Digital Image Processing: Color Fundamentals

Processing of images containing color information.

The properties of colors and how the human eye perceives them.

Sunlight split into a spectrum of colors through a prism.

Visible light spans the electromagnetic spectrum (400-700 nm).

Objects appear colored due to the reflected light they emit.

Ways of representing colors numerically.

The full range of electromagnetic radiation in the universe.

Visible light waves range from 400-700 nanometers.

Red, green, and blue light that are mixed to create other colors.

Colors that are mixed together to create other colors. Unlike light, mixing them doesn't produce white.

Colors that are made by mixing two primary colors together.

The intensity or lightness/darkness of a color, not dependent on the color itself.

The dominant wavelength of a color.

Mixing a secondary color with its opposite primary color of a light creates white.

Distinguishing one color from another.

Mixing the primary colors of light creates white (not pigments).

Human color vision depends on approximately 6 to 7 million cones in each eye that absorb light at different wavelengths.

Objects reflect light, primarily in a specific wavelength range, and absorb the rest of the light spectrum.

The total amount of energy from a light source measured in watts.

The perceived amount of energy from a light source measured in lumens.

Cone cells in the eye are sensitive to red, green, and blue light; different proportions make color.

The percentage of cones that respond to colors (red, green, and blue) differ.

Cone sensitivity findings do not exactly match the earlier CIE color standards measured in nanometers.

A diagram used to represent colors and their mixing ratios.

The purity of a color, measured on the boundary of the chromaticity chart.

A standard color with equal amounts of red, green, and blue.

Mixing colors by combining their light sources.

Represents fully saturated (pure) colors.

A line in the diagram connecting two colors, showing all mixtures of those colors.

Combining any three colors results in colors inside the triangle their ratios.

The color defined by given ratios of the colors in the chart

A color model based on combining red, green, and blue light to produce a wide range of colors. Each color component is represented as a value between 0 and 255.

A way to represent a color in the RGB model using six hexadecimal digits, where each pair of digits represents the intensity of red, green, or blue (e.g., #FF0000 is red).

A subtractive color model based on cyan, magenta, and yellow pigments. Combining all three pigments should theoretically produce black, but in practice it results in a muddy color.

An extension of the CMY model that adds black (K) as a fourth color to provide a true black for printing purposes.

A color model where mixing colors involves subtracting light from white light by absorbing specific wavelengths. This is the model used for pigments like paints.

A color model where mixing colors involves adding light. This is the model used for light sources like TV screens.

A color model that represents colors based on Hue, Saturation, and Intensity (Brightness). It offers a more intuitive way to represent colors compared to RGB or CMYK.

The saturation of a color in the HSI color model represents the percentage of white missing from the color. Higher saturation indicates less white and a more intense color.

In the HSI color model, hue represents the pure color itself, independent of brightness or saturation. It's described by an angle around the intensity axis.

To extract hue from the RGB color cube, consider a plane defined by cyan, black, and white. All points within this plane share the same hue (cyan).

The RGB color space is represented by a cube with each corner representing a primary color (red, green, blue). Each point inside the cube corresponds to a unique color.

The HSI values can be calculated from the RGB values. This involves converting the RGB color information into the HSI color space.

When viewed from above, the HSI color space appears as a hexagon with primary colors separated by 120 degrees and secondary colors at 60 degrees from the primaries.

The HSI and RGB color models are both ways to represent color, but they differ in the way they handle the color information. HSI is more intuitive for human understanding, while RGB is used in computers.