Image processing device and image processing method

1. An image processing device configured to be installed in a vehicle, comprising:

an image acquirer configured to acquire camera images captured by cameras provided on the vehicle;

an image selector configured to calculate, for each of the camera images, an average value of luminances of respective pixels constituting each of the camera images, and to select one of the camera images having a highest average value as a representative image;

a first luminance adjuster configured to adjust a luminance of at least one of the other camera images based on a luminance of the representative image;

a synthetic image generator configured to generate a synthetic image showing a periphery of the vehicle, based on the representative image and the other camera images the luminance of at least one of which has been adjusted by the first adjuster; and

an image provider configured to output, to a display device installed in the vehicle, information corresponding to the synthetic image.

2. The image processing device according to claim 1 , wherein:

the image selector is configured to exclude the pixels having a luminance no less than a prescribed value when the average value is calculated.

3. The image processing device according to claim 2 , further comprising:

a controller configured to activate the first luminance adjuster when a difference between the highest average value and a lowest average value which are calculated by the image selector is no less than a prescribed value.

4. The image processing device according to claim 3 , further comprising:

a second luminance adjuster configured to adjust a luminance of each of the camera images based on the average value thereof calculated by the image selector, wherein:

the controller is configured to activate the second luminance adjuster when the difference is less than the prescribed value.

5. An image processing method, comprising:

acquiring camera images captured by cameras provided on a vehicle;

calculating, for each of the camera images, an average value of luminances of respective pixels constituting each of the camera images;

selecting one of the camera images having a highest average value as a representative image;

adjusting a luminance of at least one of the other camera images based on a luminance of the representative image;

generating a synthetic image showing a periphery of the vehicle, based on the representative image and the other camera images the luminance of at least one of which has been adjusted; and

outputting, to a display device installed in the vehicle, information corresponding to the synthetic image.

6. An image processing device configured to be installed in a vehicle, comprising:

an image acquirer configured to acquire a camera image captured by a camera provided on the vehicle;

a first average calculator configured to divide the camera image into a plurality of regions each of which includes a plurality of pixels, and to calculate, for each of the regions, an average value of luminances of the respective pixels as a first average value;

a region selector configured to select at least one of the regions in which the first average value is no greater than a threshold value;

a luminance adjuster configured to adjust an entire luminance of the camera image based on the luminance of the at least one of the regions selected by the region selector;

an image provider configured to output, to a display device installed in the vehicle, information corresponding to the camera image the entire luminance of which has been adjusted by the luminance adjuster;

a second average calculator configured to calculate an average value of luminances of the pixels included in the at least one of the regions selected by the region selector, as a second average value; and

a threshold updater configured to update the threshold value based on the second average value.

7. The image processing device according to claim 6 , wherein:

the luminance adjuster is configured to adjust the entire luminance of the camera image based on the second average value.

8. The image processing device according to claim 6 , wherein:

the luminance adjuster is configured to adjust the entire luminance of the camera image based on a highest value of the luminances of the pixels included in the at least one of the regions selected by the region selector.

9. The image processing device according to claim 6 , wherein:

the image acquirer configured to acquire camera images captured by cameras provided on the vehicle;

the first average calculator is configured to calculate the first average value for each of the camera images;

the region selector is configured to select the at least one of the regions for each of the camera images;

the luminance adjuster is configured to adjust the entire luminance for each of the camera images; and

the image processing device further comprises a synthetic image generator configured to generate a synthetic image showing a periphery of the vehicle based on the camera images the entire luminances of which have been adjusted by the luminance adjuster; and

the image provider is configured to output information corresponding to the synthetic image to the display device.

10. An image processing method, comprising:

acquiring a camera image captured by a camera provided on the vehicle;

dividing the camera image into a plurality of regions each of which includes a plurality of pixels;

calculating, for each of the regions, an average value of luminances of the respective pixels as a first average value;

selecting at least one of the regions in which the first average value is no greater than a threshold value;

adjusting entire luminance of the camera image based on the luminance of the at least one of the regions selected;

outputting, to a display device installed in the vehicle, information corresponding to the camera image the entire luminance of which has been adjusted;

calculating an average value of luminances of pixels included in the at least one of the regions selected; and

updating the threshold value based on the second average value.