Median filtering of images using directed search

A computer-readable medium having instructions stored thereon that when operated on by the computer cause the computer to perform operations comprising:

• determining a first histogram for pixel values within a first window in a first position on an image by sorting pixels of the first window into bins of the first histogram;
• determining a median value of the pixel values using the histogram;
• sliding the first window to a second position on the image to generate a second window where the first window overlaps the second window;
• determining a second histogram of pixel values by modifying the first histogram by extracting a first set of pixels from the first histogram and adding a second set of pixels to the first histogram so that the second histogram has only pixels within the second window;
• determining a second median value of the pixel values using the second histogram by searching pixel values of the second histogram for the median starting at the median value of the first histogram;
• and
• repeating sliding the window determining a histogram and determining a median value until a complete median set of an area of interest of the image is determined.

A computing system comprising:

• a camera to capture an image;
• an image processor apply a median filter to the image by determining a first histogram for pixel values within a first window in a first position on an image by sorting pixels of the first window into bins of the first histogram, determining a median value of the pixel values using the histogram, sliding the first window to a second position on the image to generate a second window where the first window overlaps the second window, determining a second histogram of pixel values by modifying the first histogram by extracting a first set of pixels from the first histogram and adding a second set of pixels to the first histogram so that the second histogram has only pixels within the second window, determining a second median value of the pixel values using the second histogram by searching pixel values of the second histogram for the median starting at the median value of the first histogram, and repeating sliding the window determining a histogram and determining a median value until a complete median set of an area of interest of the image is determined;
• and
• a display to render the median filtered image.