handle ExposureTime edge cases (for long exposures)

use a black texture while loading instead of white

print some more error messages in EXIF edge cases

Program.cs

@@ -166,10 +166,12 @@ public class Photo {
     ExifProfile? exifs = image.Metadata.ExifProfile;
     if (exifs != null) {
       // FIXME: handle Orientation
+
       IExifValue<string>? model;
       if (exifs.TryGetValue(ExifTag.Model, out model)) {
         CameraModel = model.Value;
       }
+
       IExifValue<string>? lensModel;
       if (exifs.TryGetValue(ExifTag.LensModel, out lensModel)) {
         LensModel = lensModel.Value;
@@ -187,7 +189,9 @@ public class Photo {
         if (r.Denominator == 1) {
           FNumber = $"f/{r.Numerator}";
         } else {
-          // FIXME: assert that numerator is 10
+          if (r.Denominator != 10) {
+            Console.WriteLine($"*** WARNING: unexpected FNumber denominator: {r.Denominator}");
+          }
           if (r.Numerator % 10 == 0) {
             FNumber = $"f/{r.Numerator / 10}";
           } else {
@@ -203,8 +207,12 @@ public class Photo {
           ExposureTime = $"1/{r.Denominator}";
         } else if (r.Numerator == 10) {
           ExposureTime = $"1/{r.Denominator / 10}";
+        } else if (r.Denominator == 1) {
+          ExposureTime = $"{r.Numerator }\"";
+        } else if (r.Denominator == 10) {
+          ExposureTime = $"{r.Numerator / 10}.{r.Numerator % 10}\"";
         } else {
-          Console.WriteLine("*** WARNING: unexpected ExposureTime numerator");
+          Console.WriteLine($"*** WARNING: unexpected ExposureTime: {r.Numerator}/{r.Denominator}");
           ExposureTime = r.ToString();
         }
       }
@@ -212,8 +220,13 @@ public class Photo {
       IExifValue<ushort[]>? isoSpeed;
       if (exifs.TryGetValue(ExifTag.ISOSpeedRatings, out isoSpeed)) {
         ushort[]? iso = isoSpeed.Value;
-        if (iso != null && iso.Length >= 1) {
-          IsoSpeed = $"ISO {iso[0]}";
+        if (iso != null) {
+          if (iso.Length != 1) {
+            Console.WriteLine($"*** WARNING: unexpected ISOSpeedRatings array length: {iso.Length}");
+          }
+          if (iso.Length >= 1) {
+            IsoSpeed = $"ISO {iso[0]}";
+          }
         }
       }
       // foreach (IExifValue exif in exifs.Values) {
@@ -364,6 +377,7 @@ public class Game : GameWindow {
   public Game(GameWindowSettings gwSettings, NativeWindowSettings nwSettings) : base(gwSettings, nwSettings) {}
 
   private static Texture TEXTURE_WHITE = new(new Image<Rgba32>(1, 1, new Rgba32(255, 255, 255)));
+  private static Texture TEXTURE_BLACK = new(new Image<Rgba32>(1, 1, new Rgba32(0, 0, 0)));
 
   UiGeometry geometry = new();
 
@@ -507,7 +521,7 @@ public class Game : GameWindow {
     for (int i = 0; i < files.Count(); i++) {
       string file = files[i];
       if (file.ToLower().EndsWith(".jpg")) {
-        Photo photo = new Photo(file, TEXTURE_WHITE);
+        Photo photo = new Photo(file, TEXTURE_BLACK);
         photos.Add(photo);
         await Task.Run( () => { photo.Load(); });
         if (photos.Count == 100) {