diff --git a/cmd/mtwebmapper/main.go b/cmd/mtwebmapper/main.go
index 69dc373..50fe0fb 100644
--- a/cmd/mtwebmapper/main.go
+++ b/cmd/mtwebmapper/main.go
@@ -24,25 +24,23 @@ import (
 
 func blowUp(src image.Image) *image.RGBA {
 
-	// TODO: Use fix point arithmetic, fast path for image.RGBA
+	// TODO: Fast path for image.RGBA
 
 	dst := image.NewRGBA(image.Rect(0, 0, 256, 256))
 
-	sw, sh := src.Bounds().Dx(), src.Bounds().Dy()
+    // fix point numbers x:8
+	dx, dy := src.Bounds().Dx(), src.Bounds().Dy()
 
-	dx := float32(sw) / float32(256)
-	dy := float32(sh) / float32(256)
+	bx, by := src.Bounds().Min.X<<8, src.Bounds().Min.Y<<8
 
-	bx, by := src.Bounds().Min.X, src.Bounds().Min.Y
-
-	py := float32(by)
+	py := by
 	for y := 0; y < 256; y++ {
-		sy := int(py)
+		sy := (py >> 8) & 0xff
 		ox := -1
-		px := float32(bx)
+		px := bx
 		var col color.Color
 		for x := 0; x < 256; x++ {
-			sx := int(px)
+			sx := (px >> 8) & 0xff
 			if sx != ox { // Minimize interface indirection access.
 				ox = sx
 				col = src.At(sx, sy)