel represents a black dot, and
• wherein said error-correction unit corrects the errors of surrounding pixels to an extent that varies depending on the multi-level-image data of the current pixel.

The memory medium having a program embodied therein for causing a computer to convert multi-level-image data into binary-image data by using one of a least average error method and an error diffusion method, said program comprising:

• an image-data-correction unit configured to correct multi-level-image data of a current pixel by adding thereto an error diffused from surrounding binarized pixels so as to output corrected-image data;
• a binarizing unit configured to binarize the corrected-image data by comparing the corrected-image data with a predetermined threshold;
• an error-calculation unit configured to calculate an error of the current pixel based on the corrected-image data and a result of the binarization;
• and
• an error-correction unit configured to correct errors of surrounding pixels when the result of the binarization of the current pixel represents a predetermined one of either a black dot or a white hole,
• wherein said error-correction unit corrects the errors of surrounding pixels when the result of the binarization of the current pixel represents a black dot, and
• wherein said error-correction unit corrects the errors of surrounding pixels, a number of the surrounding pixels varying depending on the multilevel-image data of the current pixel.