In Digital Image Processing, what is the difference between the intensity and the saturation of a color?
How would you explain the difference to a newbie?
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When you take an RGB Image matrix and convert the color into HSV Color Model the color is represented on Cylinder.
Now, the intensity (Lightness / Value) is the height on this Cylinder which is going from black to white and basically sets the Gray Color of the neutral color (One which blends RGB in the same intensity).
Saturation is the Radius and intuitively is how far the color is from being neutral (Pure Gray).
Namely, how dominant is one color component versus the others.
For 24-bit RGB colors: R=1,G=0,B=0 would be maximally saturated (100%) red, but at the lowest intensity. R=255,G=254,B=254 would be very high intensity, but very low saturation (most people wouldn't even notice the slight red-ness of the near white).
Saturation is usually one property of three when used to determine a certain color and measured as percentage value.
Saturation defines a range from pure color (100%) to gray (0%) at a constant lightness level. A pure color is fully saturated.
From a perceptional point of view saturation influences the grade of purity or vividness of a color/image. A desaturated image is said to be dull, less colorful or washed out but can also make the impression of being softer.
In general, intensity is a synonym for magnitude, degree or strength. It can therefore be used in conjunction with any color property. Nevertheless, it carries special meaning in certain contexts.
The intensity refers to different aspects of radiation.
When speaking of light, the intensity can mean the number of photons a light source emits.
The following sources provide a deeper insight:
Luma (%) is the intensity of the achromatic signal contributing to our color perception.
Where did you get the term 'colour intensity'?
If by that you mean 'colourfulness' as distinct from saturation, this might be of help:
" Colourfulness is the “attribute of a visual perception according to which the perceived colour of an area appears to be more or less chromatic” (17-233). Saturation is the “colourfulness of an area judged in proportion to its brightness” (17-1136). Chroma is the “colourfulness of an area judged as a proportion of the brightness of a similarly illuminated area that appears white or highly transmitting” (17-139). "