treat all pixels with Alpha=0 the same way

Author: LeftofZen

Dat/FileParsing/SawyerStreamWriter.cs

@@ -283,26 +283,29 @@ static uint8_t RotateLeft(uint8_t value, uint8_t shift)
 			return (uint8_t)((value << shift) | (value >> (8 - shift)));
 		}
 
-		// this is ugly as all hell but it works. plenty of room for cleanup and optimisation
 		public static byte[] EncodeRLEImageData(G1Element32 img)
+			=> EncodeRLEImageData(img.Flags, img.ImageData, img.Width, img.Height);
+
+		// this is ugly as all hell but it works. plenty of room for cleanup and optimisation
+		public static byte[] EncodeRLEImageData(G1ElementFlags flags, byte[] imageData, int width, int height)
 		{
 			using var ms = new MemoryStream();
 
 			var lines = new List<List<(int StartX, List<byte> RunBytes)>>();
 
 			// calculate the segments per line in the input image
-			foreach (var line in img.ImageData.Chunk(img.Width))
+			foreach (var line in imageData.Chunk(width))
 			{
 				List<(int StartX, List<byte> RunBytes)> segments = [];
-				for (var x = 0; x < img.Width;)
+				for (var x = 0; x < width;)
 				{
 					// find the start of a segment. previous pixel may be a segment
 					if (line[x] != 0x0)
 					{
 						// find the end
 						var startOfSegment = x;
 						List<byte> run = [];
-						while (x < img.Width && line[x] != 0x0 && run.Count < 127) // runs can only be 127 bytes in length. if the run is truly longer, then it gets split into multiple runs
+						while (x < width && line[x] != 0x0 && run.Count < 127) // runs can only be 127 bytes in length. if the run is truly longer, then it gets split into multiple runs
 						{
 							run.Add(line[x]);
 							x++;
@@ -322,7 +325,7 @@ public static byte[] EncodeRLEImageData(G1Element32 img)
 			// write source pointers. will be (2 * img.Height) bytes. need to know RLE data first to know the offsets
 			var headerOffset = lines.Count * 2;
 			var bytesTotal = 0;
-			for (var yy = 0; yy < img.Height; ++yy)
+			for (var yy = 0; yy < height; ++yy)
 			{
 				// bytes per previous line is the sum of all the bytes in the runs plus the number of line segments * 2
 				var bytesPreviousLine = yy == 0

Dat/PaletteMap.cs

@@ -40,7 +40,9 @@ public PaletteMap(Color[] _palette)
 		public (Color Color, byte Index)[] Palette { get; set; }
 
 		public static (Color Color, byte Index) Transparent
-			=> (Color.FromRgba(0, 0, 0, 0), 0); //Palette[0];
+			=> (TransparentPixel, 0); //Palette[0];
+
+		public static readonly Color TransparentPixel = Color.FromRgba(0, 0, 0, 0);
 
 		public (Color Color, byte Index)[] TextRendering
 			=> Palette[1..7];
@@ -179,6 +181,11 @@ public bool TryConvertG1ToRgba32Bitmap(G1Element32 g1Element, out Image<Rgba32>?
 
 		byte ColorToPaletteIndex(Color c)
 		{
+			if (c.ToPixel<Rgba32>().A == 0)
+			{
+				c = TransparentPixel;
+			}
+
 			var reserved = ReservedColours.Where(cc => cc.Color == c);
 			if (reserved.Any())
 			{

Dat/Types/G1Element32.cs

@@ -57,9 +57,12 @@ public ReadOnlySpan<byte> Write()
 		}
 
 		public byte[] GetImageDataForSave()
-			=> Flags.HasFlag(G1ElementFlags.IsRLECompressed)
-				? SawyerStreamWriter.EncodeRLEImageData(this)
-				: ImageData;
+			=> GetImageDataForSave(Flags, ImageData, Width, Height);
+
+		public static byte[] GetImageDataForSave(G1ElementFlags flags, byte[] imageData, int width, int height)
+			=> flags.HasFlag(G1ElementFlags.IsRLECompressed)
+				? SawyerStreamWriter.EncodeRLEImageData(flags, imageData, width, height)
+				: imageData;
 
 		public bool Validate() => true;
 	}

Gui/ViewModels/SubObjectTypes/ImageTableViewModel.cs

@@ -379,7 +379,7 @@ void UpdateImage(Image<Rgba32> img, int index)
 			{
 				Width = (int16_t)img.Width,
 				Height = (int16_t)img.Height,
-				Flags = currG1.Flags & ~G1ElementFlags.IsRLECompressed, // SawyerStreamWriter::SaveImageTable does this anyways
+				Flags = currG1.Flags,
 				ImageData = PaletteMap.ConvertRgba32ImageToG1Data(img, currG1.Flags),
 				XOffset = currG1.XOffset,
 				YOffset = currG1.YOffset