Given a color (in [R, G, B] format), Cl = [150, 80, 120], estimate briefly its h

Question

Given a color (in [R, G, B] format), Cl = [150, 80, 120], estimate briefly its hue. Briefly explain how you made such estimation. Given another color, C2 = [75, 40, 60], estimate briefly its hue. Are the two hue values approximately same or exactly same? Explain your method for this comparison. Do Cl and C2 have approximately same or exactly same saturation? Explain your method for this comparison. Are the intensities of Cl and C2 same or different? If they are different, estimate the ratio between the intensities of Cl and C2, and briefly explain your method. Given another color, C3 = [150, 120, 80], estimate its hue. Can you compare the intensities between C3 and Cl? Briefly explain how. The concepts of saturation and intensity are often confused by some people. Briefly explain the difference between the two. Answer the following questions with reference to the following color spectrum without actually computing HSI values using the conversion formula: where the hues for the primary colors are: Red = 0degree Green = 120degree Blue = 240degree

Explanation / Answer

1
Convert the RGB values to the range 0-1, this can be done by dividing the value by 255 for 8-
bit color depth

R = 24 / 255 = 0.09
G = 98 / 255 = 0.38
B = 118 / 255 = 0.46

2
Find the minimum and maximum values of R, G and B.

min = 0.09 (the R value)
max = 0.46 (the B value)

3
Now calculate the Luminace value by adding the max and min values and
divide by 2.

L = (0.09 + 0.46)/2 = 0.275 which rounded up is equal to 28%

4
The next step is to find the Saturation.

If the min and max value are the same, it means that there is no saturation. If all RGB values are equal you have a shade of grey. Depending on how bright it’s somewhere between black and white. If there is no Saturation, we don’t need to calculate the Hue. So we set it to 0 degrees.

But in our case min and max are not equal which means there is Saturation.

5
Now we know that there is Saturation we need to do check the level of the Luminance in order to select the correct formula.
If Luminance is smaller then 0.5, then Saturation = (max-min)/(max+min)
If Luminance is bigger then 0.5. then Saturation = ( max-min)/(2.0-max-min)

In our case Luminance is smaller then 0.5, so we use the first formula.
S = (0.46 – 0.09) / (0.46 + 0.09) = 0.37 / 0.55 = 0.672 which is rounded down equal to 67%

6
Two done, one to go. We still need to calculate the Hue.
The Hue formula is depending on what RGB color channel is the max value. The three different formulas are:
If Red is max, then Hue = (G-B)/(max-min)
If Green is max, then Hue = 2.0 + (B-R)/(max-min)
If Blue is max, then Hue = 4.0 + (R-G)/(max-min)

The Hue value you get needs to be multiplied by 60 to convert it to degrees on the color circle
If Hue becomes negative you need to add 360 to, because a circle has 360 degrees.

Blue is our max, we have to use the third formula.
H = 4.0 + (0.09 – 0.38) / (0.46 – 0.09) = 4.0 + (-0.29)/0.37 = 3.21

Now convert it to degrees
H = 3.21 x 60 = 192.9 which rounded up is 193 degrees

a.326

b.take above example

c.326

d.appro same

e.

g.34

The saturation of a beam of light is related to the width of the plot of intensity vs. wavelength described above. A completely saturated beam would have only one wavelength and would be called monochromatic, which a completely unsaturated beam would contain all wavelengths in equal proportion and would appear white. A completely saturated beam therefore has a very narrow intensity distribution function (possibly consisting of only one non-zero value in the limit), which a completely unsaturated beam has a very wide distribution function, possibly consisting of a constant value over most or all of the visible spectrum

The intensity is related to the strength of the light beam. Intensity is very tricky to specify because the apparent brightness and the actual brightness can differ significantly. Loosely speaking, intensity is related to the total power in the light beam as measured by some objective instrument (such as a photographic light meter), but the perceived brightness of a light (or lightness of a surface) is strongly influenced by lots of other factors and cannot always be specified objectively.

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