Image database key generation method

A method of generating a matching key for an image with said matching key being substantially invariant to rotation, scale and translation, said method comprising the steps of:

• forming a multi-channel image of said image by applying an operator to said image, said operator being commutative within a constant to rotation and scale;
• forming a representation of said multi-channel image that is substantially invariant to translation of said multi-channel image;
• transforming rotation and/or scaling in said representation to translation to form a transformed image;
• and
• forming a representation of said transformed image that is substantially invariant to translation of said transformed image, said representation of said transformed image being said matching key for said image.

Apparatus for generating a matching key for an image with said matching key being substantially invariant to rotation, scale and translation, said apparatus comprising:

• means for forming a spatial domain representation of said image that is substantially invariant to translation of said image;
• means for transforming rotation and/or scaling in said spatial domain representation into translation to form a transformed image;
• and
• means for forming a representation of said transformed image that is substantially invariant to translation of said transformed image, said representation of said transformed image being said matching key for said image.

Apparatus for generating a matching key for an image with said matching key being substantially invariant to rotation, scale and translation, said apparatus comprising:

• means for forming a multi-channel image of said image by applying an operator to said image, said operator being commutative within a constant to rotation and scale;
• means for transforming rotation and/or scaling in said representation to translation to form a transformed image;
• means for forming a transformed image from said representation;
• and
• means for forming a representation of said transformed image that is substantially invariant to translation of said transformed image, said representation of said transformed image being said matching key for said image.