Activity 11: Color Image Processing

"...All the muse in myself
My desire I can't hide
No reason and I thought..."

White balance on cameras allows one to select white balancing constants appropriate for different capturing conditions. Typical icons found on cameras are sun, cloud, light bulb and a fluorescent lamp. Two popular algorithms for achieving automatic white balance are known: White Patch Algorithm and Gray World Algorithm. White Patch algorithm makes use of the RGB values of a white patch in an image and uses it as a divider. The Gray World Algorithm on the other hand utilizes the average of Red, Green and Blue values of the image and use them as constant dividers.

The following object is a combination of different colors: red, green, yellow hues of red etc.

Auto
(original, White Patch, Grayworld)

The original image is bluish. Application of the white Patch algorithm (where the white patch here is represented by the wall) resulted to a brownish image. Application of Gray World algorithm resulted to a blue-gray image also but it appeared brighter than the original image.

Cloudy
(original, White Patch, Grayworld)

Cloudy image is more of brownish yellow. Application of White Patch algorithm brightened the image and whitened the wall. Gray World algorithm on the other hand made the image appear purple-blue.

Daylight
(original, White Patch, Grayworld)

Image in daylight setting is somewhat similar with the cloudy option only that it is brighter. Application of White Patch algorithm brightened the image and made the wall appear white. Colors in the image appear clearer and more visible than the original image. Application of Gray World Algorithm resulted to a purple-blue image.

Fluorescent
(original, White Patch, Grayworld)

Image under fluorescent setting appeared grayish blue. Application of White Patch Algorithm brightened up the image and made the wall appear close to white. Application of Gray World Algorithm made the image appear blue-gray.

Incandescent
(original, White Patch, Grayworld)

Under incandescent light, orginal object appeared blue. Application of White Patch Algorithm made the image appear whiter. Blue here vanished. The same obervation applies to Gray World Algorithm.

Red (Cloudy)
(original, White Patch, Grayworld)

Objects of similar hues (red plastic bag and red marker) are placed together and photographed under cloudy conditions. It is observed that white patch algorithm did a better job than gray world algorithm in terms of white balancing.

White patch algorithm has the advantage of neutralizing whatever bias is found on the image. Since a white patch found on the object is also exposed under the same light conditions, thus, it serves as a better dividing constant than the average of RGB values.

Rating: 9
I'm unsure of the Grayworld Algorithm results. Nevertheless, i have understood all other concepts.

Reference:
[1] M. Soriano, A11 – Color Image Processing, 2009.