added an example

examples/drawing/drawing.go

@@ -0,0 +1,121 @@
+package main
+
+import (
+	"image/color"
+	"log"
+	"math"
+
+	"github.com/tfriedel6/canvas"
+	"github.com/tfriedel6/canvas/sdlcanvas"
+)
+
+func main() {
+	wnd, cv, err := sdlcanvas.CreateWindow(1280, 720, "Canvas Test")
+	if err != nil {
+		log.Println(err)
+		return
+	}
+	defer wnd.Destroy()
+
+	lg := canvas.NewLinearGradient(320, 200, 480, 520)
+	lg.AddColorStop(0, "#ff000040")
+	lg.AddColorStop(1, "#00ff0040")
+	lg.AddColorStop(0.5, "#0000ff40")
+
+	rg := canvas.NewRadialGradient(540, 300, 80, 740, 300, 100)
+	rg.AddColorStop(0, "#ff0000")
+	rg.AddColorStop(1, "#00ff00")
+	rg.AddColorStop(0.5, "#0000ff")
+
+	wnd.MainLoop(func() {
+		w, h := float64(cv.Width()), float64(cv.Height())
+
+		// Clear the screen
+		cv.SetFillStyle("#000")
+		cv.FillRect(0, 0, w, h)
+
+		// Draw lines with different colors and line thickness
+		for x := 1.0; x < 10.5; x += 1.0 {
+			cv.SetStrokeStyle(int(x*25), 255, 255)
+			cv.SetLineWidth(x)
+			cv.BeginPath()
+			cv.MoveTo(x*10+20, 20)
+			cv.LineTo(x*10+20, 120)
+			cv.Stroke()
+		}
+
+		// Draw a path
+		cv.BeginPath()
+		cv.MoveTo(160, 20)
+		cv.LineTo(180, 20)
+		cv.LineTo(180, 40)
+		cv.LineTo(200, 40)
+		cv.LineTo(200, 60)
+		cv.LineTo(220, 60)
+		cv.LineTo(220, 80)
+		cv.LineTo(240, 80)
+		cv.LineTo(240, 100)
+		cv.LineTo(260, 100)
+		cv.LineTo(260, 120)
+		cv.ArcTo(160, 120, 160, 100, 20)
+		cv.ClosePath()
+		cv.SetStrokeStyle(color.RGBA{R: 255, G: 128, B: 128, A: 255})
+		cv.SetLineWidth(4)
+		cv.Stroke()
+
+		// Fill a polygon
+		cv.BeginPath()
+		cv.MoveTo(300, 20)
+		cv.LineTo(340, 20)
+		cv.QuadraticCurveTo(370, 20, 370, 50)
+		cv.QuadraticCurveTo(370, 80, 400, 80)
+		cv.LineTo(400, 80)
+		cv.LineTo(400, 120)
+		cv.LineTo(360, 120)
+		cv.BezierCurveTo(330, 120, 330, 80, 300, 80)
+		cv.ClosePath()
+		cv.SetFillStyle(color.RGBA{R: 128, G: 255, B: 128, A: 255})
+		cv.Fill()
+
+		// Draw with alpha
+		cv.SetGlobalAlpha(0.5)
+		cv.SetFillStyle("#FF0000")
+		cv.BeginPath()
+		cv.Arc(100, 275, 60, 0, math.Pi*2, false)
+		cv.Fill()
+		cv.SetFillStyle("#00FF00")
+		cv.BeginPath()
+		cv.Arc(140, 210, 60, 0, math.Pi*2, false)
+		cv.Fill()
+		cv.SetFillStyle("#0000FF")
+		cv.BeginPath()
+		cv.Arc(180, 275, 60, 0, math.Pi*2, false)
+		cv.Fill()
+		cv.SetGlobalAlpha(1)
+
+		// Clipped drawing
+		cv.Save()
+		cv.BeginPath()
+		cv.Arc(340, 240, 80, 0, math.Pi*2, true)
+		cv.Clip()
+		cv.SetStrokeStyle(0, 255, 0)
+		for x := 1.0; x < 12.5; x += 1.0 {
+			cv.BeginPath()
+			cv.MoveTo(260, 140+16*x)
+			cv.LineTo(420, 140+16*x)
+			cv.Stroke()
+		}
+		cv.SetFillStyle(0, 0, 255)
+		for x := 1.0; x < 12.5; x += 1.0 {
+			cv.FillRect(246+x*14, 150, 6, 180)
+		}
+		cv.Restore()
+
+		// Draw images
+		cv.DrawImage("cat.jpg", 480, 40, 320, 265)
+
+		// Draw text
+		cv.SetFont("Righteous-Regular.ttf", 40)
+		cv.FillText("<-- Cat", 820, 180)
+	})
+}