Method of changing a color in an image

Claim 1

A method of changing a color in an image, the image being defined by pixels, each pixel having a value indicative of an optical density value of the image at a discrete point therein, and where the image includes lines and background, lines including a set of pixels having optical density values distinct from optical density values of pixels in the background, the method including changing a color of at least one of the lines and the background, characterised by: a) converting the value of each pixel to a combination of a red value, a green value and a blue value, where combinations of red, green and blue values define all possible colors in a color set, and any black value is converted to a combination of a red, a green and a blue value where the red value = green value = blue value; b) selecting a foreground color, identified in terms of red, green and blue values; c) selecting a background color, identified in terms of red, green and blue values; d) comparing the red, green and blue values of each pixel to a reference value; e) determining from said comparison whether the pixel is a background pixel or a foreground pixel; f) setting the value of said pixel equal to the foreground color, identified in terms of red, green and blue values or the background color, identified in terms of red, green and blue values, in accordance with said determination.

Claim 2

A method of changing a color in an image, the image being defined by pixels, each pixel having a value indicative of an optical density value of the image at a discrete point therein, and where the image includes lines and background, lines including a set of pixels having optical density values distinct from optical density values of pixels in the background, the method including changing a color of at least one of the lines and the background, characterised by: a) converting the value of each pixel to a combination of a red value, a green value and a blue value, where combinations of red, green and blue values define all possible colors in a color set, and any black value is converted to a combination of a red, a green and a blue value where the red value = green value = blue value; b) selecting a foreground color, identified in terms of red, green and blue values; c) selecting a background color, identified in terms of red, green and blue values; d) comparing the red, green and blue values of each pixel to a reference value; e) determining from said comparison whether the pixel is a background pixel or a foreground pixel; f) setting the value of said pixel equal to the foreground color, identified in terms of red, green and blue values or the background color, identified in terms of red, green and blue values, in accordance with said determination.

Claim 8

A method of changing a color in an image, the image being defined by a set of pixels, each pixel having a value indicative of an optical density value of the image at a discrete point therein in terms of gray values varying over a range of white to black, and wherein the image includes lines and background, lines including a set of pixels having gray values other than white, the method including changing a color of at least one of the lines and the background, and characterised by: a) converting the gray value of each pixel to a combination of red, green and blue values, where combinations of red, green and blue values define all possible colors in a color set, and gray values are converted to a combination of red, green and blue values where the red value = green value = blue value; b) selecting a foreground color, identified in terms of red, green and blue values; c) selecting a background color, identified in terms of red, green and blue values; d) comparing each pixel to a threshold value selected to identify background pixels; e) determining from said comparison whether the pixel is a background pixel; f) for each background pixel so determined, changing said pixel value to the background color; g) for any pixel not determined to be a background pixel, comparing each pixel to a threshold value selected to identify foreground pixels; h) determining from said comparison whether the pixel is a foreground pixel; i) for each foreground pixel so determined, changing said pixel value to the foreground color; and j) for any pixel determined not to be either a foreground pixel or a background pixel, applying neither the foreground or background colors to said pixel.

Claim 9

A method of changing a color in an image, the image being defined by a set of pixels, each pixel having a value indicative of an optical density value of the image at a discrete point therein in terms of gray values varying over a range of white to black, and wherein the image includes lines and background, lines including a set of pixels having gray values other than white, the method including changing a color of at least one of the lines and the background, and characterised by: a) converting the gray value of each pixel to a combination of red, green and blue values, where combinations of red, green and blue values define all possible colors in a color set, and gray values are converted to a combination of red, green and blue values where the red value = green value = blue value; b) selecting a foreground color, identified in terms of red, green and blue values; c) selecting a background color, identified in terms of red, green and blue values; d) comparing each pixel to a threshold value selected to identify background pixels; e) determining from said comparison whether the pixel is a background pixel; f) for each background pixel so determined, changing said pixel value to the background color; g) for any pixel not determined to be a background pixel, comparing each pixel to a threshold value selected to identify foreground pixels; h) determining from said comparison whether the pixel is a foreground pixel; i) for each foreground pixel so determined, changing said pixel value to the foreground color; and j) for any pixel determined not to be either a foreground pixel or a background pixel, applying neither the foreground or background colors to said pixel.

Claim 10

A method of changing a color in an image, the image being defined by a set of pixels in a memory, each pixel having an m-bit gray value indicative of an optical density value of the image at a discrete point therein varying over a range from white to black, and wherein the image includes lines and background, lines including a set of pixels having gray values other than white, the method including changing a color of at least one of the lines and the background, and characterised by: a) for each m-bit pixel value, generating a representative n-bit pixel value, where n<m, and a gray value, and the set of n-bit values defines all possible colors in an image; b) converting the n-bit pixel value of each pixel to an n-bit combination of red, green and blue values, where combinations of red, green and blue values defined all possible colors in a color set, and gray values are converted to an n-bit combination of red, green and blue values where the red value = green value = blue value; b) displaying the image in term of n-bit red, green and blue pixel values; c) selecting a foreground color, identified in terms of n-bit red, green and blue values; d) selecting a background color, identified in terms of n-bit red, green and blue values; e) comparing each n-bit combination of red, green and blue values to a threshold value selected to identify background combination of red, green and blue values; f) determining from said comparison whether the n-bit combination of red, green and blue value is a background color; g) for each background color so determined, changing said n-bit red, green and blue pixel value to the background color; h) changing all n-bit red, green and blue pixel values not identified as background pixels to the foreground color; and i) redisplaying the the image in terms of red, green and blue pixel values in accordance with any red, green and blue pixel value changes.

Claim 11

A method of changing a color in an image, the image being defined by a set of pixels in a memory, each pixel having an m-bit gray value indicative of an optical density value of the image at a discrete point therein varying over a range from white to black, and wherein the image includes lines and background, lines including a set of pixels having gray values other than white, the method including changing a color of at least one of the lines and the background, and characterised by: a) for each m-bit pixel value, generating a representative n-bit pixel value, where n<m, and a gray value, and the set of n-bit values defines all possible colors in an image; b) converting the n-bit pixel value of each pixel to an n-bit combination of red, green and blue values, where combinations of red, green and blue values defined all possible colors in a color set, and gray values are converted to an n-bit combination of red, green and blue values where the red value = green value = blue value; b) displaying the image in term of n-bit red, green and blue pixel values; c) selecting a foreground color, identified in terms of n-bit red, green and blue values; d) selecting a background color, identified in terms of n-bit red, green and blue values; e) comparing each n-bit combination of red, green and blue values to a threshold value selected to identify background combination of red, green and blue values; f) determining from said comparison whether the n-bit combination of red, green and blue value is a background color; g) for each background color so determined, changing said n-bit red, green and blue pixel value to the background color; h) changing all n-bit red, green and blue pixel values not identified as background pixels to the foreground color; and i) redisplaying the the image in terms of red, green and blue pixel values in accordance with any red, green and blue pixel value changes.