Provide Color constant references in chartdraw package

The need to use `drawing` to reference specific colors was non-obvious to new users.
This change puts all previous (and some new) color constants in the `charts` package, making them easier to find and use.

axis_test.go

@@ -7,7 +7,6 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"github.com/go-analyze/charts/chartdraw"
-	"github.com/go-analyze/charts/chartdraw/drawing"
 )
 
 func TestAxis(t *testing.T) {
@@ -201,7 +200,7 @@ func TestAxis(t *testing.T) {
 					Data: letterLabels,
 					FontStyle: FontStyle{
 						FontSize:  40.0,
-						FontColor: drawing.ColorBlue,
+						FontColor: ColorBlue,
 					},
 				}
 			},
@@ -232,8 +231,8 @@ func TestAxis(t *testing.T) {
 	axisTheme := MakeTheme(ThemeOption{
 		IsDarkMode:         false,
 		AxisStrokeColor:    Color{R: 110, G: 112, B: 121, A: 255},
-		AxisSplitLineColor: drawing.ColorBlack,
-		BackgroundColor:    drawing.ColorWhite,
+		AxisSplitLineColor: ColorBlack,
+		BackgroundColor:    ColorWhite,
 		TextColor:          Color{R: 70, G: 70, B: 70, A: 255},
 	})
 	for i, tt := range tests {

bar_chart_test.go

@@ -6,8 +6,6 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-
-	"github.com/go-analyze/charts/chartdraw/drawing"
 )
 
 func makeBasicBarChartOption() BarChartOption {
@@ -111,7 +109,7 @@ func TestBarChart(t *testing.T) {
 				opt := makeBasicBarChartOption()
 				customFont := FontStyle{
 					FontSize:  4.0,
-					FontColor: drawing.ColorBlue,
+					FontColor: ColorBlue,
 				}
 				opt.Legend.FontStyle = customFont
 				opt.XAxis.FontStyle = customFont

benchmark_test.go

@@ -3,8 +3,6 @@ package charts
 import (
 	"errors"
 	"testing"
-
-	"github.com/go-analyze/charts/chartdraw"
 )
 
 func makeDefaultMultiChartOptions() ChartOption {
@@ -18,7 +16,7 @@ func makeDefaultMultiChartOptions() ChartOption {
 				"Milk Tea", "Matcha Latte", "Cheese Cocoa", "Walnut Brownie",
 			},
 		},
-		Padding: chartdraw.Box{
+		Padding: Box{
 			Top:    10,
 			Right:  10,
 			Bottom: 10,
@@ -53,7 +51,7 @@ func makeDefaultMultiChartOptions() ChartOption {
 						"Milk Tea", "Matcha Latte", "Cheese Cocoa", "Walnut Brownie",
 					},
 				},
-				Box: chartdraw.Box{
+				Box: Box{
 					Top:    20,
 					Left:   400,
 					Right:  500,

color.go

@@ -2,10 +2,120 @@ package charts
 
 import (
 	"math"
+	"strings"
 
+	"github.com/go-analyze/charts/chartdraw"
 	"github.com/go-analyze/charts/chartdraw/drawing"
 )
 
+var (
+	// ColorTransparent is a fully transparent color.
+	ColorTransparent = drawing.ColorTransparent
+	// ColorWhite is R: 255, G: 255, B: 255.
+	ColorWhite = drawing.ColorWhite
+	// ColorBlack is R: 0, G: 0, B: 0.
+	ColorBlack = drawing.ColorBlack
+	// ColorGray is R: 128, G: 128, B: 128.
+	ColorGray = drawing.ColorGray
+	// ColorRed is R: 255, G: 0, B: 0.
+	ColorRed = drawing.ColorRed
+	// ColorGreen is R: 0, G: 128, B: 0.
+	ColorGreen = drawing.ColorGreen
+	// ColorBlue is R: 0, G: 0, B: 255.
+	ColorBlue = drawing.ColorBlue
+	// ColorSilver is R: 192, G: 192, B: 192.
+	ColorSilver = drawing.ColorSilver
+	// ColorMaroon is R: 128, G: 0, B: 0.
+	ColorMaroon = drawing.ColorMaroon
+	// ColorPurple is R: 128, G: 0, B: 128.
+	ColorPurple = drawing.ColorPurple
+	// ColorFuchsia is R: 255, G: 0, B: 255.
+	ColorFuchsia = drawing.ColorFuchsia
+	// ColorLime is R: 0, G: 255, B: 0.
+	ColorLime = drawing.ColorLime
+	// ColorOlive is R: 128, G: 128, B: 0.
+	ColorOlive = drawing.ColorOlive
+	// ColorYellow is R: 255, G: 255, B: 0.
+	ColorYellow = drawing.ColorYellow
+	// ColorNavy is R: 0, G: 0, B: 128.
+	ColorNavy = drawing.ColorNavy
+	// ColorTeal is R: 0, G: 128, B: 128.
+	ColorTeal = drawing.ColorTeal
+	// ColorAqua (or Cyan) is R: 0, G: 255, B: 255.
+	ColorAqua = drawing.ColorAqua
+	// ColorDarkGray is R: 40, G: 40, B: 40.
+	ColorDarkGray = Color{R: 40, G: 40, B: 40, A: 255}
+	// ColorLightGray is R: 211, G: 211, B: 211.
+	ColorLightGray = drawing.ColorLightGray
+	// ColorSlateGray is R: 112, G: 128, B: 144.
+	ColorSlateGray = drawing.ColorSlateGray
+	// ColorLightSlateGray is R: 119, G: 136, B: 211.
+	ColorLightSlateGray = drawing.ColorLightSlateGray
+	// ColorAzure is R: 240, G: 255, B: 255.
+	ColorAzure = drawing.ColorAzure
+	// ColorBeige is R: 245, G: 245, B: 220.
+	ColorBeige = drawing.ColorBeige
+	// ColorBrown is R: 165, G: 42, B: 42.
+	ColorBrown = drawing.ColorBrown
+	// ColorChocolate is R: 210, G: 105, B: 30.
+	ColorChocolate = drawing.ColorChocolate
+	// ColorCoral is R: 255, G: 127, B: 80.
+	ColorCoral = drawing.ColorCoral
+	// ColorGold is R: 255, G: 215, B: 0.
+	ColorGold = drawing.ColorGold
+	// ColorIndigo is R: 75, G: 0, B: 130.
+	ColorIndigo = drawing.ColorIndigo
+	// ColorIvory is R: 255, G: 255, B: 250.
+	ColorIvory = drawing.ColorIvory
+	// ColorOrange is R: 255, G: 165, B: 0.
+	ColorOrange = drawing.ColorOrange
+	// ColorPink is R: 255, G: 192, B: 203.
+	ColorPink = drawing.ColorPink
+	// ColorPlum is R: 221, G: 160, B: 221.
+	ColorPlum = drawing.ColorPlum
+	// ColorSalmon is R: 250, G: 128, B: 114.
+	ColorSalmon = drawing.ColorSalmon
+	// ColorTan is R: 210, G: 180, B: 140.
+	ColorTan = drawing.ColorTan
+	// ColorKhaki is R: 240, G: 230, B: 140.
+	ColorKhaki = drawing.ColorKhaki
+	// ColorTurquoise is R: 64, G: 224, B: 208.
+	ColorTurquoise = drawing.ColorTurquoise
+	// ColorViolet is R: 238, G: 130, B: 238.
+	ColorViolet = drawing.ColorViolet
+
+	// alternate non-standard shades //
+
+	// ColorBlackAlt1 is slightly lighter shade of black: R: 51, G: 51, B: 51.
+	ColorBlackAlt1 = chartdraw.ColorBlack
+	// ColorBlueAlt1 is lighter shade of blue: R:0, G: 116, B: 217.
+	ColorBlueAlt1 = chartdraw.ColorBlue
+	// ColorBlueAlt2 is a sea blue: R: 106, G: 195, B: 203.
+	ColorBlueAlt2 = chartdraw.ColorAlternateBlue
+	// ColorAquaAlt1 is a lighter aqua: R: 0, G: 217, B: 210.
+	ColorAquaAlt1 = chartdraw.ColorCyan
+	// ColorGreenAlt1 is lighter green: R: 0, G: 217, B: 101.
+	ColorGreenAlt1 = chartdraw.ColorGreen
+	// ColorGreenAlt2 is R: 42, G: 190, B: 137.
+	ColorGreenAlt2 = chartdraw.ColorAlternateGreen
+	// ColorGreenAlt3 is darker green: R: 59, G: 162, B: 114.
+	ColorGreenAlt3 = Color{R: 59, G: 162, B: 114, A: 255}
+	// ColorGreenAlt4 is darker green: R: 80, G: 134, B: 66.
+	ColorGreenAlt4 = Color{R: 80, G: 143, B: 66, A: 255}
+	// ColorRedAlt1 is slightly purple red: R: 217, G: 0, B: 116.
+	ColorRedAlt1 = chartdraw.ColorRed
+	// ColorRedAlt2 is darker purple red: R: 226, G: 77, B: 66.
+	ColorRedAlt2 = Color{R: 226, G: 77, B: 66, A: 255}
+	// ColorOrangeAlt1 is more typical orange: R: 217, G: 101, B: 0.
+	ColorOrangeAlt1 = chartdraw.ColorOrange
+	// ColorOrangeAlt2 is a lighter orange: R: 250, G: 200, B: 88.
+	ColorOrangeAlt2 = Color{R: 250, G: 200, B: 88, A: 255}
+	// ColorOrangeAlt3 is a lighter orange: R: 255, G: 152, B: 69.
+	ColorOrangeAlt3 = Color{R: 255, G: 152, B: 69, A: 255}
+	// ColorYellowAlt1 is a slightly darker yellow: R: 217, G: 210, B: 0.
+	ColorYellowAlt1 = chartdraw.ColorYellow
+)
+
 func isLightColor(c Color) bool {
 	r := float64(c.R) * float64(c.R) * 0.299
 	g := float64(c.G) * float64(c.G) * 0.587
@@ -15,6 +125,33 @@ func isLightColor(c Color) bool {
 
 // ParseColor parses a color from a string. The color can be specified in hex with a `#` prefix (for example '#313233'),
 // in rgb(i,i,i) or rgba(i,i,i,f) format, or as a common name (for example 'red').
-func ParseColor(color string) Color {
-	return drawing.ParseColor(color)
+func ParseColor(rawColor string) Color {
+	if strings.HasPrefix(rawColor, "#") {
+		return ColorFromHex(rawColor)
+	} else if strings.HasPrefix(rawColor, "rgb") {
+		return ColorFromRGBA(rawColor)
+	}
+	return ColorFromKnown(rawColor)
+}
+
+// ColorFromKnown returns an internal color from a known (basic) color name.
+func ColorFromKnown(known string) Color {
+	return drawing.ColorFromKnown(known)
+}
+
+// ColorFromHex returns a color from a css hex code.
+//
+// NOTE: it will trim a leading '#' character if present.
+func ColorFromHex(hex string) Color {
+	return drawing.ColorFromHex(hex)
+}
+
+// ColorFromRGBA returns a color from a `rgb(i,i,i)` or `rgba(i,i,i,f)` css function.
+func ColorFromRGBA(color string) Color {
+	return drawing.ColorFromRGBA(color)
+}
+
+// ColorFromRGBAValues returns the system alpha mixed rgba values.
+func ColorFromRGBAValues(r, g, b, a uint32) Color {
+	return drawing.ColorFromAlphaMixedRGBA(r, g, b, a)
 }

color_test.go

@@ -4,19 +4,91 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
-
-	"github.com/go-analyze/charts/chartdraw/drawing"
+	"github.com/stretchr/testify/require"
 )
 
+func BenchmarkParseColor(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		_ = ParseColor("#333")
+		_ = ParseColor("#313233")
+		_ = ParseColor("rgb(31,32,33)")
+		_ = ParseColor("rgba(50,51,52,250)")
+	}
+}
+
+func BenchmarkColorString(b *testing.B) {
+	c := ParseColor("rgb(31,32,33)")
+	for i := 0; i < b.N; i++ {
+		_ = c.String()
+	}
+}
+
+const makeColorShadeSamples = false
+
+func testColorShades(t *testing.T, colors ...Color) {
+	if !makeColorShadeSamples {
+		return // color samples are generated through a test failure
+	}
+	t.Helper()
+
+	p := NewPainter(PainterOptions{
+		OutputFormat: ChartOutputSVG,
+		Width:        600,
+		Height:       400,
+	})
+
+	sampleWidth := p.Width() / len(colors)
+	for i, c := range colors {
+		p.FilledRect(i*sampleWidth, 0, (i+1)*sampleWidth, p.Height(),
+			c, ColorTransparent, 0.0)
+	}
+
+	data, err := p.Bytes()
+	require.NoError(t, err)
+	assertEqualSVG(t, "", data)
+}
+
+func TestGrayColors(t *testing.T) {
+	testColorShades(t, ColorDarkGray, ColorGray, ColorLightGray)
+}
+
+func TestBlueColors(t *testing.T) {
+	testColorShades(t, ColorBlue, ColorBlueAlt1, ColorBlueAlt2)
+}
+
+func TestGreenColors(t *testing.T) {
+	testColorShades(t, ColorGreen, ColorGreenAlt1, ColorGreenAlt2, ColorGreenAlt3, ColorGreenAlt4)
+}
+
+func TestRedColors(t *testing.T) {
+	testColorShades(t, ColorRed, ColorRedAlt1, ColorRedAlt2)
+}
+
+func TestOrangeColors(t *testing.T) {
+	testColorShades(t, ColorOrange, ColorOrangeAlt1, ColorOrangeAlt2, ColorOrangeAlt3)
+}
+
+func TestAquaColors(t *testing.T) {
+	testColorShades(t, ColorAqua, ColorAquaAlt1)
+}
+
+func TestYellowColors(t *testing.T) {
+	testColorShades(t, ColorYellow, ColorYellowAlt1)
+}
+
+func TestPurpleColors(t *testing.T) {
+	testColorShades(t, ColorPurple, ColorViolet, ColorPlum, ColorFuchsia)
+}
+
 func TestIsLightColor(t *testing.T) {
 	t.Parallel()
 
-	assert.True(t, isLightColor(drawing.Color{R: 255, G: 255, B: 255}))
-	assert.True(t, isLightColor(drawing.Color{R: 145, G: 204, B: 117}))
+	assert.True(t, isLightColor(Color{R: 255, G: 255, B: 255}))
+	assert.True(t, isLightColor(Color{R: 145, G: 204, B: 117}))
 
-	assert.False(t, isLightColor(drawing.Color{R: 88, G: 112, B: 198}))
-	assert.False(t, isLightColor(drawing.Color{R: 0, G: 0, B: 0}))
-	assert.False(t, isLightColor(drawing.Color{R: 16, G: 12, B: 42}))
+	assert.False(t, isLightColor(Color{R: 88, G: 112, B: 198}))
+	assert.False(t, isLightColor(Color{R: 0, G: 0, B: 0}))
+	assert.False(t, isLightColor(Color{R: 16, G: 12, B: 42}))
 }
 
 func TestParseColor(t *testing.T) {
@@ -26,33 +98,17 @@ func TestParseColor(t *testing.T) {
 	assert.True(t, c.IsZero())
 
 	c = ParseColor("#333")
-	assert.Equal(t, drawing.Color{R: 51, G: 51, B: 51, A: 255}, c)
+	assert.Equal(t, Color{R: 51, G: 51, B: 51, A: 255}, c)
 
 	c = ParseColor("#313233")
-	assert.Equal(t, drawing.Color{R: 49, G: 50, B: 51, A: 255}, c)
+	assert.Equal(t, Color{R: 49, G: 50, B: 51, A: 255}, c)
 
 	c = ParseColor("rgb(31,32,33)")
-	assert.Equal(t, drawing.Color{R: 31, G: 32, B: 33, A: 255}, c)
+	assert.Equal(t, Color{R: 31, G: 32, B: 33, A: 255}, c)
 
 	c = ParseColor("rgba(50,51,52,.981)")
-	assert.Equal(t, drawing.Color{R: 50, G: 51, B: 52, A: 250}, c)
+	assert.Equal(t, Color{R: 50, G: 51, B: 52, A: 250}, c)
 
 	c = ParseColor("rgba(50,51,52,250)")
-	assert.Equal(t, drawing.Color{R: 50, G: 51, B: 52, A: 250}, c)
-}
-
-func BenchmarkParseColor(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		_ = ParseColor("#333")
-		_ = ParseColor("#313233")
-		_ = ParseColor("rgb(31,32,33)")
-		_ = ParseColor("rgba(50,51,52,250)")
-	}
-}
-
-func BenchmarkColorString(b *testing.B) {
-	c := ParseColor("rgb(31,32,33)")
-	for i := 0; i < b.N; i++ {
-		_ = c.String()
-	}
+	assert.Equal(t, Color{R: 50, G: 51, B: 52, A: 250}, c)
 }

echarts.go

@@ -136,7 +136,7 @@ func (ey *EChartsYAxis) UnmarshalJSON(data []byte) error {
 }
 
 type EChartsPadding struct {
-	Box chartdraw.Box
+	Box Box
 }
 
 func (eb *EChartsPadding) UnmarshalJSON(data []byte) error {
@@ -344,7 +344,7 @@ type EChartsOption struct {
 	Theme      string         `json:"theme"`
 	FontFamily string         `json:"fontFamily"`
 	Padding    EChartsPadding `json:"padding"`
-	Box        chartdraw.Box  `json:"box"`
+	Box        Box            `json:"box"`
 	Width      int            `json:"width"`
 	Height     int            `json:"height"`
 	Title      struct {