24 Questions
What is the outcome when you add portions of red, green, and blue in the RGB color model?
White
What is the principle of the CMYK color model?
Subtractive color
When is it best to use the RGB color model?
When displaying on a computer monitor
What does HSL stand for in the HSL color model?
Hue, Saturation, Lightness
What does a saturation value of 0 indicate?
A color with mostly grey
What is the range of the hue value in the HSL color model?
0 to 360
What is the effect of increasing the saturation value in the HSL color model?
The color becomes more intense
What is the difference between HSL and HSV color models?
A color with maximum lightness in HSL is pure white, but a color with maximum value/brightness in HSV is analogous to shining a white light on a colored object
What does the 'L' component in the LAB color model represent?
Luminosity from black to white
What is the purpose of the lightness value in the HSL color model?
To adjust the brightness of the color
What is the purpose of the YUV color model?
To separate brightness and color information, especially for video
What is the alternative color model to HSL?
HSV
What is the formula for deriving Luma (Y) in the YUV color model?
Y = 0.2125R + 0.7145G + 0.0721B
What are the three values that represent any color in the YUV color model?
Y, U, and V
What does the 'B' component in the LAB color model represent?
Blue from -128 to +127
What is the advantage of the HSL and HSV color models?
They are more closely aligned with the way human vision perceives color-making attributes
What is the basis of color reproduction in monitors?
Standard red, green and blue as primaries
What is the purpose of using indexed color?
To reduce the size of image without using lossy compression
How many colors can be represented by an 8-bit color component?
256 colors
What is the term used to describe 216 colors that are guaranteed to reproduce accurately on all platforms and browsers?
Web-safe palette
How do TVs and computer monitors produce colors?
By using optical mixing of red, green, and blue light
What is the minimum number of bits required to represent 256 grays in an image?
8 bits
What is the term used to describe the number of bits used to represent each color component?
Color depth
What is the advantage of using a 24-bit color representation?
It can represent millions of colors
Study Notes
RGB Color Model
- Also known as "additive color"
- Colors are added together to achieve further colors, with the outcome being white
- Our eyes receive no reflected light, perceiving black when no colors are added
CMYK Color Model
- Subtractive color model
- Starts with all colors and subtracts to achieve white
- Colors absorb light
When to Use RGB vs CMYK
- Use RGB for computer monitor output
- Use CMYK for printed materials
HSL Color Model
- Supported in modern browsers
- Stands for Hue, Saturation, and Lightness
- Hue is a degree on the color wheel (0-360)
- Saturation is the intensity of a color (0-100%)
- Lightness is how much light is given to the color (0-100%)
HSV Color Model
- Alternative way of specifying color
- Hue is the actual color (0-360)
- Saturation indicates the amount of grey in a color (0-100%)
- Value (brightness) refers to how much white or black is mixed in the color
HSL vs HSV
- HSL: maximum lightness is pure white
- HSV: maximum value/brightness is shining a white light on a colored object
LAB or CIE Color Model
- L: lightness from black (0) to white (100)
- A: from green (-128) to red (+127)
- B: from blue (-128) to yellow (+127)
YUV Color Model
- Defines a color space in terms of one Luma (Y) and two chrominance (UV) components
- Can separate brightness and color information
- Luma is derived from an RGB color by taking a weighted average of the red, green, and blue components
Color
- A particular color is defined by the proportions of red, green, and blue light it contains
- TVs and computer monitors use pixels made up of three dots of different types of phosphor, emitting red, green, and blue light
RGB Color Storage
- Represent any color with three numbers (r, g, b)
- Use as pixel's stored value in bitmapped image
- Can choose number of bits for each of r, g, and b
- More bits per component means more colors can be distinguished, but image files will be larger
Color Depth
- 8 bits (1 byte) per component -> 256 colors
- 24-bit -> millions of colors
- If r = g = b, color is a shade of grey
Indexed Color
- 8-bit color only permits 256 colors
- Instead of storing (r, g, b) for each pixel, store an index into a palette or Color Lookup Table (CLUT)
- Index can be small, usually a single byte
Understand the difference between RGB and CMYK color models, also known as additive and subtractive color models, and how they work.
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