Multiresolution method of spatially filtering a digital image

Apparatus for processing a digital image to improve tone scale, comprising:

• a) means for generating a multiresolution image representation of an original digital image including a plurality of base digital images and a plurality of residual digital images wherein:
• i) the base digital images are each of a different spatial resolution and are lower spatial resolution versions of the original digital image;
• ii) the residual digital images have different spatial resolution and include spatial detail relating to a different pass-band of spatial frequencies;
• b) means for applying a texture reducing spatial filter to the base digital images to produce texture reduced base digital images;
• and
• c) means for combining the texture reduced base digital images and the residual digital images to generate a texture reduced digital image;
• d) means for subtracting the texture reduced digital image from the original digital image to produce a texture digital image;
• e) means for applying a compressive tone scale function to the texture reduced digital image to produce a tone scale adjusted digital image having a compressed tone scale in at least a portion of the image;
• and
• f) means for combining the texture digital image with the tone scale adjusted digital image to produce an enhanced digital image, whereby the contrast of the enhanced digital image is improved without compressing the contrast of the texture in the original digital image.

A method of processing a digital image to improve tone scale, comprising the steps of:

• a) generating a multiresolution image representation of the original digital image including a plurality of base digital images and a plurality of residual digital images wherein:
• i) the base digital images are each of a different spatial resolution and are lower spatial resolution versions of the original digital image;
• ii) the residual digital images have different spatial resolution and include spatial detail relating to a different pass-band of spatial frequencies;
• b) applying a texture reducing spatial filter to the base digital images to produce texture reduced base digital images;
• and
• c) combining the texture reduced base digital images and the residual digital images s to generate a texture reduced digital image;
• d) subtracting the texture reduced digital image from the original digital image to produce a texture digital image;
• e) using the original digital image to generate a tone scale function and applying the tone scale function to the texture reduced digital image to produce a tone scale adjusted digital image;
• and
• f) combining the texture digital image with the tone scale adjusted digital image to produce an enhanced digital image, whereby the contrast of the enhanced digital image is improved without compressing the contrast of the texture in the original digital image.

Apparatus for processing a digital image to improve tone scale, comprising:

• a) means for generating a multiresolution image representation of an original digital image including a plurality of base digital images and a plurality of residual digital images wherein:
• i) the base digital images are each of a different spatial resolution and are lower spatial resolution versions of the original digital image;
• ii) the residual digital images have different spatial resolution and include spatial detail relating to a different pass-band of spatial frequencies;
• b) means for applying a texture reducing spatial filter to the base digital images to produce texture reduced base digital images;
• and
• c) means for combining the texture reduced base digital images and the residual digital images to generate a texture reduced digital image;
• d) means for subtracting the texture reduced digital image from the original digital image to produce a texture digital image;
• e) means for generating the tone scale function using the original digital image and means for applying the tone scale function to the texture reduced digital image to produce a tone scale adjusted digital image;
• and
• f) means for combining the texture digital image with the tone scale adjusted digital image to produce an enhanced digital image, whereby the contrast of the enhanced digital image is improved without compressing the contrast of the texture in the original digital image.

A method of reducing the dynamic range of an input digital image for effectively rendering the input digital image on an output display medium, the method comprising the steps of:

• a) extracting residual digital images and base digital images from an input digital image;
• b) generating mask signals from the input digital image by detecting base digital image edges;
• c) modifying the base digital images according to the mask signals;
• and
• d) adding the modified base digital images and the residual digital images to obtain an output digital image.