Determination of a contrast value for a digital image

A non-transitory computer readable storage medium including instructions which, when executed by a device having a processing capability, cause the device to execute instructions for determining a local contrast value for a digital image captured by an image sensor in a camera, the instructions causing the device to perform operations comprising:

• applying an edge detection algorithm to image data of the digital image, thereby obtaining a data set pertaining to edges in the digital image;
• calculating, based on said data set, an edge occurrence value for the digital image;
• estimating, based on image data of the digital image and a noise model of the image sensor, image sensor noise for the digital image;
• estimating, based on the estimated image sensor noise, an expected value of edge occurrence;
• and
• computing the local contrast value as a relationship between the edge occurrence value of the digital image and the estimated expected value of edge occurrence.

A circuitry configured to determine a local contrast value for a digital image captured by an image sensor in a camera, the circuitry comprising:

• a memory configured to store image data of the digital image;
• and
• a circuitry configured to:
• apply an edge detection algorithm to image data of the digital image, thereby obtaining a data set pertaining to edges in the digital image;
• based on said data set, calculate an edge occurrence value for the digital image;
• based on image data of the digital image and a noise model of the image sensor, estimate a value of image sensor noise for the digital image, and, based on the estimated image sensor noise for the digital image, estimate an expected edge occurrence value;
• and
• compute the local contrast value as a relationship between the edge occurrence value of the digital image and the estimated expected value of edge occurrence.

A focus adjustable digital camera, the camera comprising:

• a memory configured to store image data pertaining to a series of images captured by the camera, each image of the image series being captured using a different focus setting of the camera;
• a circuitry configured to determine a local contrast value of each image of the series of images, the circuitry comprising:
• a memory configured to store image data of the digital image;
• and
• a circuitary to:
• apply an edge detection algorithm to image data of the digital image, thereby obtaining a data set pertaining to edges in the digital image;
• based on said data set, calculate an edge occurrence value for the digital image;
• based on image data of the digital image and a noise model of the image sensor, estimate a value of image sensor noise for the digital image, and, based on the estimated image sensor noise for the digital image, estimate an expected edge occurrence value;
• and
• compute the local contrast value as a relationship between the edge occurrence value of the digital image and the estimated expected value of edge occurrence.
• a processor configured to:
• compare the local contrast values for the images of the series of images;
• and
• select a focus setting of the digital camera based on the comparison;
• and
• a controller configured to adjust the focus setting of the digital camera based on the selected focus setting.