Update stitcher README.md and flag usage string

#7

Author: Dadido3

bin/stitch/README.md

@@ -43,6 +43,7 @@ example list of files:
     The path to the player-path.json file. This contains the tracked path of the player. Defaults to "./../../output/player-path.json".
   - `output string`
     The path and filename of the resulting stitched image. Defaults to "output.png".
+    Supported formats/file extensions: `.png`, `.jpg`, `.dzi`.
   - `xmax int`
     Right bound of the output rectangle. This coordinate is not included in the output.
   - `xmin int`
@@ -58,6 +59,12 @@ To output the 100x100 area that is centered at the origin use:
 ./stitch -divide 1 -xmin -50 -xmax 50 -ymin -50 -ymax 50
 ```
 
+To output a [Deep Zoom Image (DZI)](https://en.wikipedia.org/wiki/Deep_Zoom), which can be used with [OpenSeadragon](https://openseadragon.github.io/examples/tilesource-dzi/), use:
+
+``` Shell Session
+./stitch -output capture.dzi
+```
+
 To start the program interactively:
 
 ``` Shell Session

bin/stitch/main.go

@@ -22,7 +22,7 @@ import (
 var flagInputPath = flag.String("input", filepath.Join(".", "..", "..", "output"), "The source path of the image tiles to be stitched.")
 var flagEntitiesInputPath = flag.String("entities", filepath.Join(".", "..", "..", "output", "entities.json"), "The path to the entities.json file.")
 var flagPlayerPathInputPath = flag.String("player-path", filepath.Join(".", "..", "..", "output", "player-path.json"), "The path to the player-path.json file.")
-var flagOutputPath = flag.String("output", filepath.Join(".", "output.png"), "The path and filename of the resulting stitched image.")
+var flagOutputPath = flag.String("output", filepath.Join(".", "output.png"), "The path and filename of the resulting stitched image. Supported formats/file extensions: `.png`, `.jpg`, `.dzi`.")
 var flagScaleDivider = flag.Int("divide", 1, "A downscaling factor. 2 will produce an image with half the side lengths.")
 var flagBlendTileLimit = flag.Int("blend-tile-limit", 9, "Limits median blending to the n newest tiles by file modification time. If set to 0, all available tiles will be median blended.")
 var flagXMin = flag.Int("xmin", 0, "Left bound of the output rectangle. This coordinate is included in the output.")