Update README.md

Author: Marko Ljubicic

README.md

@@ -1,3 +1,52 @@
+## Image Tags Updater
+
+This app updates JPEG metadata from the first sheet of an XLSX file and supports flexible column headers.
+
+### Required and Optional Columns
+
+- Required (one of):
+  - `Source file name` or `source` — matched to uploaded image filenames (case-insensitive, trimmed)
+- Optional:
+  - `Output file name` or `ouput` — desired output name; `.jpg` is added if missing
+  - `Title` or `title`
+  - `Caption` or `caption`
+  - `Description` or `description`
+  - `Keywords` or `keywords`
+
+Aliases are case-insensitive and whitespace around headers is ignored.
+
+### Matching Logic
+
+- Images are matched to rows by `Source file name` (or `source`) after converting both to lowercase and trimming.
+- If no row is found, the image shows `No matching row in XLSX`.
+
+### Metadata Writing
+
+- `Title`, `Caption`, `Keywords`: stored as Unicode in EXIF XP tags (`XPTitle`, `XPComment`, `XPKeywords`).
+- `Description`: written to `XPComment` for Unicode; `ImageDescription` is ASCII-only, so non-ASCII text is transliterated (Serbian mappings: Š→S, Đ→DJ, Č→C, Ć→C, Ž→Z, DŽ→DZ; lowercase equivalents too).
+- `Keywords`: written as a single string; if you separate by commas/semicolons, they are kept as typed.
+
+### Output Filename
+
+- Uses `Output file name` (or `ouput`) if provided; otherwise original image name.
+- Ensures `.jpg`/`.jpeg` extension; adds `.jpg` if missing.
+- Applies the same transliteration for Serbian characters to keep ASCII-safe names.
+
+### Example (first rows)
+
+| Source file name | Output file name | Title        | Caption          | Description        | Keywords        |
+| ---------------- | ---------------- | ------------ | ---------------- | ------------------ | --------------- |
+| image00001.jpg   | apron-001.jpg    | Pregač       | Pregač sa džepom | Pamučni kuhinjski… | kuhinja; pregač |
+| image00002.jpg   | apron-002        | Radni Pregač | Bez rukava       | Polyester, plavi   | rad; uniforma   |
+
+You may use aliases as headers, e.g. `source`, `ouput`, `title`, `caption`, `description`, `keywords`.
+
+### Tips
+
+- Keep headers in the first row; content from subsequent rows only.
+- Avoid extra spaces in filenames; the app trims and lowercases for matching.
+- Only JPEG files are supported.
+
 # React + Vite
 
 This template provides a minimal setup to get React working in Vite with HMR and some ESLint rules.