add some things to exif output

Program.cs

@@ -231,10 +231,24 @@ public class Photo {
     Directory.CreateDirectory(directory);
     string filename = System.IO.Path.Combine(directory, System.IO.Path.GetFileName(Filename));
     Console.WriteLine("saving " + filename);
-    // FIXME: update JPEG metadata.
+    // FIXME: update Rating data.
+    // FIXME: add comments / captions as ImageDescription?
+    // FIXME: strip some Exif tags for privacy reasons?
     // FIXME: warn if the file already exists?
     using (Image<Rgba32> image = await Image.LoadAsync<Rgba32>(Filename)) {
-      // Util.RotateImageFromExif(image, Orientation);
+      Util.RotateImageFromExif(image, Orientation);
+
+      ExifProfile exif = image.Metadata.ExifProfile ?? new();
+      exif.SetValue<ushort>(ExifTag.Orientation, 1);
+      exif.SetValue<string>(ExifTag.Artist, "Colin McMillen");
+      exif.SetValue<string>(ExifTag.Copyright, "Colin McMillen");
+      exif.SetValue<string>(ExifTag.Software, "Totte");
+      DateTime now = DateTime.Now;
+      string datetime = String.Format(
+        "{0:D4}:{1:D2}:{2:D2} {3:D2}:{4:D2}:{5:D2}",
+        now.Year, now.Month, now.Day, now.Hour, now.Minute, now.Second);
+      exif.SetValue<string>(ExifTag.DateTime, datetime);
+
       await image.SaveAsync(filename, encoder);
     }
   }
@@ -285,6 +299,8 @@ public class Photo {
   // Modification Date/Time – Modification date of the digital image file
   // Exif DateTime (306, 0x132) and SubSecTime (37520, 0x9290)
   // XMP (xmp:ModifyDate)
+  //
+  // See also: https://exiftool.org/TagNames/EXIF.html
   private void ParseExif(ExifProfile? exifs) {
     if (exifs == null) {
       return;
@@ -322,6 +338,7 @@ public class Photo {
       }
     }
 
+    // FIXME: could also show ExposureBiasValue, ExposureMode, ExposureProgram?
     IExifValue<Rational>? exposureTime;
     if (exifs.TryGetValue(ExifTag.ExposureTime, out exposureTime)) {
       Rational r = exposureTime.Value;
@@ -804,8 +821,9 @@ public class Game : GameWindow {
 
     // Load photos from a directory.
     // string[] files = Directory.GetFiles(@"c:\users\colin\desktop\photos-test\");
-    string[] files = Directory.GetFiles(@"c:\users\colin\pictures\photos\2023\07\14\");
-    // string[] files = Directory.GetFiles(@"G:\DCIM\100EOSR6\");
+    // string[] files = Directory.GetFiles(@"c:\users\colin\pictures\photos\2023\07\14\");
+    string[] files = Directory.GetFiles(@"G:\DCIM\100EOSR6\");
+    // string[] files = Directory.GetFiles(@"c:\users\colin\desktop\totte-output\2023\07\28");
     // string[] files = Directory.GetFiles(@"C:\Users\colin\Pictures\photos\2018\06\23");
     // string[] files = Directory.GetFiles(@"C:\Users\colin\Desktop\Germany all\104D7000");
     // string[] files = Directory.GetFiles(@"C:\Users\colin\Desktop\many-birds\");
@@ -894,7 +912,6 @@ public class Game : GameWindow {
     JpegEncoder encoder = new JpegEncoder() { Quality = 100 };
     string outputRoot = @"c:\users\colin\desktop\totte-output";
     foreach (Photo p in photos) {
-      // p.SaveAsJpeg(outputRoot, encoder);
       await Task.Run( () => { p.SaveAsJpeg(outputRoot, encoder); });
     }
   }