lake heightmap fixes

go.mod

@@ -5,12 +5,14 @@ go 1.25.6
 require (
 	fyne.io/fyne/v2 v2.7.2
 	github.com/aquilax/go-perlin v1.1.0
+	github.com/ojrac/opensimplex-go v1.0.2
 )
 
 require (
 	fyne.io/systray v1.12.0 // indirect
 	github.com/BurntSushi/toml v1.5.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/disintegration/imaging v1.6.2 // indirect
 	github.com/fredbi/uri v1.1.1 // indirect
 	github.com/fsnotify/fsnotify v1.9.0 // indirect
 	github.com/fyne-io/gl-js v0.2.0 // indirect
@@ -29,7 +31,6 @@ require (
 	github.com/kr/text v0.2.0 // indirect
 	github.com/nfnt/resize v0.0.0-20180221191011-83c6a9932646 // indirect
 	github.com/nicksnyder/go-i18n/v2 v2.5.1 // indirect
-	github.com/ojrac/opensimplex-go v1.0.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/rymdport/portal v0.4.2 // indirect
 	github.com/srwiley/oksvg v0.0.0-20221011165216-be6e8873101c // indirect

go.sum

@@ -9,6 +9,8 @@ github.com/aquilax/go-perlin v1.1.0/go.mod h1:z9Rl7EM4BZY0Ikp2fEN1I5mKSOJ26HQpk0
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/disintegration/imaging v1.6.2 h1:w1LecBlG2Lnp8B3jk5zSuNqd7b4DXhcjwek1ei82L+c=
+github.com/disintegration/imaging v1.6.2/go.mod h1:44/5580QXChDfwIclfc/PCwrr44amcmDAg8hxG0Ewe4=
 github.com/felixge/fgprof v0.9.3 h1:VvyZxILNuCiUCSXtPtYmmtGvb65nqXh2QFWc0Wpf2/g=
 github.com/felixge/fgprof v0.9.3/go.mod h1:RdbpDgzqYVh/T9fPELJyV7EYJuHB55UTEULNun8eiPw=
 github.com/fredbi/uri v1.1.1 h1:xZHJC08GZNIUhbP5ImTHnt5Ya0T8FI2VAwI/37kh2Ko=
@@ -69,12 +71,14 @@ github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 github.com/yuin/goldmark v1.7.8 h1:iERMLn0/QJeHFhxSt3p6PeN9mGnvIKSpG9YYorDMnic=
 github.com/yuin/goldmark v1.7.8/go.mod h1:uzxRWxtg69N339t3louHJ7+O03ezfj6PlliRlaOzY1E=
+golang.org/x/image v0.0.0-20191009234506-e7c1f5e7dbb8/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
 golang.org/x/image v0.24.0 h1:AN7zRgVsbvmTfNyqIbbOraYL8mSwcKncEj8ofjgzcMQ=
 golang.org/x/image v0.24.0/go.mod h1:4b/ITuLfqYq1hqZcjofwctIhi7sZh2WaCjvsBNjjya8=
 golang.org/x/net v0.35.0 h1:T5GQRQb2y08kTAByq9L4/bz8cipCdA8FbRTXewonqY8=
 golang.org/x/net v0.35.0/go.mod h1:EglIi67kWsHKlRzzVMUD93VMSWGFOMSZgxFjparz1Qk=
 golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
 golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.22.0 h1:bofq7m3/HAFvbF51jz3Q9wLg3jkvSPuiZu/pD1XwgtM=
 golang.org/x/text v0.22.0/go.mod h1:YRoo4H8PVmsu+E3Ou7cqLVH8oXWIHVoX0jqUWALQhfY=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

terrain.go

@@ -8,6 +8,7 @@ import (
 	"math"
 	"math/rand"
 
+	"github.com/disintegration/imaging"
 	"github.com/ojrac/opensimplex-go"
 )
 
@@ -176,28 +177,23 @@ func GenerateLakes(width, height, numLakes int, lakeSizeLower, lakeSizeUpper flo
 // DarkenLakeAreas applies a visual darkening effect to the heightmap where lakes exist.
 func DarkenLakeAreas(heightmap image.Image, lakePixels []image.Point) image.Image {
 	bounds := heightmap.Bounds()
+	width := bounds.Dx()
+
+	// Create a new black image to draw the lakes on
+	lakeMask := image.NewRGBA(bounds)
+	black := color.RGBA{0, 0, 0, 255}
+	for _, p := range lakePixels {
+		lakeMask.Set(p.X, p.Y, black)
+	}
+
+	// Apply a Gaussian blur to the lake mask
+	blurRadius := float64(width) * 0.05
+	blurredLakeMask := imaging.Blur(lakeMask, blurRadius)
+
+	// Composite the blurred lake mask onto the heightmap with 50% opacity
 	composite := image.NewRGBA(bounds)
 	draw.Draw(composite, bounds, heightmap, image.Point{}, draw.Src)
-
+	draw.DrawMask(composite, bounds, blurredLakeMask, image.Point{}, image.NewUniform(color.Alpha{192}), image.Point{}, draw.Over)
-	// Create a map for quick lookup of lake pixels
-	isLake := make(map[image.Point]bool)
-	for _, p := range lakePixels {
-		isLake[p] = true
-	}
-
-	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
-		for x := bounds.Min.X; x < bounds.Max.X; x++ {
-			if !isLake[image.Point{X: x, Y: y}] {
-				c := composite.At(x, y)
-				r, g, b, a := c.RGBA()
-				// Darken by 15%
-				r = uint32(float64(r) * 0.85)
-				g = uint32(float64(g) * 0.85)
-				b = uint32(float64(b) * 0.85)
-				composite.Set(x, y, color.RGBA64{R: uint16(r), G: uint16(g), B: uint16(b), A: uint16(a)})
-			}
-		}
-	}
 
 	return composite
 }