Allan Didier

Computer Science Teacher

# Digitizing Color

How does the computer generate color from only 1’s and 0’s?  How is color digitized?

#### What Is Color?

• Your eye detects certain frequencies of the electromagnetic spectrum
• Different frequencies are seen as different colors.
• Your eye only detects red, green, and blue colors. The other colors are made from a mix of these 3 colors.

#### What are the Primary Colors of Light?

• Primary colors: RGB: red, green, and blue
• Yellow = red + green
• Cyan = green + blue
• Magenta = red + blue
• Use the Physics Simulation RGB light mixer to see the color interaction.

#### What are the Primary Colors of Pigment?

• Primary colors for computer pigment: CMYK
• C = Cyan (light blue)
• M = Magenta (pinkish red)
• Y = Yellow
• K = Black (B = Blue)
• Cyan + Magenta = Blue
• Magenta + Yellow  = Red
• Cyan + Yellow = Green
• Use the Physics Simulation CMY paint mixer to see he color interaction.

#### How is Color Digitized?

• Light
• Amount of each color is a binary number often in hex for humans.
• Color = Red# + Green# + Blue#
• 24 bit color (standard color scheme)
• 3 colors (RGB)
• 2 hex numbers per color (1 byte per color = 8 bits)
• 3 colors * 8 bits = 24 bit color
• Red = ff 00 00
• Green = 00 ff 00
• Blue = 00 00 ff
• Yellow = Red + Green = ff ff 00
• Cyan = Green + Blue = 00 ff ff
• Magenta = Red + Blue = ff 00 ff
• What color number is white?
• What color number is black
• What color number is orange?
• Use google docs color mixer to see this.
• Pigment
• Similar to above but using CMYK instead of RGB.
• Cyan = ff 00 00 00