math - 如何计算两种颜色之间的差异（亮度、亮度、颜色）？

Question

我该如何计算

• 亮度对比度，
• 亮度差异，以及
• 颜色的差异

在两种给定的颜色之间？

例子：

输入

• 颜色 1：#99ccff
• 颜色 2：#225588

输出

• 亮度对比度：4.57：1
• 亮度差异：119
• 色差：357

Answer 1

Convert each colour from (R, G, B) to (H, S, V) [or (H, S, L)] coordinates. You can find formulae at Wikipedia.

I have written Pascal functions for this:

function RGBToHSV(const Color: TRGB): THSV;
var
  cmax, cmin, cdiff: real;
begin
  cmax := MaxComponent(Color);
  cmin := MinComponent(Color);
  cdiff := cmax - cmin;

  with Color, result do
  begin

    // Hue
    if cmax = cmin then
      hsvHue := 0
    else if cmax = rgbRed then
      hsvHue := (60 * (rgbGreen - rgbBlue) / cdiff)
    else if cmax = rgbGreen then
      hsvHue := (60 * (rgbBlue - rgbRed) / cdiff) + 120
    else
      hsvHue := (60 * (rgbRed - rgbGreen) / cdiff) + 240;

    hsvHue := Fix360(hsvHue);

    // Saturation
    if cmax = 0 then
      hsvSaturation := 0
    else
      hsvSaturation := 1 - cmin / cmax;

    // Value
    hsvValue := cmax;

  end;

end;

function RGBToHSL(const Color: TRGB): THSL;
var
  cmax, cmin, cdiff, csum: real;
begin
  cmax := MaxComponent(Color);
  cmin := MinComponent(Color);
  cdiff := cmax - cmin;
  csum := cmax + cmin;

  with Color, result do
  begin

    // Hue
    if cmax = cmin then
      hslHue := 0
    else if cmax = rgbRed then
      hslHue := (60 * (rgbGreen - rgbBlue) / cdiff)
    else if cmax = rgbGreen then
      hslHue := (60 * (rgbBlue - rgbRed) / cdiff) + 120
    else
      hslHue := (60 * (rgbRed - rgbGreen) / cdiff) + 240;

    hslHue := Fix360(hslHue);

    // Saturation
    if cmax = cmin then
      hslSaturation := 0
    else if csum <= 1 then
      hslSaturation := cdiff / csum
    else
      hslSaturation := cdiff / (2 - csum);

    // Lightness
    hslLightness := csum / 2;

  end;

end;