improve coverage

src/ImageSharp/Formats/Tiff/Compression/TiffBaseDecompressor.cs

@@ -36,10 +36,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression
         /// <param name="buffer">The output buffer for uncompressed data.</param>
         public void Decompress(BufferedReadStream stream, ulong stripOffset, ulong stripByteCount, int stripHeight, Span<byte> buffer)
         {
-            if (stripOffset > long.MaxValue || stripByteCount > long.MaxValue)
-            {
-                TiffThrowHelper.ThrowImageFormatException("The StripOffset or StripByteCount value is too big.");
-            }
+            DebugGuard.MustBeLessThanOrEqualTo(stripOffset, (ulong)long.MaxValue, nameof(stripOffset));
+            DebugGuard.MustBeLessThanOrEqualTo(stripByteCount, (ulong)long.MaxValue, nameof(stripByteCount));
 
             stream.Seek((long)stripOffset, SeekOrigin.Begin);
             this.Decompress(stream, (int)stripByteCount, stripHeight, buffer);

src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs

@@ -473,10 +473,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                 TiffThrowHelper.ThrowImageFormatException("The TIFF image frame is missing the ImageWidth");
             }
 
-            if (((ulong)width.Value) > int.MaxValue)
-            {
-                TiffThrowHelper.ThrowImageFormatException("Too big ImageWidth value");
-            }
+            DebugGuard.MustBeLessThanOrEqualTo((ulong)width.Value, (ulong)int.MaxValue, nameof(ExifTag.ImageWidth));
 
             return (int)width.Value;
         }

src/ImageSharp/Metadata/Profiles/Exif/Values/ExifLong8Array.cs

@@ -7,11 +7,6 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Exif
 {
     internal sealed class ExifLong8Array : ExifArrayValue<ulong>
     {
-        public ExifLong8Array(ExifTag<ulong[]> tag)
-            : base(tag)
-        {
-        }
-
         public ExifLong8Array(ExifTagValue tag)
             : base(tag)
         {
@@ -109,7 +104,13 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Exif
 
         private bool SetArray(long[] values)
         {
-            this.Value = Unsafe.As<long[], ulong[]>(ref values);
+            var numbers = new ulong[values.Length];
+            for (int i = 0; i < values.Length; i++)
+            {
+                numbers[i] = (ulong)(values[i] < 0 ? 0 : values[i]);
+            }
+
+            this.Value = numbers;
             return true;
         }
 
@@ -124,7 +125,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Exif
             var numbers = new ulong[values.Length];
             for (int i = 0; i < values.Length; i++)
             {
-                numbers[i] = (ulong)values[i];
+                numbers[i] = (ulong)Numerics.Clamp(values[i], 0, int.MaxValue);
             }
 
             this.Value = numbers;
@@ -148,7 +149,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Exif
             var numbers = new ulong[values.Length];
             for (int i = 0; i < values.Length; i++)
             {
-                numbers[i] = (ulong)values[i];
+                numbers[i] = (ulong)Numerics.Clamp(values[i], 0, short.MaxValue);
             }
 
             this.Value = numbers;

tests/ImageSharp.Tests/Formats/Tiff/BigTiffMetadataTests.cs

@@ -43,9 +43,11 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
 
             Assert.True(long8.TrySetValue(-100L));
             Assert.Equal(-100L, long8.GetValue());
+            Assert.Equal(ExifDataType.SignedLong8, long8.DataType);
 
-            Assert.True(long8.TrySetValue(100L));
-            Assert.Equal(100L, long8.GetValue());
+            Assert.True(long8.TrySetValue(long.MaxValue));
+            Assert.Equal(long.MaxValue, long8.GetValue());
+            Assert.Equal(ExifDataType.SignedLong8, long8.DataType);
         }
 
         [Fact]
@@ -65,14 +67,25 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
             Assert.True(long8.TrySetValue(123));
             Assert.Equal(new[] { 123UL }, long8.GetValue());
 
+            Assert.True(long8.TrySetValue(123u));
+            Assert.Equal(new[] { 123UL }, long8.GetValue());
+
             Assert.True(long8.TrySetValue(123L));
             Assert.Equal(new[] { 123UL }, long8.GetValue());
 
             Assert.True(long8.TrySetValue(123UL));
             Assert.Equal(new[] { 123UL }, long8.GetValue());
 
+            Assert.True(long8.TrySetValue(new short[] { -1, 2, -3, 4 }));
+            Assert.Equal(new ulong[] { 0, 2UL, 0, 4UL }, long8.GetValue());
+
             Assert.True(long8.TrySetValue(new[] { 1, 2, 3, 4 }));
             Assert.Equal(new[] { 1UL, 2UL, 3UL, 4UL }, long8.GetValue());
+            Assert.Equal(ExifDataType.Long, long8.DataType);
+
+            Assert.True(long8.TrySetValue(new[] { 1, 2, 3, 4, long.MaxValue }));
+            Assert.Equal(new[] { 1UL, 2UL, 3UL, 4UL, (ulong)long.MaxValue }, long8.GetValue());
+            Assert.Equal(ExifDataType.Long8, long8.DataType);
         }
 
         [Fact]
@@ -82,9 +95,11 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
 
             Assert.True(long8.TrySetValue(new[] { 0L }));
             Assert.Equal(new[] { 0L }, long8.GetValue());
+            Assert.Equal(ExifDataType.SignedLong8, long8.DataType);
 
-            Assert.True(long8.TrySetValue(new[] { -1L, 2L, -3L, 4L }));
-            Assert.Equal(new[] { -1L, 2L, -3L, 4L }, long8.GetValue());
+            Assert.True(long8.TrySetValue(new[] { -1L, 2L, long.MinValue, 4L }));
+            Assert.Equal(new[] { -1L, 2L, long.MinValue, 4L }, long8.GetValue());
+            Assert.Equal(ExifDataType.SignedLong8, long8.DataType);
         }
     }
 }