Rotation and scale invariant image finder

A computer program product for use in a computer system adapted for pattern matching of a digital reference image template comprising:

• a computer useable medium having computer readable program code adapted for computing an optimal sparse pixel set indicative of a reference image template embodied thereon, said computer program product further including:
• computer readable program code for computing an initial sparse pixel set from a subset of said pixels in said reference image template;
• computer readable program code for initializing, by storing in an optimal pixel accumulator set, said initial sparse pixel set;
• computer readable program code for correlating said optimal pixel accumulator set with said reference image template and said search image scene to determine a candidate optimal pixel based on a correlation score from the subset of pixels of said reference image template not already in said optimal pixel accumulator set;
• computer readable program code for storing, in said optimal pixel accumulator set, said candidate optimal pixel if said candidate optimal pixel is highly influential on said correlation score;
• computer readable program code for building, from among the remaining pixels of said reference image template, said optimal pixel accumulator set by repeating said correlating and said storing;
• computer readable program code for terminating said building when said accumulator sparse pixel set contains an optimal set of pixels according to predetermined accumulation optimization logic;
• and
• computer readable program code for storing, in said optimal sparse pixel set said optimal pixel accumulator set.

A method of digital image recognition for finding a reference image template in a search image scene through grayscale correlation matching comprising the steps of:

• providing a reference image template represented as a pixelated grayscale digital image;
• providing a search image scene represented as a pixelated grayscale digital image;
• computing an optimal sparse pixel set indicative of said reference image template by the further steps of:
• computing an initial sparse pixel set from a subset of said pixels in said reference image template;
• initializing, by storing in an optimal pixel accumulator set, said initial sparse pixel set;
• correlating said optimal pixel accumulator set with said reference image template and said search image scene to determine a candidate optimal pixel based on a correlation score from the subset of pixels of said reference image template not already in said optimal pixel accumulator set;
• storing, in said optimal pixel accumulator set, said candidate optimal pixel if said candidate optimal pixel is highly correlation sensitive;
• building, from among the remaining pixels of said reference image template, said optimal pixel accumulator set by repeating said correlating and said storing steps;
• terminating said building when said accumulator sparse pixel set contains an optimal set of pixels according to predetermined accumulation optimization logic;
• and
• storing, in said optimal sparse pixel set, said optimal pixel accumulator set;
• locating, within said search image scene, said reference image template by correlating said optimal sparse pixel set with said search image scene.

A computer apparatus for pattern matching of pixelated digital images comprising:

• a reference image memory for storing a pixelated reference image template comprising a plurality of pixels in a matrix;
• and
• a search scene memory for storing a pixelated search image template comprising a plurality of pixels in a matrix, wherein each of said pixels has a grayscale and a position;
• an optimal sparse pixel memory adapted to store a subset of said pixels of said reference image template;
• and
• a processor adapted to determine a correlation score of a plurality of pixels, wherein said correlation results are indicative of a pattern match between said reference image template and said search scene image, said correlation results being determined by sequentially copying a plurality of said pixels from said optimal sparse pixel memory and a plurality of said pixels from said search image memory into said processor for comparing said grayscale values and said positions,
• wherein said pixels are selectively stored in said optimal sparse pixel memory as a result of a correlation score which is highly influential in determining said pattern match.