Digital image processing device for enlarging original image with high fidelity

Claim 1

An image processing device for producing second digital data based upon first digital data, wherein the first digital data represents an original image composed of a first multiplicity of pixels arranged in row and column, each pixel having a density value, and the second digital data represents a C-by-C times enlarged image relative to a size of the original image, the C-by-C times enlarged image being composed of a second multiplicity of pixels arranged in row and column, each pixel having a density value, said device comprising: storing means for storing the first digital data; first computing means for computing a first approximate surface approximate to a surface covering all density values of first control points, a group of A-by-A adjacent pixels arranged in row and column being selected as the first control points from the first multiplicity of pixels, the first approximate surface having a center portion. A being an interger equal to or greater than 2; first enlarging means for producing a 2-by-2 times enlarged center portion while sampling the center portion of the first approximate surface to obtain 2-by-2 sampled values; second computing means for computing third digital data representative of a 2-by-2 times enlarged image by non-overlappingly combining the 2-by-2 times enlarged center portions produced by said first computing means and said first enlarging means while selecting different groups of A-by-A adjacent pixels arranged in row and column, said different groups of A-by-A adjacent pixels being displaced on pixel-to-pixel basis from said group of A-by-A adjacent pixels in directions of row and column, the 2-by-2 times enlarged image being composed of a third multiplicity of pixels arranged in row and column; third computing means for computing a second approximate surface approximate to a surface covering all density values of second control points, a group of B-by-B pixels arranged alternately in row and column being selected as the second control points from the third multiplicity of pixels, the second approximate surface having a center portion corresponding to the center portion of the first approximate surface, B being an integer equal to or greater than 2; second enlarging means for producing a C-by-C times enlarged center portion while sampling the center portion of the second approximate surface to obtain C-by-C sampled values, C being an integer equal to or greater than 2; and fourth computing means for computing the second digital data, wherein four C-by-C times enlarged center portions are produced by said third computing means and said second enlarging means with respect to each of the first multiplicity of pixels while selecting different groups of B-by-B pixels arranged alternately in row and column, said different groups of B-by-B alternately arranged pixels being displaced from said group of B-by-B alternately arranged pixels by one pixel in directions of row, column, and row and column, and an average value of four C-by-C times enlarged center portions is used as a basis for the second digital data.