A15 - Color Camera Processing

In photography and image processing, color balance is the global adjustment of the intensities of the colors (typically red, green, and blue). An important goal of this adjustment is to render specific colors – particularly neutral colors – correctly; hence, the general method is sometimes called gray balance, neutral balance, or white balance. Color balance changes the overall mixture of colors in an image and is used for color correction; generalized versions of color balance are used to get colors other than neutrals to also appear correct or pleasing.

Digital cameras come with white balance (WB) settings. Here are the some white balance settings available in digital cameras:

Daylight - used when taking photos outdoors
Incandescent - used when taking photos under a incandescent bulb
Flourescent - used when taking photos under a flourescent bulb
Sunset - used when taking photos during sunset
Cloudy - used when taking photos during cloudy days

When you set the right WB settings in your camera, then you can remove unrealistic color casts, so that objects which appear white in person are rendered white in your photo.

In this activity, I captured images under the wrong WB settings and try to correct it using scilab.
The process includes taking the RGB value of the white part of the image and divide the entire image with this RGB value.
I used the following codes to treat the images:

stacksize(20000000);
im = imread("leaves.jpg");
im1 = imread("leaves1.jpg");
//Reference white
Rw = mean(im1(:,:,1));
Gw = mean(im1(:,:,2));
Bw = mean(im1(:,:,3));
//Getting the RGB values of the image
R = im(:,:,1);
G = im(:,:,2);
B = im(:,:,3);
//Treating the image
new = zeros(im);
new(:,:,1) = R./Rw;
new(:,:,2) = G./Gw;
new(:,:,3) = B./Bw;
//Writing the new image
maxa = max(max(max(new)));
imnew = new./maxa;
imwrite(imnew,"newleaf.jpg");
//Gray World
Rwg = mean(im(:,:,1));
Gwg = mean(im(:,:,2));
Bwg = mean(im(:,:,3));
newg = zeros(im);
newg(:,:,1) = im(:,:,1)./Rwg;
newg(:,:,2) = im(:,:,2)./Gwg;
newg(:,:,3) = im(:,:,3)./Bwg;
maxb = max(max(max(newg)));
imnewg = newg./maxb;
imwrite(imnewg,"newgleaf.jpg");

And here are the results:
Figure 1. Photo taken under incandescent setting but should be taken under flourescent setting.

Figure 2. Treated Image of Figure 1 (White Balanced)
Figure 3. Treated Image of Figure 1 (Gray Balanced)

The other treated image appears below.

Figure 4. Photo of leaves taken under broad daylight.(L-R) The setting used was incandescent. White balanced image of the leaves. Gray balanced image of the leaves.

Figure 5. Photo of objects taken under broad daylight.(L-R) The setting used was incandescent. White balanced image of the leaves. Gray balanced image of the leaves.

References:
en.wikipedia.org/wiki/White_balance
www.cambridgeincolour.com/tutorials/white-balance.htm