fix(#11): validate RAW file format before processing

src/main.rs

@@ -179,6 +179,29 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         e
     })?;
 
+    // Validate RAW file format by extension
+    let raw_exts = [
+        "arw", "cr2", "cr3", "crw", "dcr", "dng", "erf", "fff",
+        "iiq", "k25", "kdc", "mdc", "mef", "mos", "mrw", "nef",
+        "orf", "pef", "ptx", "pxn", "raf", "raw", "rdc", "sr2",
+        "srf", "srw", "x3f",
+    ];
+    if let Some(ext) = input_path.extension().and_then(|s| s.to_str()) {
+        let ext_lower = ext.to_lowercase();
+        if !raw_exts.contains(&ext_lower.as_str()) {
+            eprintln!(
+                "Error: '{}' is not a supported RAW format (extension: .{})",
+                input_path.display(),
+                ext_lower
+            );
+            eprintln!("Supported formats: {}", raw_exts.join(", "));
+            return Err("Unsupported file format".into());
+        }
+    } else {
+        eprintln!("Error: Input file has no extension: {}", input_path.display());
+        return Err("File has no extension".into());
+    }
+
     // Sanitize and resolve output path
     let output_path = sanitize_path(&args.output, false).map_err(|e| {
         eprintln!("Error: {}", e);