Systems and methods for rank-order error diffusion image processing

A method of halftoning an image, the method comprising:

• receiving the image, the received image being at an input resolution;
• resampling the image to a processing resolution if the input resolution and the processing resolution are not the same;
• processing the image using rank-ordered error diffusion;
• and
• resampling the processed image to an output resolution for the image if the processing resolution and the output resolution are not the same,
• wherein the rank-ordered error diffusion includes
• selecting a diffusion mask encompassing pixels that have not yet been processed, the mask relating to a target pixel and pixels neighboring thereto;
• receiving a first pair of neighboring pixel values for a first pixel pair including a first neighboring pixel and a second neighboring pixel;
• receiving a second pair of neighboring pixel values for a second pixel pair including a third neighboring pixel and a fourth neighboring pixel;
• determining a ranking order of the first, second, third and fourth neighboring pixels by comparing the first neighboring pixel value with the second neighboring pixel value and comparing the third neighboring pixel and the fourth neighboring pixel, where the first neighboring pixel and the second neighboring pixel are closer to the target pixel than the third neighboring pixel and the fourth neighboring pixel;
• and
• diffusing error to at least one of the first, second, third and fourth neighboring pixels based on the determined ranking order of the first, second, third and fourth neighboring pixels.

A halftoning apparatus, comprising:

• an image receiving unit;
• and
• a rank-order error diffusion processing unit that receives a grayed halftone image from the image receiving unit and processes the receiving grayed halftone image to output a renderable version of the received grayed halftone image which has been subjected to rank-order error diffusion,
• wherein the rank-order error diffusion unit resamples the received grayed image to a processing resolution if an input resolution of the received grayed image and the processing resolution are not the same, the processing resolution being a resolution at which the received grayed image is subjected to processing by the rank-order error diffusion processing unit,
• wherein the rank-order error diffusion processing unit
• selects a diffusion mask encompassing pixels that have not yet been processed, the mask relating to a target pixel and pixels neighboring thereto;
• receives a first pair of neighboring pixel values for a first pixel pair including a first neighboring pixel and a second neighboring pixel;
• receives a second pair of neighboring pixel values for a second pixel pair including a third neighboring pixel and a fourth neighboring pixel;
• determines a ranking order of the first, second, third and fourth neighboring pixels by comparing the first neighboring pixel value with the second neighboring pixel value and comparing the third neighboring pixel and the fourth neighboring pixel, where the first neighboring pixel and the second neighboring pixel are closer to the target pixel than the third neighboring pixel and the fourth neighboring pixel;
• and
• diffuses error to at least one of the first, second, third and fourth neighboring pixels based on the determined ranking order of the first, second, third and fourth neighboring pixels.