Add first sketch of Deep Zoom Image exporter

bin/stitch/dzi.go

@@ -0,0 +1,153 @@
+// Copyright (c) 2023 David Vogel
+//
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"image"
+	"log"
+	"os"
+	"path/filepath"
+	"strconv"
+	"sync"
+	"time"
+)
+
+const (
+	dziTileSize = 512 // The (maximum) width and height of a tile in pixels, not including the overlap.
+	dziOverlap  = 1   // The amount of additional pixels on every side of every tile. The real (max) width/height of an image is `2*overlap + tileSize`.
+)
+
+type DZI struct {
+	stitchedImage *StitchedImage
+
+	fileExtension string
+
+	tileSize int // The (maximum) width and height of a tile in pixels, not including the overlap.
+	overlap  int // The amount of additional pixels on every side of every tile. The real (max) width/height of an image is `2*overlap + tileSize`.
+
+	maxZoomLevel int // The maximum zoom level that is needed.
+}
+
+func NewDZI(stitchedImage *StitchedImage) DZI {
+	dzi := DZI{
+		stitchedImage: stitchedImage,
+
+		fileExtension: ".png",
+
+		overlap:  dziOverlap,
+		tileSize: dziTileSize,
+	}
+
+	width, height := stitchedImage.bounds.Dx(), stitchedImage.bounds.Dy()
+
+	// Calculate max zoom level and stuff.
+	neededLength := max(width, height)
+	var sideLength int = 1
+	var level int
+	for sideLength < neededLength {
+		level += 1
+		sideLength *= 2
+	}
+	dzi.maxZoomLevel = level
+	//dzi.maxZoomLevelLength = sideLength
+
+	return dzi
+}
+
+// ExportDZIDescriptor exports the descriptive JSON file at the given path.
+func (d DZI) ExportDZIDescriptor(outputPath string) error {
+	log.Printf("Creating DZI descriptor %q.", outputPath)
+
+	f, err := os.Create(outputPath)
+	if err != nil {
+		return fmt.Errorf("failed to create file: %w", err)
+	}
+	defer f.Close()
+
+	// Prepare data that describes the layout of the image files.
+	var dziDescriptor struct {
+		Image struct {
+			XMLNS    string `json:"xmlns"`
+			Format   string
+			Overlap  string
+			TileSize string
+			Size     struct {
+				Width  string
+				Height string
+			}
+		}
+	}
+
+	dziDescriptor.Image.XMLNS = "http://schemas.microsoft.com/deepzoom/2008"
+	dziDescriptor.Image.Format = "png"
+	dziDescriptor.Image.Overlap = strconv.Itoa(d.overlap)
+	dziDescriptor.Image.TileSize = strconv.Itoa(d.tileSize)
+	dziDescriptor.Image.Size.Width = strconv.Itoa(d.stitchedImage.bounds.Dx())
+	dziDescriptor.Image.Size.Height = strconv.Itoa(d.stitchedImage.bounds.Dy())
+
+	jsonEnc := json.NewEncoder(f)
+	return jsonEnc.Encode(dziDescriptor)
+}
+
+// ExportDZITiles exports the single image tiles for every zoom level.
+func (d DZI) ExportDZITiles(outputDir string) error {
+	log.Printf("Creating DZI tiles in %q.", outputDir)
+
+	// Start with the highest zoom level (Where every world pixel is exactly mapped into one image pixel).
+	// Generate all tiles for this level, and then stitch another image (scaled down by a factor of 2) based on the previously generated tiles.
+	// Repeat this process until we have generated level 0.
+
+	// The current stitched image we are working with.
+	stitchedImage := d.stitchedImage
+
+	for zoomLevel := d.maxZoomLevel; zoomLevel >= 0; zoomLevel-- {
+
+		levelBasePath := filepath.Join(outputDir, fmt.Sprintf("%d", zoomLevel))
+		if err := os.Mkdir(levelBasePath, 0755); err != nil {
+			return fmt.Errorf("failed to create zoom level base directory %q: %w", levelBasePath, err)
+		}
+
+		// Store list of tiles, so that we can reuse them in the next step for the smaller zoom level.
+		imageTiles := ImageTiles{}
+
+		// Export tiles.
+		for iY := 0; iY <= (stitchedImage.bounds.Dy()-1)/d.tileSize; iY++ {
+			for iX := 0; iX <= (stitchedImage.bounds.Dx()-1)/d.tileSize; iX++ {
+				rect := image.Rect(iX*d.tileSize, iY*d.tileSize, iX*d.tileSize+d.tileSize, iY*d.tileSize+d.tileSize)
+				rect = rect.Add(stitchedImage.bounds.Min)
+				rect = rect.Inset(-d.overlap)
+				img := stitchedImage.SubStitchedImage(rect)
+				filePath := filepath.Join(levelBasePath, fmt.Sprintf("%d_%d%s", iX, iY, d.fileExtension))
+				if err := exportPNG(img, filePath); err != nil {
+					return fmt.Errorf("failed to export PNG: %w", err)
+				}
+
+				scaleDivider := 2
+				imageTiles = append(imageTiles, ImageTile{
+					fileName:         filePath,
+					modTime:          time.Now(),
+					scaleDivider:     scaleDivider,
+					image:            image.Rect(DivideFloor(img.Bounds().Min.X, scaleDivider), DivideFloor(img.Bounds().Min.Y, scaleDivider), DivideCeil(img.Bounds().Max.X, scaleDivider), DivideCeil(img.Bounds().Max.Y, scaleDivider)),
+					imageMutex:       &sync.RWMutex{},
+					invalidationChan: make(chan struct{}, 1),
+					timeoutChan:      make(chan struct{}, 1),
+				})
+			}
+		}
+
+		// Create new stitched image from the previously exported tiles.
+		// The tiles are already created in a way, that they are scaled down by a factor of 2.
+		var err error
+		stitchedImage, err = NewStitchedImage(imageTiles, imageTiles.Bounds(), BlendMethodMedian{BlendTileLimit: 0}, 128, nil)
+		if err != nil {
+			return fmt.Errorf("failed to run NewStitchedImage(): %w", err)
+		}
+	}
+
+	return nil
+}

bin/stitch/export-dzi.go

@@ -0,0 +1,38 @@
+// Copyright (c) 2023 David Vogel
+//
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+func exportDZI(stitchedImage *StitchedImage, outputPath string) error {
+	descriptorPath := outputPath
+	extension := filepath.Ext(outputPath)
+	outputTilesPath := strings.TrimSuffix(outputPath, extension) + "_files"
+
+	dzi := NewDZI(stitchedImage)
+
+	// Create base directory of all DZI files.
+	if err := os.MkdirAll(outputTilesPath, 0755); err != nil {
+		return fmt.Errorf("failed to create output directory: %w", err)
+	}
+
+	// Export DZI descriptor.
+	if err := dzi.ExportDZIDescriptor(descriptorPath); err != nil {
+		return fmt.Errorf("failed to export DZI descriptor: %w", err)
+	}
+
+	// Export DZI tiles.
+	if err := dzi.ExportDZITiles(outputTilesPath); err != nil {
+		return fmt.Errorf("failed to export DZI tiles: %w", err)
+	}
+
+	return nil
+}

bin/stitch/main.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2019-2022 David Vogel
+// Copyright (c) 2019-2023 David Vogel
 //
 // This software is released under the MIT License.
 // https://opensource.org/licenses/MIT
@@ -276,6 +276,10 @@ func main() {
 		if err := exportJPEG(stitchedImage, *flagOutputPath); err != nil {
 			log.Panicf("Export of JPEG file failed: %v", err)
 		}
+	case ".dzi":
+		if err := exportDZI(stitchedImage, *flagOutputPath); err != nil {
+			log.Panicf("Export of DZI file failed: %v", err)
+		}
 	default:
 		log.Panicf("Unknown output format %q.", fileExtension)
 	}