nvim-fade-color

Fade RGB color between two given colors by percentage.

Installation

Using packer in lua

use ("ksk0/nvim-fade-color")

Using vim-plug in vimscript

Plug 'ks0/nvim-fade-color'

Usage

faded_color = require("fade-color").fade(src_color, dst_color, fade)

where:

• fade is number from 0 to 1 (representing percentage)
• src_color is color to be faded
• dst_color color to achieve when fade is 100% (fade = 1)
• faded_color is resulting (faded) color

Value of src_color, dst_color and fade_color

Input values cane be given either as number:

src_color = 34563345

or as list of RGB values:

src_color = {126, 224, 68}

while faded_color format depends of format of src_value. If number, fade_color will be number, and if src_value is list, fade_color will also be list of RGB values.

How and why

Fading can be done, by adjusting each RGB color separately in range between source and destination color. If faded that way, at 0% faded color will be equal to source color and when fade for 100% faded color will be equal to destination color. By fading this way, in full transition we will cross entire color spectrum between source and destination color.

This plugin uses HSL (Hue Saturation Lightness) color representation for faded color calculation. In HSL representation, Hue represents color, while Saturation and Lightness basically represent intensity of a color.

Calculation is done on HSL values, and later converted to RGB values. The formula is:

faded_S = (1-fade) * source_S + fade * destination_S
faded_L = (1-fade) * source_L + fade * destination_L
faded_H = source_H

Where fade is value between 0 and 1 (1 being 100%). By changing only Saturation and Lightness we achieve that, base color is preserved, and only intensity of color is changed. When fade = 0 faded color is same as source color. When fade = 1 faded color DOES NOT equal to destination color. Only S and L values are equal to that of destination color, thus faded color is equal in intensity to destination, but with same color as source one.

This yields good results, when used to fade text to the background color, preserving color of the text, but fading it to the background color intensity. The quality of the result depends on, foreground and background colors.

You can test the results with this script:

local fader = require("fade-color")

local hi_normal = vim.api.nvim_get_hl_by_name("Normal", true)
local hi_error  = vim.api.nvim_get_hl_by_name("ErrorMsg", true)

local src_col = hi_error.foreground
local dst_col = hi_normal.background
local shades  = 10

for i = 0, shades do
  local fade = i * (1 / shades)
  local faded_col = fader.fade(src_col, dst_col, fade)
  local hi_name   = string.format("FaderTestHighlight_%02d", i)

  vim.cmd("highlight " .. hi_name .. " guifg=#" .. string.format("%06x", faded_col))
  vim.cmd("hi " .. hi_name)
end

Script will create 10 Highlights and in command line print their definition, thus showing how text in ErrorMsg color, fades into Normal background.

More info on HSL representation here: wiki page