Per-pixel photometric contrast enhancement with noise control
AssigneeApple Inc.
InventorMaxim Smirnov
Life of this patent
Estimating the term…
Abstract
Embodiments relate to enhancing local contrast in an image. A bilateral high pass filter generates a high frequency value for each pixel of an input image, based on a convolution using photometric kernel coefficients associated with other pixels around the pixel. A noise control circuit generates a modulated high frequency value for the pixel based on a noise model for the image defining a noise threshold value for modifying the high frequency value. The modulated high frequency value for the pixel is then combined with a pixel value of the pixel to generate an enhanced value for the pixel. Enhanced values for pixels of the image may be generated to provide the local contrast enhancement for the input image.
Claims20
An apparatus for enhancing an image, comprising:
- a bilateral high pass filter configured to generate a high frequency value for a pixel of the image based on a convolution using photometric kernel coefficients associated with other pixels around the pixel;
- a noise control circuit coupled to the bilateral high pass filter, the noise control circuit configured to generate a modulated high frequency value for the pixel based on a noise model for the image defining a noise threshold value for modifying the high frequency value;
- and
- a combiner coupled to the noise control circuit, the combiner configured to generate an enhanced value for the pixel by combining the modulated high frequency value for the pixel with a pixel value of the pixel.
A method for enhancing an image, comprising:
- generating a high frequency value for a pixel of the image based on a convolution using photometric kernel coefficients associated with other pixels around the pixel;
- generating a modulated high frequency value for the pixel based on a noise model for the image defining a noise threshold value for modifying the high frequency value;
- and
- generating an enhanced value for the pixel by combining the modulated high frequency value for the pixel with a pixel value of the pixel.
A system, comprising:
- an image sensor configured to obtain an image having a plurality of color components;
- an image signal processor coupled to the image sensor, the image signal processor configured to perform de-noising of the image to obtain a de-noised version of the image having one or more color components of the plurality of color components, the image signal processor including:
- a bilateral high pass filter configured to generate a high frequency value for a pixel of the de-noised version of the image based on a convolution using photometric kernel coefficients associated with other pixels around the pixel,
- a noise control circuit coupled to the bilateral high pass filter, the noise control circuit configured to generate a modulated high frequency value for the pixel based on a noise model for the image defining a noise threshold value for modifying the frequency value, and
- a combiner coupled to the noise control circuit, the combiner configured to generate an enhanced value for the pixel by combining the modulated high frequency value for the pixel with a pixel value of the pixel.
Dependencies are inferred from the claim text.