Inverse halftoning using inverse projection of predicted errors for multi-bit images

A method comprising:

• converting an original image into a halftone image having a lower bit count per pixel, said halftone image having pixel error based on said lower bit count per pixel, said converting diffusing said pixel error of each pixel of said halftone image to adjacent pixels using an error weighting matrix, said halftone image and consuming less storage and data processing resources relative to said original image;
• receiving said halftone image represented in an halftone image matrix into an image path of a printing device;
• and
• processing said halftone image through said image path to produce a grayscale image from said halftone image, said image path having storage and data processing constraints that prevent said image path from processing said original image, said storage and data processing constraints allow said image path to process said halftone image, and said processing comprising:
• determining, using said error weighting matrix, for each pixel in said halftone image, an amount of error added based on said adjacent pixels during said converting by processing each pixel individually, starting with a last matrix location at the end of said halftone image matrix and progressing back, pixel-by-pixel, to a first matrix location at the beginning of said halftone image matrix;
• removing, from each pixel in said halftone image, said amount of error added based on said adjacent pixels by processing each pixel individually, starting with said last matrix location at the end of said halftone image matrix and progressing back, pixel-by-pixel, to said first matrix location at the beginning of said halftone image matrix;
• and
• reconstructing said halftone image using a filter after said removing said amount of error added based on said adjacent pixels from all pixels in said halftone image to produce said grayscale image,
• said filter comprising a low-pass matrix filter,
• said reconstructing:
• using said low-pass matrix filter to multiply numerical values of said low-pass matrix filter by corresponding underlying pixel values of pixels adjacent a center pixel over which said low-pass matrix filter is centered to produce products;
• adding said products together to produce a sum;
• and
• multiplying said sum by a reciprocal of a total of said low-pass matrix filter values to produce a resulting value of said center pixel, and
• said reconstructing producing pixels having a higher bit count per pixel relative to said lower bit count per pixel of said halftone image.

An image processing apparatus comprising:

• an image processor converting an original image into an input image having a lower bit count per pixel, said input image having pixel error based on said lower bit count per pixel, said converting diffusing said pixel error of each pixel of said input image to adjacent pixels using an error weighting matrix, said input image and consuming less storage and data processing resources relative to said original image, and said image processor comprises an image path;
• an input receiving said input image represented in an input image matrix, said image processor being directly or indirectly connected to said input;
• a filter directly or indirectly connected to said image processor;
• and
• an output directly or indirectly connected to said image processor,
• said image processor producing an output image from said input image,
• said output outputting said output image,
• said image path having storage and data processing constraints that prevent said image path from processing said original image, said storage and data processing constraints allow said image path to process said input image,
• said image processor producing said output image from said input image by:
• determining, using said error weighting matrix, for each pixel in said input image, an amount of error added based on said adjacent pixels during said converting by processing each pixel individually, starting with a last matrix location at the end of said input image matrix and progressing back, pixel-by-pixel, to a first matrix location at the beginning of said input image matrix;
• removing, from each pixel in said input image, said amount of error added based on said adjacent pixels by processing each pixel individually, starting with said last matrix location at the end of said input image matrix and progressing back, pixel-by-pixel, to said first matrix location at the beginning of said input image matrix;
• and
• reconstructing said input image using said filter after completing said removing said amount of error added based on said adjacent pixels from all pixels in said input image to produce said output image,
• said filter comprising a low-pass matrix filter
• said image processor performing said reconstructing by:
• using said low-pass matrix filter to multiply numerical values of said low-pass matrix filter by corresponding underlying pixel values of pixels adjacent a center pixel over which said low-pass matrix filter is centered to produce products;
• adding said products together to produce a sum;
• and
• multiplying said sum by a reciprocal of a total of said low-pass matrix filter values to produce a resulting value of said center pixel, and
• said image processor performing said reconstructing by producing pixels having a higher bit count per pixel relative to said lower bit count per pixel of said input image.

An image processing apparatus comprising:

• an image processor converting an original image into an halftone image having a lower bit count per pixel, said halftone image having pixel error based on said lower bit count per pixel, said converting diffusing said pixel error of each pixel of said halftone image to adjacent pixels using an error weighting matrix, said halftone image and consuming less storage and data processing resources relative to said original image, and said image processor comprises an image path;
• an input receiving said halftone image represented in an halftone image matrix, said image processor directly or indirectly connected to said input;
• a filter directly or indirectly connected to said image processor;
• and
• an output directly or indirectly connected to said image processor,
• said image processor producing a gray scale image from said halftone image,
• said output outputting said gray scale image,
• said image path having storage and data processing constraints that prevent said image path from processing said original image, said storage and data processing constraints allow said image path to process said halftone image,
• said image processor producing said gray scale image from said halftone image by:
• determining, using said error weighting matrix, for each pixel in said halftone image, an amount of error added based on said adjacent pixels during said converting by processing each pixel individually, starting with a last matrix location at the end of said halftone image matrix and progressing back, pixel-by-pixel, to a first matrix location at the beginning of said halftone image matrix;
• removing, from each pixel in said halftone image, said amount of error added based on said adjacent pixels by processing each pixel individually, starting with said last matrix location at the end of said halftone image matrix and progressing back, pixel-by-pixel, to said first matrix location at the beginning of said halftone image matrix;
• and
• reconstructing said halftone image using said filter after completing said removing said amount of error added based on said adjacent pixels from all pixels in said halftone image to produce said grayscale image,
• said filter comprising a low-pass matrix filter,
• said image processor performing said reconstructing by:
• using said low-pass matrix filter to multiply numerical values of said low-pass matrix filter by corresponding underlying pixel values of pixels adjacent a center pixel over which said low-pass matrix filter is centered to produce products;
• adding said products together to produce a sum;
• and
• multiplying said sum by a reciprocal of a total of said low-pass matrix filter values to produce a resulting value of said center pixel, and
• said image processor performing said reconstructing by producing pixels having a higher bit count per pixel relative to said lower bit count per pixel of said halftone image.