default fill/stoke (black on white)

context.go

@@ -44,6 +44,11 @@ const (
 	AlignRight
 )
 
+var (
+	defaultFillStyle   = NewSolidPattern(color.White)
+	defaultStrokeStyle = NewSolidPattern(color.Black)
+)
+
 type Context struct {
 	width         int
 	height        int
@@ -88,6 +93,8 @@ func NewContextForRGBA(im *image.RGBA) *Context {
 		height:        im.Bounds().Size().Y,
 		im:            im,
 		color:         color.Transparent,
+		fillPattern:   defaultFillStyle,
+		strokePattern: defaultStrokeStyle,
 		lineWidth:     1,
 		fillRule:      FillRuleWinding,
 		fontFace:      basicfont.Face7x13,
@@ -182,6 +189,10 @@ func (dc *Context) setFillAndStrokeColor(c color.Color) {
 
 // SetFillStyle sets current fill style
 func (dc *Context) SetFillStyle(pattern Pattern) {
+	// if pattern is SolidPattern, also change dc.color(for dc.Clear, dc.drawString)
+	if fillStyle, ok := pattern.(*solidPattern); ok {
+		dc.color = fillStyle.color
+	}
 	dc.fillPattern = pattern
 }
 
@@ -190,7 +201,7 @@ func (dc *Context) SetStrokeStyle(pattern Pattern) {
 	dc.strokePattern = pattern
 }
 
-// SetColor sets the current color.
+// SetColor sets the current color(for both fill and stroke).
 func (dc *Context) SetColor(c color.Color) {
 	dc.setFillAndStrokeColor(c)
 }