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86 2 Image formation

Ex 2.10: In-camera color processing—challenging If your camera supports a RAW pixel
mode, take a pair of RAW and JPEG images, and see if you can infer what the camera is doing
when it converts the RAW pixel values to the final color-corrected and gamma-compressed
eight-bit JPEG pixel values.

1. Deduce the pattern in your color filter array from the correspondence between co-
located RAW and color-mapped pixel values. Use a color checker chart at this stage
if it makes your life easier. You may find it helpful to split the RAW image into four
separate images (subsampling even and odd columns and rows) and to treat each of
these new images as a “virtual” sensor.

2. Evaluate the quality of the demosaicing algorithm by taking pictures of challenging
scenes which contain strong color edges (such as those shown in in Section 10.3.1).
3. If you can take the same exact picture after changing the color balance values in your
camera, compare how these settings affect this processing.
4. Compare your results against those presented by Chakrabarti, Scharstein, and Zickler
(2009) or use the data available in their database of color images. 26

26 http://vision.middlebury.edu/color/.