From c461d55101e6398f3f7f21bcc334eb06fb1a3df7 Mon Sep 17 00:00:00 2001
From: Colin McMillen <colin@semicolin.games>
Date: Tue, 25 Jul 2023 14:28:57 -0400
Subject: [PATCH] start of Exif orientation handling

---
 Program.cs | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/Program.cs b/Program.cs
index 9b83762..36c7220 100644
--- a/Program.cs
+++ b/Program.cs
@@ -27,6 +27,7 @@ public class CameraInfo {
   public static readonly CameraInfo IPHONE_12_MINI = new(new Vector2i(4032, 3024));
 }
 
+// FIXME: switch to immediate mode??
 public class Shader : IDisposable {
   public int Handle;
   private bool init = false;
@@ -165,14 +166,22 @@ public class Photo {
   }
 
   public async void Load() {
-    image = await Image.LoadAsync<Rgba32>(File);
-    TryParseRating(image.Metadata.XmpProfile, out Rating);
-    ExifProfile? exifs = image.Metadata.ExifProfile;
+    // We don't assign to this.image until Load() is done, because we might
+    // edit the image due to rotation (etc) and don't want to try generating
+    // a texture for it until that's already happened.
+    Image<Rgba32> tmpImage = await Image.LoadAsync<Rgba32>(File);
+    TryParseRating(tmpImage.Metadata.XmpProfile, out Rating);
+    ExifProfile? exifs = tmpImage.Metadata.ExifProfile;
     if (exifs != null) {
-      // FIXME: handle Orientation
+      // FIXME: when we write out images, we'll want to correct the Exif Orientation to 1.
       // FIXME: handle date shot / edited (and sort by shot date?)
       // FIXME: PixelXDimension & PixelYDimension hold the image geometry in Exif.
 
+      IExifValue<ushort>? orientation;
+      if (exifs.TryGetValue(ExifTag.Orientation, out orientation)) {
+        Util.RotateImageFromExif(tmpImage, orientation.Value);
+      }
+
       IExifValue<string>? model;
       if (exifs.TryGetValue(ExifTag.Model, out model)) {
         CameraModel = model.Value ?? "";
@@ -238,6 +247,7 @@ public class Photo {
       // foreach (IExifValue exif in exifs.Values) {
       //   Console.WriteLine(exif.Tag.ToString() + " " + exif.GetValue().ToString());
       // }
+      image = tmpImage;
     }
   }
 
@@ -374,6 +384,16 @@ public static class Util {
     return new((int) Math.Ceiling(width), (int) Math.Ceiling(height));
   }
 
+  // https://sirv.com/help/articles/rotate-photos-to-be-upright/
+  public static void RotateImageFromExif(Image<Rgba32> image, ushort orientation) {
+    if (orientation == 1) {
+      return;
+    }
+    if (orientation == 8) {
+      image.Mutate(x => x.RotateFlip(RotateMode.Rotate270, FlipMode.None));
+    }
+  }
+
   public static Texture RenderText(string text) {
     return RenderText(text, 16);
   }
@@ -542,8 +562,8 @@ public class Game : GameWindow {
     // Load textures from JPEGs.
     // 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\2018\06\23");
+    string[] files = Directory.GetFiles(@"G:\DCIM\100EOSR6\");
+    // 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\");