feat: support rounded rect for bar chart

bar_chart.go

@@ -142,14 +142,25 @@ func (b *barChart) render(result *defaultRenderResult, seriesList SeriesList) (B
 			}
 			top := barMaxHeight - h
 
-			seriesPainter.OverrideDrawingStyle(Style{
-				FillColor: fillColor,
-			}).Rect(chart.Box{
-				Top:    top,
-				Left:   x,
-				Right:  x + barWidth,
-				Bottom: barMaxHeight - 1,
-			})
+			if series.RoundRadius <= 0 {
+				seriesPainter.OverrideDrawingStyle(Style{
+					FillColor: fillColor,
+				}).Rect(chart.Box{
+					Top:    top,
+					Left:   x,
+					Right:  x + barWidth,
+					Bottom: barMaxHeight - 1,
+				})
+			} else {
+				seriesPainter.OverrideDrawingStyle(Style{
+					FillColor: fillColor,
+				}).RoundedRect(chart.Box{
+					Top:    top,
+					Left:   x,
+					Right:  x + barWidth,
+					Bottom: barMaxHeight - 1,
+				}, series.RoundRadius)
+			}
 			// 用于生成marker point
 			points[j] = Point{
 				// 居中的位置

painter.go

@@ -803,6 +803,48 @@ func (p *Painter) Rect(box Box) *Painter {
 	return p
 }
 
+func (p *Painter) RoundedRect(box Box, radius int) *Painter {
+	r := (box.Right - box.Left) / 2
+	if radius > r {
+		radius = r
+	}
+	rx := float64(radius)
+	ry := float64(radius)
+	p.MoveTo(box.Left+radius, box.Top)
+	p.LineTo(box.Right-radius, box.Top)
+
+	cx := box.Right - radius
+	cy := box.Top + radius
+	// right top
+	p.ArcTo(cx, cy, rx, ry, -math.Pi/2, math.Pi/2)
+
+	p.LineTo(box.Right, box.Bottom-radius)
+
+	// right bottom
+	cx = box.Right - radius
+	cy = box.Bottom - radius
+	p.ArcTo(cx, cy, rx, ry, 0.0, math.Pi/2)
+
+	p.LineTo(box.Left+radius, box.Bottom)
+
+	// left bottom
+	cx = box.Left + radius
+	cy = box.Bottom - radius
+	p.ArcTo(cx, cy, rx, ry, math.Pi/2, math.Pi/2)
+
+	p.LineTo(box.Left, box.Top+radius)
+
+	// left top
+	cx = box.Left + radius
+	cy = box.Top + radius
+	p.ArcTo(cx, cy, rx, ry, math.Pi, math.Pi/2)
+
+	p.Close()
+	p.FillStroke()
+	p.Fill()
+	return p
+}
+
 func (p *Painter) LegendLineDot(box Box) *Painter {
 	width := box.Width()
 	height := box.Height()

painter_test.go

@@ -343,6 +343,29 @@ func TestPainter(t *testing.T) {
 	}
 }
 
+func TestRoundedRect(t *testing.T) {
+	assert := assert.New(t)
+	p, err := NewPainter(PainterOptions{
+		Width:  400,
+		Height: 300,
+		Type:   ChartOutputSVG,
+	})
+	assert.Nil(err)
+	p.OverrideDrawingStyle(Style{
+		FillColor:   drawing.ColorWhite,
+		StrokeWidth: 1,
+		StrokeColor: drawing.ColorWhite,
+	}).RoundedRect(Box{
+		Left:   10,
+		Right:  30,
+		Bottom: 150,
+		Top:    10,
+	}, 5)
+	buf, err := p.Bytes()
+	assert.Nil(err)
+	assert.Equal("<svg xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\" width=\"400\" height=\"300\">\\n<path  d=\"M 15 10\nL 25 10\nL 25 10\nA 5 5 90.00 0 1 30 15\nL 30 145\nL 30 145\nA 5 5 90.00 0 1 25 150\nL 15 150\nL 15 150\nA 5 5 90.00 0 1 10 145\nL 10 15\nL 10 15\nA 5 5 90.00 0 1 15 10\nZ\" style=\"stroke-width:1;stroke:rgba(255,255,255,1.0);fill:rgba(255,255,255,1.0)\"/><path  d=\"\" style=\"stroke-width:1;stroke:rgba(255,255,255,1.0);fill:rgba(255,255,255,1.0)\"/></svg>", string(buf))
+}
+
 func TestPainterTextFit(t *testing.T) {
 	assert := assert.New(t)
 	p, err := NewPainter(PainterOptions{

series.go

@@ -126,6 +126,8 @@ type Series struct {
 	Name string
 	// Radius for Pie chart, e.g.: 40%, default is "40%"
 	Radius string
+	// Round for bar chart
+	RoundRadius int
 	// Mark point for series
 	MarkPoint SeriesMarkPoint
 	// Make line for series