How to Study Colors
Interpolation in colors is the process of generating a smooth sequence of colors between a starting color and an ending color. It is widely used in computer graphics, image processing, and data visualization to create gradients and smooth transitions.
The fundamental idea is to move along a path within a chosen color space (like RGB, HSL, or LAB) by calculating weighted averages of the start and end color components.
Common Algorithms and Calculation Steps
The choice of algorithm depends heavily on the color space used for interpolation. Different spaces yield different visual results.
1. Linear Interpolation in RGB Color Space
Linear interpolation (LERP) in the Red, Green, Blue (RGB) color space is the most straightforward and computationally inexpensive method. It blends the individual R, G, and B components directly.
2. Interpolation in Perceptual Color Spaces (e.g., HSL, HSV, LAB)
While RGB LERP is fast, it often produces gradients that appear dull or have abrupt changes in perceived brightness to the human eye because RGB space is not perceptually uniform. Perceptual spaces like LAB or HSL/HSV are often preferred for visually smooth transitions.
Lab* Interpolation
The CIELAB (Lab)* color space is designed to be perceptually uniform, meaning a linear change in a component corresponds to a roughly linear change in human perception.
HSL/HSV Interpolation (Hue, Saturation, Lightness/Value)
HSL and HSV are often used when the user wants to interpolate along a color wheel path.
Algorithm Steps:
Define Start and End Colors: Represent the colors as component values (e.g., C1 = {R1, G1, B1} and C2 = {R2,B2,C2});
Define Interpolation Parameter: Choose a parameter 't' that ranges from 0.0 to 1.0.
- t = 0.0 gives the starting-color;
- t = 1.0 gives the ending-color, and;
- t = 0.5 gives the midpoint-color.
Apply LERP Formula: Calculate the new color Cnew = (Rnew,Gnew,Bnew) using the following equation for each channel:
Cnew = C1 * (1-t) + C2 * t
Start Color (C1): Red (255, 0, 0)
End Color (C2): Blue (0, 0, 255)
Factor (t): 0.5 (50% blend)
Red: (1 - 0.5) * 255 + 0.5*0 = 127.5
Green: (1 - 0.5) * 0+ 0.5*0 = 0
Blue: (1 - 0.5) * 0+ 0.5*255 = 127.5
Result: (127.5,0,127.5) ≈ (128,0,128) {Purple}
The resulting midpoint color is (128, 0, 128), which is a shade of purple.
Algorithm Steps:
- Convert to LAB: Convert both
C1 and C2 from their source format (e.g., RGB, Hex) into the Lab* color space components (L*,a*,b*).
- Apply LERP in LAB: Apply the same linear interpolation formula as above to the L*,a*, and b* components independently, for a given 't'.
- Convert Back to RGB: Convert the resulting Cnew in LAB space back into RGB space for display.
Algorithm Steps (HSL Example):
- Convert to HSL: Convert colors to HSL components {Hue H (0-360°), Saturation S, Lightness L (0-100%)}.
- Interpolate S and L linearly: Use the LERP formula for S and L.
- Interpolate Hue (Shortest Path): Hue is circular (0° wraps to 360°). To ensure the gradient takes the most visually appealing, shortest path around the color wheel (e.g., going from red 10° to blue 340° should go counter-clockwise through purple, not clockwise through yellow and green), a specialized LERP is used: Hnew = (H1 + t *ΔH) (mod[360]) Where ΔH is calculated to be the smaller angular difference between H1 and H2.
- Convert Back to RGB: Convert the resulting HSL color back to RGB for display..