Abstract
Abstract. 3D laser scanners are typically not able to collect color information. Therefore coloring is often done by projecting photos of an additional camera to the 3D scans. The capturing process is time consuming and therefore prone to changes in the environment. The appearance of the colored point cloud is mainly effected by changes of lighting conditions and corresponding camera settings. In case of panorama images these exposure variations are typically corrected by radiometrical aligning the input images to each other. In this paper we adopt existing methods for panorama optimization in order to correct the coloring of point clouds. Therefore corresponding pixels from overlapping images are selected by using geometrically closest points of the registered 3D scans and their neighboring pixels in the images. The dynamic range of images in raw format allows for correction of large exposure differences. Two experiments demonstrate the abilities of the approach.
Highlights
In the past years some devices have come to market that have an integrated camera, but the resulting color information are sometimes of limited quality
Further image processing steps include a transform to a standardized color space, compression of the dynamic range
The problem of radiometrically aligning a point cloud consisting of several 3D scans is separable in two subproblems
Summary
In the past years some devices have come to market that have an integrated camera, but the resulting color information are sometimes of limited quality. The relation of radiance and its corresponding image point is usually modeled by a vignetting term considering the radial fall off of the lens and the camera response function, which models the non-linear processes within the camera. Both are determined either by precalibration or simultaneously during the alignment of the images. (Eden et al, 2006) compute seamless high dynamic range panoramas by radiometrical aligning the input images They compute white balance gains between radiance maps of overlapping images. These correspondences are radiometrically aligned exploiting the dynamic range of the raw images produced by the camera
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