Perceived Brightness HSP Calculator
Compute normalized HSP heuristic brightness from gamma-encoded sRGB with fixed .299/.587/.114 squared weights; not relative luminance, WCAG contrast, or individual perception.
Description
HSP brightness is a weighted root of squared encoded channels.
HSP brightness is a weighted root of squared encoded channels. It is a perception heuristic distinct from relative luminance.1
Enter exactly three encoded normalized sRGB channels 0–1. Return normalized heuristic brightness.
When to use Perceived Brightness HSP Calculator
Use Perceived Brightness HSP Calculator when you need to evaluate the supplied records under the calculation and evidence rules below. No individual perception or WCAG contrast is established.
Prepare colors in the stated color space and scale. Use encoded RGB fractions, linear RGB, Lab, xy, byte values or ink percentages exactly as requested; supply caller tolerances and reference conditions.
How to use Perceived Brightness HSP Calculator and understand its results
- Prepare colors in the stated color space and scale. Use encoded RGB fractions, linear RGB, Lab, xy, byte values or ink percentages exactly as requested; supply caller tolerances and reference conditions.
- Enter rgbChannels using the field table and calculation rules, then run the tool.
- Read hspPerceivedBrightness. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| rgbChannels | Rgb channels | list of number | Required |
Enter exactly three encoded normalized sRGB channels 0–1. Return normalized heuristic brightness.
brightness=sqrt(0.299R²+0.587G²+0.114B²) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| hspPerceivedBrightness | Hsp perceived brightness | number |
{
"input": {
"rgbChannels": [
1,
0,
0
]
},
"output": {
"hspPerceivedBrightness": 0.5468089245796927
}
}Limitations and assumptions
No individual perception or WCAG contrast is established.
Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Numeric lists are limited to 10,000 entries; string lists to 128 strings of at most 128 characters each. The rules above may impose smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use YIQ Luma Value Calculator: YIQ luma combines encoded color channels with legacy weights. It differs from linear-light relative luminance. For a complementary task, use Auto Black/White Text Picker: Opaque background relative luminance determines black and white text contrast. The larger ratio is an objective choice within these two candidates.
References
-
Perceived Brightness HSP Calculator — tool.io
Similar or alternative tools
- YIQ Luma Value Calculator
YIQ luma combines encoded color channels with legacy weights. It differs from linear-light relative luminance.
- Auto Black/White Text Picker
Opaque background relative luminance determines black and white text contrast. The larger ratio is an objective choice within these two candidates.