Defogging images and video

Patent metadata

Field	Value
Publication number	US-2016155218-A1
Application number	US-201414555803-A
Country	US
Kind code	A1
Filing date	Nov 28, 2014
Priority date	Nov 28, 2014
Publication date	Jun 2, 2016
Grant date	—

Abstract

A method and system are disclosed. The method may include determining a histogram of intensity values for pixels in image sensor data in which the histogram is bimodal. The method may include determining a breakpoint between the two modes. The histogram may include a first distribution of intensity values below the breakpoint and a second distribution of intensity values above the breakpoint. The method may include generating output intensity values. Generating output intensity values may include compressing the first distribution of intensity values of the pixels with intensity values below the breakpoint, stretching the second distribution of intensity values of the pixels with intensity values above the breakpoint, and generating an output image based on the output intensity values.

First claim

What is claimed is:

1 . A method comprising:
determining a histogram of intensity values for pixels in image sensor data, wherein the histogram is bimodal; determining a breakpoint between the two modes, wherein the histogram includes a first distribution of intensity values below the breakpoint and a second distribution of intensity values above the breakpoint; and generating output intensity values by:
compressing the first distribution of intensity values of the pixels with intensity values below the breakpoint,
stretching the second distribution of intensity values of the pixels with intensity values above the breakpoint, and
generating an output image based on the output intensity values.

2 . The method of claim 1 , wherein the image is a current image in a video stream, wherein the video stream includes a previous image in the video stream, the method further comprising:
determining a previous histogram of intensity values for pixels in the previous image, wherein the previous histogram is bimodal; determining a previous breakpoint between the two modes of the previous histogram; and determining the breakpoint for the current image based on the previous breakpoint.

3 . The method of claim 2 ,
wherein the video stream includes a plurality of previous images, and wherein the breakpoint for the current image is determined based on a plurality of previous breakpoints between modes in the corresponding plurality of previous images.

4 . The method of claim 3 , wherein determining the current breakpoint includes applying a low-pass filter to the plurality of previous breakpoints.

5 . The method of claim 3 , further comprising:
generating an output video stream based on the output intensity values; compressing the output video stream to generate a compressed video stream; and transmitting the compressed video stream to a monitoring station.

6 . The method of claim 1 , further comprising:
determining if the histogram is bimodal.

7 . The method of claim 6 , wherein determining if the histogram is bimodal includes determining if the histogram includes two local maxima.

8 . The method of claim 6 , wherein determining if the histogram is bimodal includes determining if the pixel intensities are clustered around two separated values.

9 . The method of claim 1 , wherein stretching the second distribution of intensity values includes stretching the second distribution of intensity values to include intensity values below the breakpoint.

10 . The method of claim 9 , wherein a user-defined parameter determines an extent to which stretching the second distribution of intensity values includes intensity values below the breakpoint.

11 . A device comprising:
a camera to capture an image and generate image sensor data; and a processor to
determine a histogram of intensity values for pixels in the image sensor data, wherein the histogram is bimodal;
determine a breakpoint between the two modes, wherein the histogram includes a first distribution of intensity values below the breakpoint and a second distribution of intensity values above the breakpoint;
generate output intensity values by
compressing the first distribution of intensity values of the pixels with intensity values below the breakpoint, and
stretching the second distribution of intensity values of the pixels with intensity values above the breakpoint; and

generate an output image based on the output intensity values.

12 . The device of claim 10 , wherein the image is a current image in a video stream, wherein the video stream includes a previous image, and wherein the processor is further configured to:
determine a previous histogram of intensity values for pixels in the previous image, wherein the previous histogram is bimodal; determine a previous breakpoint between the two modes of the previous histogram; and determine the breakpoint for the current image based on the previous breakpoint.

13 . The device of claim 12 ,
wherein the video stream includes a plurality of previous images, and wherein, when determining the breakpoint for the current image, the processor is further configured to determine the breakpoint of the current image based on a plurality of previous breakpoints between modes in the corresponding plurality of previous images.

14 . The device of claim 13 , wherein the processor is configured to determine the current breakpoint by applying low-pass filter logic to the plurality of previous breakpoints.

15 . The device of claim 13 , wherein the processor is further configured to:
generate an output video stream based on the output intensity values; and compress the output video stream to generate a compressed video stream, wherein the device further includes a transmitter to send the compressed video stream across a network to a monitoring station.

16 . The device of claim 11 , wherein the processor is further configured to determine if the histogram is bimodal.

17 . The device of claim 16 , wherein when the processor determines if the histogram is bimodal, the processor is further configured to determine if the histogram includes two local maxima.

18 . The device of claim 16 , wherein when the processor determines if the histogram is bimodal, the processor is further configured to determine if pixel intensities are clustered around two separated values.

19 . The device of claim 11 , wherein the processor is configured to stretch the second distribution of intensity values to include intensity values below the breakpoint.

20 . The device of claim 19 , wherein the processor is configured to stretch the second distribution of intensity values to include intensity values below the breakpoint to an extent based on a user-defined parameter.

Assignees

• Axis Ab

Inventors

• Svensson Fredrik
• Kannermark Per
• Nilsson Andreas

Classifications

• G06T5/20

  using local operators · CPC title

• G06T5/40

  using histogram techniques · CPC title

• G06T2207/20208

  High dynamic range [HDR] image processing · CPC title

• G06T5/009 Primary

  Physics · mapped topic

• H04N7/183

  for receiving images from a single remote source · CPC title