fix palette import/export issues

Author: LeftofZen

AvaGui/ViewModels/SubObjectTypes/ImageTableViewModel.cs

@@ -216,19 +216,23 @@ public async Task ImportImages()
 				});
 
 				var sortedH = sorted.ToImmutableHashSet();
-				if (G1Provider.G1Elements.Count != sortedH.Count)
-				{
-					throw new ArgumentOutOfRangeException($"Directory doesn't contain the same number of images as expected Directory={sortedH.Count} Expected={G1Provider.G1Elements.Count}");
-				}
 
 				var g1Elements = new List<G1Element32>();
 				var i = 0;
 				foreach (var file in sorted)
 				{
 					var img = Image.Load<Rgba32>(file);
 					Images[i] = img;
-					var currG1 = G1Provider.G1Elements[i++];
-					currG1.ImageData = PaletteMap.ConvertRgba32ImageToG1Data(img, currG1.Flags); // simply overwrite existing pixel data
+					var currG1 = G1Provider.G1Elements[i];
+					currG1 = currG1 with
+					{
+						Width = (int16_t)img.Width,
+						Height = (int16_t)img.Height,
+						Flags = currG1.Flags & ~G1ElementFlags.IsRLECompressed, // SawyerStreamWriter::SaveImageTable does this anyways
+						ImageData = PaletteMap.ConvertRgba32ImageToG1Data(img, currG1.Flags)
+					};
+					G1Provider.G1Elements[i] = currG1;
+					i++;
 				}
 
 				this.RaisePropertyChanged(nameof(Bitmaps));

Dat/PaletteMap.cs

@@ -40,7 +40,7 @@ public PaletteMap(Color[] _palette)
 		public Color[] PaletteColours => Palette.Select(x => x.Color).ToArray();
 
 		public (Color Color, byte Index) Transparent
-			=> Palette[0];
+			=> (Color.FromRgba(0, 0, 0, 0), 0); //Palette[0];
 
 		public (Color Color, byte Index)[] DirectXReserved
 			=> Palette[1..7];

Tests/ImagePaletteConversionTests.cs

@@ -2,6 +2,7 @@
 using OpenLoco.Common.Logging;
 using OpenLoco.Dat.FileParsing;
 using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.PixelFormats;
 
 namespace OpenLoco.Dat.Tests
 {
@@ -13,18 +14,43 @@ public class ImagePaletteConversionTests
 		const string BasePalettePath = "Q:\\Games\\Locomotion\\Palettes\\";
 		readonly ILogger Logger = new Logger();
 
+		[Test]
+		public void TestWrite00000000ToIndex0()
+		{
+			var paletteFile = Path.Combine(BasePalettePath, "palette_32bpp3.png");
+			var paletteMap = Image.Load<Rgba32>(paletteFile);
+			paletteMap[0, 0] = Color.Transparent;
+			paletteMap.SaveAsPng(paletteFile);
+		}
+
+		[Test]
+		public void PaletteIndex0IsTransparent()
+		{
+			var paletteFile = Path.Combine(BasePalettePath, "palette_32bpp3.png");
+			var paletteMap = new PaletteMap(paletteFile);
+
+			Assert.That(paletteMap.Transparent.Color, Is.EqualTo(Color.Transparent));
+		}
+
+		[Test]
+		public void PaletteHasUniqueColours()
+		{
+			var paletteFile = Path.Combine(BasePalettePath, "palette_32bpp3.png");
+			var paletteMap = new PaletteMap(paletteFile);
+
+			Assert.That(paletteMap.Transparent.Color, Is.EqualTo(Color.Transparent));
+			Assert.That(paletteMap.PaletteColours.Length, Is.EqualTo(paletteMap.PaletteColours.ToHashSet().Count));
+		}
+
 		[TestCase("AIRPORT1.DAT")]
 		[TestCase("BALDWIN1.DAT")]
 		[TestCase("FACTORY.DAT")]
 		//[TestCase("INTERDEF.DAT")] // these files use different palettes
 		//[TestCase("WATER1.DAT")]   // these files use different palettes
 		public void G1ElementToPNGAndBack(string objectSource)
 		{
-			var paletteFile = Path.Combine(BasePalettePath, "palette_32bpp.png");
+			var paletteFile = Path.Combine(BasePalettePath, "palette_32bpp3.png");
 			var paletteMap = new PaletteMap(paletteFile);
-
-			Assert.That(paletteMap.Transparent.Color, Is.EqualTo(Color.Transparent));
-
 			var obj = SawyerStreamReader.LoadFullObjectFromFile(Path.Combine(BaseObjDataPath, objectSource), Logger);
 
 			// convert g1 data into an image, and then back