Add support for gradient colours

color.go

@@ -236,3 +236,37 @@ func (cac CompleteAdaptiveColor) color() termenv.Color {
 func (cac CompleteAdaptiveColor) RGBA() (r, g, b, a uint32) {
 	return termenv.ConvertToRGB(cac.color()).RGBA()
 }
+
+// GradientColour specifies the start and end hex values for a colour gradient.
+// The RGBA is blended based on the position/steps parameters. During render the
+// gradient will be applied to the string provided, and the Steps parameter
+// will be set to the Width() of the string provided to render.
+// Currently only right to left gradient is supported.
+//
+// TODO: Add option for multiline:
+//  - corner to corner
+//  - radial
+//  - inverse
+type GradientColour struct {
+	Start    string
+	End      string
+	Steps    int
+	Position int
+}
+
+func (gc GradientColour) value() string {
+	sc := termenv.ConvertToRGB(ColorProfile().Color(gc.Start))
+	ec := termenv.ConvertToRGB(ColorProfile().Color(gc.End))
+
+	n := sc.BlendRgb(ec, float64(gc.Position)/float64(gc.Steps))
+
+	return n.Hex()
+}
+
+func (gc GradientColour) color() termenv.Color {
+	return ColorProfile().Color(gc.value())
+}
+
+func (gc GradientColour) RGBA() (r, g, b, a uint32) {
+	return termenv.ConvertToRGB(gc.color()).RGBA()
+}

color_test.go

@@ -213,6 +213,31 @@ func TestRGBA(t *testing.T) {
 			},
 			0xFF0000,
 		},
+		// lipgloss.GradientColour
+		{
+			termenv.TrueColor,
+			false,
+			GradientColour{Start: "#FF0000", End: "#0000FF", Steps: 10, Position: 0},
+			0xFF0000,
+		},
+		{
+			termenv.TrueColor,
+			true,
+			GradientColour{Start: "#FF0000", End: "#0000FF", Steps: 10, Position: 10},
+			0x0000FF,
+		},
+		{
+			termenv.TrueColor,
+			false,
+			GradientColour{Start: "#FF00FF", End: "#00FF00", Steps: 10, Position: 5},
+			0x808080,
+		},
+		{
+			termenv.TrueColor,
+			false,
+			GradientColour{Start: "#FF00FF", End: "#00FF00", Steps: 10, Position: 2},
+			0xCC33CC,
+		},
 	}
 
 	for i, tc := range tt {

style.go

@@ -167,8 +167,10 @@ func (s Style) Render(str string) string {
 		blink         = s.getAsBool(blinkKey, false)
 		faint         = s.getAsBool(faintKey, false)
 
-		fg = s.getAsColor(foregroundKey)
-		bg = s.getAsColor(backgroundKey)
+		fg                 = s.getAsColor(foregroundKey)
+		fggradient, fggrad = fg.(GradientColour)
+		bg                 = s.getAsColor(backgroundKey)
+		bggradient, bggrad = bg.(GradientColour)
 
 		width           = s.getAsInt(widthKey)
 		height          = s.getAsInt(heightKey)
@@ -227,24 +229,34 @@ func (s Style) Render(str string) string {
 	}
 
 	if fg != noColor {
-		fgc := fg.color()
-		te = te.Foreground(fgc)
-		if styleWhitespace {
-			teWhitespace = teWhitespace.Foreground(fgc)
-		}
-		if useSpaceStyler {
-			teSpace = teSpace.Foreground(fgc)
+		if fggrad {
+			fggradient.Position = 0
+			fggradient.Steps = Width(str)
+		} else {
+			fgc := fg.color()
+			te = te.Foreground(fgc)
+			if styleWhitespace {
+				teWhitespace = teWhitespace.Foreground(fgc)
+			}
+			if useSpaceStyler {
+				teSpace = teSpace.Foreground(fgc)
+			}
 		}
 	}
 
 	if bg != noColor {
-		bgc := bg.color()
-		te = te.Background(bgc)
-		if colorWhitespace {
-			teWhitespace = teWhitespace.Background(bgc)
-		}
-		if useSpaceStyler {
-			teSpace = teSpace.Background(bgc)
+		if bggrad {
+			bggradient.Position = 0
+			bggradient.Steps = Width(str)
+		} else {
+			bgc := bg.color()
+			te = te.Background(bgc)
+			if colorWhitespace {
+				teWhitespace = teWhitespace.Background(bgc)
+			}
+			if useSpaceStyler {
+				teSpace = teSpace.Background(bgc)
+			}
 		}
 	}
 
@@ -280,15 +292,37 @@ func (s Style) Render(str string) string {
 
 		l := strings.Split(str, "\n")
 		for i := range l {
-			if useSpaceStyler {
+			var fte, fteSpace termenv.Style
+			if i == 0 {
+				fte, fteSpace = te, teSpace
+			}
+			if useSpaceStyler || fggrad || bggrad {
 				// Look for spaces and apply a different styler
 				for _, r := range l[i] {
+					if fggrad {
+						te = fte.Foreground(fggradient.color())
+						teSpace = fteSpace.Foreground(fggradient.color())
+						fggradient.Position++
+					}
+					if bggrad {
+						te = fte.Background(bggradient.color())
+						teSpace = fteSpace.Background(bggradient.color())
+						bggradient.Position++
+					}
+
 					if unicode.IsSpace(r) {
 						b.WriteString(teSpace.Styled(string(r)))
 						continue
 					}
 					b.WriteString(te.Styled(string(r)))
 				}
+
+				if fggrad {
+					fggradient.Position = 0
+				}
+				if bggrad {
+					bggradient.Position = 0
+				}
 			} else {
 				b.WriteString(te.Styled(l[i]))
 			}

style_test.go

@@ -18,6 +18,10 @@ func TestStyleRender(t *testing.T) {
 			NewStyle().Foreground(Color("#5A56E0")),
 			"\x1b[38;2;89;86;224mhello\x1b[0m",
 		},
+		{
+			NewStyle().Background(GradientColour{Start: "#00FF00", End: "#FF00FF"}),
+			"\x1b[48;2;0;255;0mh\x1b[0m\x1b[48;2;51;204;51me\x1b[0m\x1b[48;2;102;153;102ml\x1b[0m\x1b[48;2;153;102;153ml\x1b[0m\x1b[48;2;204;51;204mo\x1b[0m",
+		},
 		{
 			NewStyle().Bold(true),
 			"\x1b[1mhello\x1b[0m",