Add reusable DZI tile generator script

scripts/generate-dzi.cs

@@ -0,0 +1,161 @@
+#!/usr/bin/env dotnet-script
+// Deep Zoom Image (DZI) tile generator
+// Usage: dotnet run scripts/generate-dzi.cs -- <input-image> <output-dir> [options]
+//
+// Options:
+//   --tile-size <n>   Tile size in pixels (default: 256)
+//   --overlap <n>     Tile overlap in pixels (default: 1)
+//   --format <ext>    Output tile format: png or jpg (default: png)
+//   --quality <n>     JPEG quality 1-100, only used for jpg (default: 90)
+//
+// Example:
+//   dotnet run scripts/generate-dzi.cs -- myimage.png output/ --tile-size 256 --overlap 1
+
+#:package SkiaSharp@3.119.1
+
+using System;
+using System.IO;
+using SkiaSharp;
+
+// ── Parse arguments ──────────────────────────────────────────────────────────
+
+string? inputPath = null;
+string? outputDir = null;
+int tileSize = 256;
+int overlap = 1;
+string format = "png";
+int jpegQuality = 90;
+
+for (int i = 0; i < args.Length; i++)
+{
+    switch (args[i])
+    {
+        case "--tile-size": tileSize   = int.Parse(args[++i]); break;
+        case "--overlap":   overlap    = int.Parse(args[++i]); break;
+        case "--format":    format     = args[++i].ToLowerInvariant(); break;
+        case "--quality":   jpegQuality = int.Parse(args[++i]); break;
+        default:
+            if (inputPath is null)  inputPath  = args[i];
+            else if (outputDir is null) outputDir = args[i];
+            else { Console.Error.WriteLine($"Unknown argument: {args[i]}"); Environment.Exit(1); }
+            break;
+    }
+}
+
+if (inputPath is null || outputDir is null)
+{
+    Console.Error.WriteLine("Usage: dotnet run scripts/generate-dzi.cs -- <input-image> <output-dir> [--tile-size 256] [--overlap 1] [--format png|jpg] [--quality 90]");
+    Environment.Exit(1);
+}
+
+if (format != "png" && format != "jpg")
+{
+    Console.Error.WriteLine("--format must be 'png' or 'jpg'");
+    Environment.Exit(1);
+}
+
+// ── Load source image ─────────────────────────────────────────────────────────
+
+Console.WriteLine($"Loading {inputPath}…");
+using var srcStream = File.OpenRead(inputPath);
+using var srcBitmap = SKBitmap.Decode(srcStream);
+if (srcBitmap is null)
+{
+    Console.Error.WriteLine($"Failed to decode image: {inputPath}");
+    Environment.Exit(1);
+}
+
+int imageWidth  = srcBitmap.Width;
+int imageHeight = srcBitmap.Height;
+int maxLevel    = (int)Math.Ceiling(Math.Log2(Math.Max(imageWidth, imageHeight)));
+
+Console.WriteLine($"Image: {imageWidth}×{imageHeight}, max level: {maxLevel}, tile size: {tileSize}, overlap: {overlap}, format: {format}");
+
+// ── Prepare output directories ────────────────────────────────────────────────
+
+string baseName  = Path.GetFileNameWithoutExtension(outputDir.TrimEnd('/', '\\'));
+// If outputDir itself ends with the image name, use it directly; otherwise create a subdir.
+string dziPath   = outputDir.EndsWith(".dzi", StringComparison.OrdinalIgnoreCase)
+    ? outputDir
+    : Path.Combine(outputDir, baseName + ".dzi");
+
+// Derive tile directory from DZI path: same name with _files suffix
+string tileRoot  = Path.Combine(Path.GetDirectoryName(dziPath)!, Path.GetFileNameWithoutExtension(dziPath) + "_files");
+
+Directory.CreateDirectory(Path.GetDirectoryName(dziPath)!);
+
+// ── Generate tiles level by level ─────────────────────────────────────────────
+
+var encodeFormat  = format == "jpg" ? SKEncodedImageFormat.Jpeg : SKEncodedImageFormat.Png;
+var fileExtension = format == "jpg" ? "jpg" : "png";
+
+for (int level = 0; level <= maxLevel; level++)
+{
+    int scale      = maxLevel - level;
+    int levelWidth  = Math.Max(1, (int)Math.Ceiling(imageWidth  / Math.Pow(2, scale)));
+    int levelHeight = Math.Max(1, (int)Math.Ceiling(imageHeight / Math.Pow(2, scale)));
+
+    string levelDir = Path.Combine(tileRoot, level.ToString());
+    Directory.CreateDirectory(levelDir);
+
+    // Scale source image to level dimensions
+    using var levelBitmap = new SKBitmap(levelWidth, levelHeight, SKColorType.Rgba8888, SKAlphaType.Premul);
+    using (var canvas = new SKCanvas(levelBitmap))
+    {
+        canvas.Clear(SKColors.Transparent);
+        var dest = new SKRect(0, 0, levelWidth, levelHeight);
+        var src  = new SKRect(0, 0, imageWidth, imageHeight);
+        using var paint = new SKPaint { IsAntialias = true };
+        canvas.DrawBitmap(srcBitmap, src, dest, paint);
+    }
+
+    int cols = (int)Math.Ceiling((double)levelWidth  / tileSize);
+    int rows = (int)Math.Ceiling((double)levelHeight / tileSize);
+    int tileCount = cols * rows;
+
+    Console.Write($"  Level {level,2}: {levelWidth,6}×{levelHeight,-6}  {cols}×{rows} tiles… ");
+
+    for (int col = 0; col < cols; col++)
+    {
+        for (int row = 0; row < rows; row++)
+        {
+            // Tile origin in the level image (without overlap)
+            int tileX = col * tileSize;
+            int tileY = row * tileSize;
+
+            // Extend by overlap on each side (clamped to image bounds)
+            int srcX = Math.Max(0, tileX - overlap);
+            int srcY = Math.Max(0, tileY - overlap);
+            int srcRight  = Math.Min(levelWidth,  tileX + tileSize + overlap);
+            int srcBottom = Math.Min(levelHeight, tileY + tileSize + overlap);
+            int srcW = srcRight  - srcX;
+            int srcH = srcBottom - srcY;
+
+            // Extract the tile region
+            using var tileBitmap = new SKBitmap(srcW, srcH, SKColorType.Rgba8888, SKAlphaType.Premul);
+            levelBitmap.ExtractSubset(tileBitmap, new SKRectI(srcX, srcY, srcRight, srcBottom));
+
+            string tilePath = Path.Combine(levelDir, $"{col}_{row}.{fileExtension}");
+            using var fs = File.Create(tilePath);
+            tileBitmap.Encode(fs, encodeFormat, jpegQuality);
+        }
+    }
+
+    Console.WriteLine("done");
+}
+
+// ── Write DZI descriptor ──────────────────────────────────────────────────────
+
+var dziContent = $"""
+    <?xml version="1.0" encoding="UTF-8"?>
+    <Image xmlns="http://schemas.microsoft.com/deepzoom/2008"
+           Format="{fileExtension}" Overlap="{overlap}" TileSize="{tileSize}">
+      <Size Width="{imageWidth}" Height="{imageHeight}"/>
+    </Image>
+    """;
+
+File.WriteAllText(dziPath, dziContent, System.Text.Encoding.UTF8);
+
+Console.WriteLine($"\nWrote DZI: {dziPath}");
+Console.WriteLine($"Tiles:     {tileRoot}");
+Console.WriteLine("Done.");