Multiscale gradation processing method

A method of generating a contrast enhanced version of a grey value image by an image processing computer comprising the steps of:

• creating via the image processing computer a multi-scale representation of said image by decomposing a raw digital image, and
• applying via the image processing computer a reconstruction process to said multi-scale representation whereby a scale-specific conversion function is inserted at each successive stage of said reconstruction process from a predefined large scale on so that the output of a stage of said reconstruction process is converted by a conversion function specified for that scale before being supplied to the input of a next stage of the reconstruction process;
• wherein a specification of contrast amplification as a function of grey value at two or more successive scales is defined in advance and the conversion functions for each of said successive scales are derived from said specifications, and wherein the scale-specific conversion function is derived from a series of scale-specific gradient functions that specify the amount of contrast amplification as a function of grey value at successive scales;
• and wherein gradient functions for intermediate scales in between said large scale and a predefined small scale have a shape that evolves gradually from the shape of the gradient function for said large scale to the shape of a gradient function for said predefined small scale, and wherein the gradient function gmk( ) at intermediate scales k are defined by:
• gm
• k
• ⁡
• (
• )
• =
• gm
• S
• ⁡
• (
• )
• ·
• (
• gm
• L
• ⁡
• (
• )
• gm
• S
• ⁡
• (
• )
• )
• k
• -
• S
• L
• -
• S
• where gmL( ) is said large-scale gradient function at scale L, gmS( ) is said small-scale gradient function at scale S, and S<k<L.