Merge pull request #67 from stanim/text

Fix text alignment

draw2dpdf/gc.go

@@ -138,10 +138,21 @@ func (gc *GraphicContext) GetDPI() int {
 }
 
 // GetStringBounds returns the approximate pixel bounds of the string s at x, y.
+// The left edge of the em square of the first character of s
+// and the baseline intersect at 0, 0 in the returned coordinates.
+// Therefore the top and left coordinates may well be negative.
 func (gc *GraphicContext) GetStringBounds(s string) (left, top, right, bottom float64) {
 	_, h := gc.pdf.GetFontSize()
+	d := gc.pdf.GetFontDesc("", "")
+	if d.Ascent == 0 {
+		// not defined (standard font?), use average of 81%
+		top = 0.81 * h
+	} else {
+		top = -float64(d.Ascent) * h / float64(d.Ascent-d.Descent)
+	}
+	bottom = top + h
 	margin := gc.pdf.GetCellMargin()
-	return margin, -h, margin + gc.pdf.GetStringWidth(s), 0
+	return -margin, top, -margin + gc.pdf.GetStringWidth(s), bottom
 }
 
 // CreateStringPath creates a path from the string s at x, y, and returns the string width.
@@ -151,8 +162,7 @@ func (gc *GraphicContext) CreateStringPath(text string, x, y float64) (cursor fl
 	w := right - left
 	h := bottom - top
 	// gc.pdf.SetXY(x, y-h) do not use this as y-h might be negative
-	margin := gc.pdf.GetCellMargin()
-	gc.pdf.MoveTo(x-margin, y-margin-0.82*h)
+	gc.pdf.MoveTo(x+left, y+top)
 	gc.pdf.CellFormat(w, h, text, "", 0, "BL", false, 0, "")
 	return w
 }

image.go

@@ -204,7 +204,7 @@ func (gc *ImageGraphicContext) CreateStringPath(s string, x, y float64) float64
 }
 
 // GetStringBounds returns the approximate pixel bounds of the string s at x, y.
-// The the left edge of the em square of the first character of s
+// The left edge of the em square of the first character of s
 // and the baseline intersect at 0, 0 in the returned coordinates.
 // Therefore the top and left coordinates may well be negative.
 func (gc *ImageGraphicContext) GetStringBounds(s string) (left, top, right, bottom float64) {

samples/helloworld/helloworld.go

@@ -41,6 +41,11 @@ func Draw(gc draw2d.GraphicContext, text string) {
 	gc.SetDPI(72)
 	gc.SetFontSize(14)
 	// Display Hello World
+	gc.SetStrokeColor(color.NRGBA{0x33, 0xFF, 0x33, 0xFF})
+	gc.MoveTo(8, 0)
+	gc.LineTo(8, 52)
+	gc.LineTo(297, 52)
+	gc.Stroke()
 	gc.FillString(text)
 	gc.FillStringAt(text, 8, 52)