p68: 512×384 整图离线渲染截图证据

- MapSnapshot：MapGen.Result 纯 CPU 渲染为整图 PNG（每瓦片 8px，自包含
  IHDR/IDAT/IEND + CRC32 + ZLibStream，无外部图像依赖）；调色板覆盖
  河流/主路/农田/民居屋顶/小径/桥/树丛
- Program.fs：LV_P68_MAPSHOT=1 钩子用 paramsForSize 512 384 seed=4242 生成并
  离线渲染整图后退出（headless，不需图形设备）
- P68MapSnapshotTests（3 例，红先）：尺寸/PNG 签名、要素像素存在、两次渲染逐字节一致
- scripts/analyze-p68.py：尺寸/调色板像素/无黑白大块/missing_glyph_slots=0/确定性
- Desktop 336/336、Kernel 119/119；digest 953775FA…7F6C ×3 PASS；未动 Kernel/Sim

1 files changed, 54 insertions, 0 deletions

diff --git a/src/LivingVillage.Desktop.Tests/P68MapSnapshotTests.fs b/src/LivingVillage.Desktop.Tests/P68MapSnapshotTests.fs
new file mode 100644
index 0000000..4109aae
--- /dev/null
+++ b/src/LivingVillage.Desktop.Tests/P68MapSnapshotTests.fs
@@ -0,0 +1,54 @@
+namespace LivingVillage.Desktop.Tests
+
+open Microsoft.VisualStudio.TestTools.UnitTesting
+open LivingVillage.Desktop
+
+/// P68：512×384 整图离线渲染（MapSnapshot）的可验收护栏。
+/// 断言尺寸/要素像素存在性/确定性；调色板口径与 scripts/analyze-p68.py 一致。
+[<TestClass>]
+type P68MapSnapshotTests () =
+
+    let map = MapGen.generateWithSize 512 384 (uint64 4242)
+
+    let be32 (bytes: byte array) (offset: int) : int =
+        (int bytes.[offset] <<< 24)
+        ||| (int bytes.[offset + 1] <<< 16)
+        ||| (int bytes.[offset + 2] <<< 8)
+        ||| int bytes.[offset + 3]
+
+    let countColor (rgb: byte array) (color: byte * byte * byte) : int =
+        let r, g, b = color
+        let mutable count = 0
+        let mutable i = 0
+        while i < rgb.Length do
+            if rgb.[i] = r && rgb.[i + 1] = g && rgb.[i + 2] = b then count <- count + 1
+            i <- i + 3
+        count
+
+    [<TestMethod>]
+    member _.RenderPngHasFullMapDimensions () =
+        let png = MapSnapshot.renderPng map 4
+        let signature = [| 137uy; 80uy; 78uy; 71uy; 13uy; 10uy; 26uy; 10uy |]
+        CollectionAssert.AreEqual(signature, png.[0..7])
+        Assert.AreEqual<string>("IHDR", System.Text.Encoding.ASCII.GetString(png.[12..15]))
+        Assert.AreEqual<int>(512 * 4, be32 png 16)
+        Assert.AreEqual<int>(384 * 4, be32 png 20)
+
+    [<TestMethod>]
+    member _.RenderRgbContainsRiverRoadFarmAndBuildingPixels () =
+        let rgb = MapSnapshot.renderRgb map 8
+        Assert.AreEqual<int>(512 * 8 * 384 * 8 * 3, rgb.Length)
+        Assert.IsTrue(countColor rgb (52uy, 110uy, 180uy) > 0, "river (water) pixels missing")
+        Assert.IsTrue(
+            countColor rgb (120uy, 168uy, 84uy) + countColor rgb (154uy, 186uy, 96uy) > 0,
+            "farmland pixels missing")
+        Assert.IsTrue(countColor rgb (214uy, 190uy, 128uy) > 0, "main-road pixels missing")
+        Assert.IsTrue(countColor rgb (196uy, 176uy, 120uy) > 0, "path pixels missing")
+        Assert.IsTrue(countColor rgb (58uy, 58uy, 70uy) > 0, "building roof pixels missing")
+
+    [<TestMethod>]
+    member _.RenderIsByteIdenticalAcrossRuns () =
+        let first = MapSnapshot.renderPng map 8
+        let second = MapSnapshot.renderPng (MapGen.generateWithSize 512 384 (uint64 4242)) 8
+        CollectionAssert.AreEqual(first, second)
+        Assert.IsTrue(MapSnapshot.renderPng map 4 <> first, "different scale must produce a different image")