added opacity to mark squares

notnil · Nov 25, 2024 · f036e3b · f036e3b
1 parent b30c702
commit f036e3b
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Showing 3 changed files with 11 additions and 9 deletions.
diff --git a/image/README.md b/image/README.md
@@ -24,8 +24,8 @@ image.SVG(file, pos.Board())
 The default colors, shown in the example SVG below, are (235, 209, 166) for light squares and (165, 117, 81) for dark squares.  The light and dark squares can be customized using the SquareColors() option. 
 
 ```go
-white := color.RGBA{255, 255, 255, 1}
-gray := color.RGBA{120, 120, 120, 1}
+white := color.RGBA{255, 255, 255, 255}
+gray := color.RGBA{120, 120, 120, 255}
 sqrs := image.SquareColors(white, gray)
 image.SVG(file, pos.Board(), sqrs)
 ```
@@ -35,7 +35,7 @@ image.SVG(file, pos.Board(), sqrs)
 MarkSquares is designed to be used as an optional argument to the SVG function.  It marks the given squares with the color.  A possible usage includes marking squares of the previous move.
 
 ```go
-yellow := color.RGBA{255, 255, 0, 1}
+yellow := color.RGBA{255, 255, 0, 51}
 mark := image.MarkSquares(yellow, chess.D2, chess.D4)
 image.SVG(file, pos.Board(), mark)
 ```
@@ -82,7 +82,7 @@ func main() {
     }
 
     // write board SVG to file
-    yellow := color.RGBA{255, 255, 0, 1}
+    yellow := color.RGBA{255, 255, 0, 51}
     mark := image.MarkSquares(yellow, chess.D2, chess.D4)
     arrows := image.MarkArrows(image.Arrow(chess.D2, chess.D4))
     if err := image.SVG(f, pos.Board(), mark, arrows); err != nil {

diff --git a/image/image.go b/image/image.go
@@ -152,7 +152,9 @@ func (e *Encoder) EncodeSVG(b *chess.Board) error {
 			canvas.Rect(x, y, sqWidth, sqHeight, "fill: "+colorToHex(c))
 			markColor, ok := e.marks[sq]
 			if ok {
-				canvas.Rect(x, y, sqWidth, sqHeight, "fill-opacity:0.2;fill: "+colorToHex(markColor))
+				_, _, _, a := markColor.RGBA()
+				opacity := float64(a) / 0xffff
+				canvas.Rect(x, y, sqWidth, sqHeight, fmt.Sprintf("fill-opacity:%f;fill: %s", opacity, colorToHex(markColor)))
 			}
 			// draw piece
 			p := boardMap[sq]

diff --git a/image/image_test.go b/image/image_test.go
@@ -12,8 +12,8 @@ import (
 	"github.com/notnil/chess/image"
 )
 
-const expectedMD5 = "a2ee66ca19e4c347aec41371c1ca07f8"
-const expectedMD5Black = "ce4d4e033a50678898c62928b8e0a15c"
+const expectedMD5 = "625c63ef80796a3485004952a18c9b25"
+const expectedMD5Black = "1988104209a5401be2f645967fadec78"
 const expectedMD5KnightsAndDiagonalArrows = "9c95aa56cec67be2ceee141f259753f7"
 
 func TestSVG(t *testing.T) {
@@ -24,7 +24,7 @@ func TestSVG(t *testing.T) {
 	if err := pos.UnmarshalText([]byte(fenStr)); err != nil {
 		t.Error(err)
 	}
-	mark := image.MarkSquares(color.RGBA{255, 255, 0, 1}, chess.D2, chess.D4)
+	mark := image.MarkSquares(color.RGBA{255, 255, 0, 100}, chess.D2, chess.D4)
 	arrows := image.MarkArrows(image.Arrow(chess.D2, chess.D4))
 	if err := image.SVG(buf, pos.Board(), mark, arrows); err != nil {
 		t.Error(err)
@@ -46,7 +46,7 @@ func TestSVGFromBlack(t *testing.T) {
 	if err := pos.UnmarshalText([]byte(fenStr)); err != nil {
 		t.Error(err)
 	}
-	mark := image.MarkSquares(color.RGBA{255, 255, 0, 1}, chess.D2, chess.D4)
+	mark := image.MarkSquares(color.RGBA{255, 255, 0, 51}, chess.D2, chess.D4)
 	arrows := image.MarkArrows(image.Arrow(chess.D2, chess.D4).WithColor(color.Black))
 	per := image.Perspective(chess.Black)
 	if err := image.SVG(buf, pos.Board(), mark, arrows, per); err != nil {