Patent ID: 7729546

Claim:
A method for compressing an array of pixels representing image data, wherein each pixel in said array has an associated intensity value, comprising: identifying an N-by-N window centered upon a selected pixel of said array of pixels; evaluating at least one pixel in said N-by-N window to determine whether said selected pixel is a potential text element, wherein said evaluating comprises: summing said intensity values of each pixel in a row for each row of pixels within said N-by-N window and identifying a row having a maximum total intensity and a row having a minimum total intensity, wherein a difference between said maximum total intensity of said row and said minimum total intensity of said row is compared to a first predetermined threshold value; summing said intensity values of each pixel in a column for each column of pixels within said N-by-N window and identifying a column having a maximum total intensity and a column having a minimum total intensity, wherein a difference between said maximum total intensity of said column and said minimum total intensity of said column is compared to a second predetermined threshold value; and summing said intensity values of each pixel in a first major diagonal of said N-by-N window to obtain a first diagonal total intensity, summing said intensity values of each pixel in a second major diagonal of said N-by-N window to obtain a second diagonal total intensity and comparing a difference between said first diagonal total intensity and said second diagonal total intensity against a third predetermined threshold value; after said identifying of said N-by-N window, if said evaluating determines that said selected pixel is a potential text element, then identifying an M-by-M window centered upon said selected pixel such that said M-by-M window is smaller than said N-by-N window; determining whether said potential text element includes text by comparing at least two pixels within said M-by-M window; assigning said selected pixel to a first layer of said plurality of layers if said determining determines that said potential text element includes text; assigning said selected pixel to a second layer of said plurality of layers if said determining determines that said potential text element does not include text; and compressing said first layer using a first compression technique to create a first compressed layer.