Use safe iteration for reading color palette.

JimBobSquarePants · JimBobSquarePants · commit 6ad24af03c07 · 2023-09-22T17:03:34.000+10:00
diff --git a/src/ImageSharp/Formats/Png/PngDecoderCore.cs b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
@@ -933,10 +933,10 @@ private static void AssignColorPalette(ReadOnlySpan<byte> palette, ReadOnlySpan<
         }
 
         Color[] colorTable = new Color[palette.Length / Unsafe.SizeOf<Rgb24>()];
-        ref Rgb24 paletteBase = ref MemoryMarshal.GetReference(MemoryMarshal.Cast<byte, Rgb24>(palette));
+        ReadOnlySpan<Rgb24> rgbTable = MemoryMarshal.Cast<byte, Rgb24>(palette);
         for (int i = 0; i < colorTable.Length; i++)
         {
-            colorTable[i] = new Color(Unsafe.Add(ref paletteBase, (uint)i));
+            colorTable[i] = new Color(rgbTable[i]);
         }
 
         if (alpha.Length > 0)

Original file line number	Diff line number	Diff line change
`@@ -933,10 +933,10 @@ private static void AssignColorPalette(ReadOnlySpan<byte> palette, ReadOnlySpan<`
`933`	`933`	`}`
`934`	`934`
`935`	`935`	`Color[] colorTable = new Color[palette.Length / Unsafe.SizeOf<Rgb24>()];`
`936`		`- ref Rgb24 paletteBase = ref MemoryMarshal.GetReference(MemoryMarshal.Cast<byte, Rgb24>(palette));`
	`936`	`+ ReadOnlySpan<Rgb24> rgbTable = MemoryMarshal.Cast<byte, Rgb24>(palette);`
`937`	`937`	`for (int i = 0; i < colorTable.Length; i++)`
`938`	`938`	`{`
`939`		`- colorTable[i] = new Color(Unsafe.Add(ref paletteBase, (uint)i));`
	`939`	`+ colorTable[i] = new Color(rgbTable[i]);`
`940`	`940`	`}`
`941`	`941`
`942`	`942`	`if (alpha.Length > 0)`