6 files changed, 10 insertions, 4 deletions
diff --git a/go.mod b/go.mod
index b2c2c0c..2ac2eb3 100644
--- a/go.mod
+++ b/go.mod
@@ -7,5 +7,5 @@ require (
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 // indirect
 	github.com/wcharczuk/go-chart v2.0.2-0.20191206192251-962b9abdec2b+incompatible
 	golang.org/x/image v0.0.0-20200618115811-c13761719519 // indirect
-	rescribe.xyz/integralimg v0.2.1
+	rescribe.xyz/integralimg v0.3.0
 )
diff --git a/go.sum b/go.sum
index d1d33ca..42e324b 100644
--- a/go.sum
+++ b/go.sum
@@ -16,5 +16,5 @@ golang.org/x/net v0.0.0-20181201002055-351d144fa1fc/go.mod h1:mL1N/T3taQHkDXs73r
 golang.org/x/oauth2 v0.0.0-20181203162652-d668ce993890/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/tools v0.0.0-20181205014116-22934f0fdb62/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-rescribe.xyz/integralimg v0.2.1 h1:OhYifujtlVGYm/WfLl8ios/bouzIWcwuzbRyCZQiab0=
-rescribe.xyz/integralimg v0.2.1/go.mod h1:2euyPigpyIixTWO6JtFEhDp/3YKA6yy+d8g17oL0L0s=
+rescribe.xyz/integralimg v0.3.0 h1:G5/yR8jKtewLlCEkygg7T8h1nllwNt4SmLdw+1fCsE4=
+rescribe.xyz/integralimg v0.3.0/go.mod h1:2euyPigpyIixTWO6JtFEhDp/3YKA6yy+d8g17oL0L0s=
diff --git a/sauvola.go b/sauvola.go
index 9eef01b..49181de 100644
--- a/sauvola.go
+++ b/sauvola.go
@@ -61,7 +61,8 @@ func PreCalcedSauvola(intImg integralimg.Image, intSqImg integralimg.SqImage, im
 
 	for y := b.Min.Y; y < b.Max.Y; y++ {
 		for x := b.Min.X; x < b.Max.X; x++ {
-			m, dev := integralimg.MeanStdDevWindow(intImg, intSqImg, x, y, windowsize)
+			r := centeredRectangle(x, y, windowsize)
+			m, dev := integralimg.MeanStdDev(intImg, intSqImg, r)
 			// Divide by 255 to adjust from Gray16 used by integralimg to 8 bit Gray
 			m8 := m / 255
 			dev8 := dev / 255
@@ -76,3 +77,8 @@ func PreCalcedSauvola(intImg integralimg.Image, intSqImg integralimg.SqImage, im
 
 	return new
 }
+
+func centeredRectangle(x, y, size int) image.Rectangle {
+	step := size / 2
+	return image.Rect(x - step - 1, y - step - 1, x + step, y + step)
+}
diff --git a/testdata/pg1_integralsauvola_k0.3_w19.png b/testdata/pg1_integralsauvola_k0.3_w19.png
index 00aa1d8..a648969 100644
--- a/testdata/pg1_integralsauvola_k0.3_w19.png
+++ b/testdata/pg1_integralsauvola_k0.3_w19.png
diff --git a/testdata/pg1_integralsauvola_k0.5_w19.png b/testdata/pg1_integralsauvola_k0.5_w19.png
index 77a7194..86c0104 100644
--- a/testdata/pg1_integralsauvola_k0.5_w19.png
+++ b/testdata/pg1_integralsauvola_k0.5_w19.png
diff --git a/testdata/pg1_integralsauvola_k0.5_w41.png b/testdata/pg1_integralsauvola_k0.5_w41.png
index 5ddc854..5b003f1 100644
--- a/testdata/pg1_integralsauvola_k0.5_w41.png
+++ b/testdata/pg1_integralsauvola_k0.5_w41.png