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Convert between colour spaces

Source: R/utils_imagem.R
utils_colorspace.Rd

  • rgb_to_srgb() Transforms colors from RGB space (red/green/blue) to Standard Red Green Blue (sRGB), using a gamma correction of 2.2. The function performs the conversion by applying a gamma correction to the input RGB values (raising them to the power of 2.2) and then transforming them using a specific transformation matrix. The result is clamped to the range 0-1 to ensure valid sRGB values.

  • rgb_to_hsb() Transforms colors from RGB space (red/green/blue) to HSB space (hue/saturation/brightness). The HSB values are calculated as follows (see https://www.rapidtables.com/convert/color/rgb-to-hsv.html for more details).

    • Hue: The hue is determined based on the maximum value among R, G, and B, and it ranges from 0 to 360 degrees.

    • Saturation: Saturation is calculated as the difference between the maximum and minimum channel values, expressed as a percentage.

    • Brightness: Brightness is equal to the maximum channel value, expressed as a percentage.

  • rgb_to_lab() Transforms colors from RGB space (red/green/blue) to CIE-LAB space, using the sRGB values. See grDevices::convertColor() for more details.

Usage

rgb_to_hsb(object)

rgb_to_srgb(object)

rgb_to_lab(object)

Arguments

object

An Image object, an object computed with analyze_objects() with a valid object_index argument, or a data.frame/matrix. For the last, a three-column data (R, G, and B, respectively) is required.

Value

A data frame with the columns of the converted color space

References

See the detailed formulas here

Author

Tiago Olivoto tiagoolivoto@gmail.com

Examples

if (interactive() && requireNamespace("EBImage")) {
library(pliman)
img <- image_pliman("sev_leaf.jpg")
rgb_to_lab(img)

# analyze the object and convert the pixels
anal <- analyze_objects(img, object_index = "B", pixel_level_index = TRUE)
rgb_to_lab(anal)
}