Method and apparatus for glare detection

1. A glare detection method for detection of at least one glare region within an image, said method comprising:

aggregating image pixels of the image having a high luminance intensity into bright image areas within the image, the high luminance intensity being an intensity above a predetermined threshold;

calculating for image pixels around each bright image area gradient directions expected in case of a glare and actual gradient directions;

increasing a glare diameter of a glare region around the respective bright image area as long as the calculated actual gradients match the calculated expected gradients;

computing similarity metrics between the calculated actual gradient directions and the calculated expected gradient directions; and

computing an average similarity value of the computed similarity values for image pixels being located in a neighboring image area around the respective bright image area and being equidistant to the respective bright image area;

wherein the average similarity value is calculated with a stepwise increased distance between the equidistant image pixels of the neighboring image area and the respective bright image area until the respective calculated average similarity value becomes smaller than a predetermined threshold value, and wherein the equidistant image pixels of the last incrementing step define the outer boundary of the glare region within the image.

2. The glare detection method according to claim 1 wherein the image is part of an image sequence of images provided by a camera.

3. The glare detection method according to claim 2 wherein a glare is detected if a glare region is detected around a bright image area for a predetermined number N of images in the image sequence provided by the camera.

4. The glare detection method according to claim 2 wherein the image is generated by a camera of a vehicle.

5. The glare detection method according to claim 2 wherein the image provided by the camera is a digital image comprising a plurality of pixels each having a luminance intensity.

6. The glare detection method according to claim 1 wherein the image is downscaled and the downscaled image is scanned for image pixels having a high luminance intensity above a predetermined luminance intensity threshold.

7. The glare detection method according to claim 6 wherein the image pixels of the downscaled image having a high luminance intensity above the predetermined luminance intensity threshold are aggregated into connected areas labelled as bright image areas of the image.

8. A glare detection apparatus for detection of at least one glare region within an image, said apparatus comprising:

a processing unit configured to aggregate image pixels of the image having a high luminance intensity to bright image areas within the image, the high luminance intensity being an intensity above a predetermined threshold, and to calculate for image pixels around each bright image area gradient directions expected in case of a glare and actual gradient directions and configured to increase a glare diameter of a glare region around the respective bright image area as long as the calculated actual gradient directions match the calculated expected gradient directions;

wherein said processing unit is further configured to compute similarity metrics between the calculated actual gradient directions and the calculated expected gradient directions and is configured to calculate an average similarity value of the computed similarity values for image pixels being located in a neighboring image area around the respective bright image area and being equidistant to the respective bright image area;

wherein said processing unit is configured to calculate an average similarity value with a stepwise increased distance between the equidistant image pixels of the neighboring image area and the respective bright image area until the respective calculated average similarity value becomes smaller than a predetermined threshold value; and

wherein the equidistant image pixels of the last incrementing step define the outer boundary of the glare region within the image.

9. The glare detection apparatus according to claim 8 wherein said apparatus further comprises a downscaling unit adapted to downscale the image,

wherein said downscaled image is scanned by the processing unit for image pixels having a high luminance intensity above a predetermined luminance intensity threshold,

wherein image pixels of the downscaled image having a high luminance intensity above the predetermined luminance intensity are aggregated by the processing unit into connected areas labelled as bright image areas of the image.