doc: Update examples/hsv

docs/examples/hsv.html

@@ -49,7 +49,10 @@ var (
         hueInt        = 0
         saturationInt = 128
         valueInt      = 128
-        gophersImage  *ebiten.Image
+        inverted      = false
+
+        prevPressedI = false
+        gophersImage *ebiten.Image
 )
 
 func clamp(v, min, max int) int {
@@ -84,6 +87,13 @@ func update(screen *ebiten.Image) error {
         if ebiten.IsKeyPressed(ebiten.KeyX) {
                 valueInt++
         }
+
+        pressedI := ebiten.IsKeyPressed(ebiten.KeyI)
+        if pressedI && !prevPressedI {
+                inverted = !inverted
+        }
+        prevPressedI = pressedI
+
         if ebiten.IsRunningSlowly() {
                 return nil
         }
@@ -94,15 +104,26 @@ func update(screen *ebiten.Image) error {
         w, h := gophersImage.Size()
         op := &ebiten.DrawImageOptions{}
         op.GeoM.Translate(float64(screenWidth-w)/2, float64(screenHeight-h)/2)
+
         hue := float64(hueInt) * 2 * math.Pi / 128
         saturation := float64(saturationInt) / 128
         value := float64(valueInt) / 128
         op.ColorM.ChangeHSV(hue, saturation, value)
+        if inverted {
+                op.ColorM.Scale(-1, -1, -1, 1)
+                op.ColorM.Translate(1, 1, 1, 0)
+        }
+
         screen.DrawImage(gophersImage, op)
 
+        msgInverted := "false"
+        if inverted {
+                msgInverted = "true"
+        }
         msg := fmt.Sprintf(`Hue:        %0.2f [Q][W]
 Saturation: %0.2f [A][S]
-Value:      %0.2f [Z][X]`, hue, saturation, value)
+Value:      %0.2f [Z][X]
+Inverted:   %s [I]`, hue, saturation, value, msgInverted)
         ebitenutil.DebugPrint(screen, msg)
         return nil
 }