Compositing the frames of a video into a single image can be quite useful in many applications like surveillance and special effects. We propose a novel, and interactive if desired, technique for compositing a video of a scene illuminated part by part by a moving light source into a single image. The automatically composited image provides well illuminated details of the objects in the scene which are in the path of the moving light. The proposed method also recovers the light path along with the illuminant direction and, through the user interaction, allows the user to select any specific sub-path and perform compositing on the corresponding video frames. This approach could prove to be an interesting idea since there is no requirement of camera calibration, modeling of the scene reflectance and light source estimation.

High Dynamic Range (HDR) imaging aims at capturing the entir brightness levels of the real world scene using a single image. This is a challenging probl em which is addressed well in the analog photography which uses films for recording the sce ne information. This is achieved as analog cameras enjoy a much higher dynamic range to record the scene information which amounts to capture of an HDR image. A similar argument is not t rue in the case of digital cameras. The real world brightness differences of scenes with b ot rightly and poorly illuminated regions are so high that the digital sensors are incapable of r c rding all the brightness levels. This is due to the limited storage capacity of the digital sen sors. Common digital cameras with low dynamic range (LDR) sensors lead to overor undersatur ation while capturing an HDR scene. Capturing all the brightness levels of the real world scene u sing a single digital HDR image is a very challenging task. As the problem associated w ith HDR image generation is due to the sensor, one can design a specialized sensor with prope r modifications in order to get an HDR image with a single snapshot. There are indeed HDR sensor s which can capture more brightness levels than that of common digital sensors. The d igital cameras which use these sensors are quite expensive at present. The other option is t develop algorithms for processing images captured using digital cameras with LDR sensors and u se them, in turn, to generate the HDR image of the scene. Traditional algorithmic approaches for HDR imaging requir e one to composite multiple differently exposed images of a scene in the irradiance doma in. The multi-exposure images together have information of all the brightness levels of th e scene which are then reproduced in the generated HDR image. We further have to perform tone ma pping of the generated HDR image for displaying on LDR devices such as common displays a nd printers. In this thesis, we consider algorithmic solutions for the HD R imaging problem. We first develop algorithms for directly generating an LDR image cor responding to a static scene given iii

Illumination compositing for dark scenes

Low Dynamic Range Solutions to the High Dynamic Range Imaging Problem

We propose a technique for fusing a bracketed exposure sequence into a high quality image, without converting to High dynamic range (HDR) first. Skipping the physically based HDR assembly step simplifies the acquisition pipeline. This avoids camera response curve calibration and is computationally efficient. It also allows for including flash images in the sequence. Our technique blends multiple exposures, guided by simple quality measures like saturation and contrast. This is done in a multiresolution fashion to account for the brightness variation in the sequence. The resulting image quality is comparable to existing tone mapping operators.

Illumination compositing for dark scenes

Citations

Low Dynamic Range Solutions to the High Dynamic Range Imaging Problem

References

Exposure Fusion: A Simple and Practical Alternative to High Dynamic Range Photography

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