Fix issue with white is zero with 24 and 32 bit

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/WhiteIsZero24TiffColor{TPixel}.cs

@@ -31,6 +31,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
             color.FromVector4(TiffUtils.Vector4Default);
             byte[] buffer = new byte[4];
             int bufferStartIdx = this.isBigEndian ? 1 : 0;
+            const uint maxValue = 0xFFFFFF;
 
             Span<byte> bufferSpan = buffer.AsSpan(bufferStartIdx);
             int offset = 0;
@@ -42,7 +43,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
                     for (int x = 0; x < pixelRow.Length; x++)
                     {
                         data.Slice(offset, 3).CopyTo(bufferSpan);
-                        ulong intensity = TiffUtils.ConvertToUIntBigEndian(buffer);
+                        ulong intensity = maxValue - TiffUtils.ConvertToUIntBigEndian(buffer);
                         offset += 3;
 
                         pixelRow[x] = TiffUtils.ColorScaleTo24Bit(intensity, color);
@@ -53,7 +54,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
                     for (int x = 0; x < pixelRow.Length; x++)
                     {
                         data.Slice(offset, 3).CopyTo(bufferSpan);
-                        ulong intensity = TiffUtils.ConvertToUIntLittleEndian(buffer);
+                        ulong intensity = maxValue - TiffUtils.ConvertToUIntLittleEndian(buffer);
                         offset += 3;
 
                         pixelRow[x] = TiffUtils.ColorScaleTo24Bit(intensity, color);

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/WhiteIsZero32TiffColor{TPixel}.cs

@@ -29,6 +29,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
             // we define our own defaults as a workaround. See: https://github.com/dotnet/runtime/issues/55623
             var color = default(TPixel);
             color.FromVector4(TiffUtils.Vector4Default);
+            const uint maxValue = 0xFFFFFFFF;
 
             int offset = 0;
             for (int y = top; y < top + height; y++)
@@ -38,7 +39,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
                 {
                     for (int x = 0; x < pixelRow.Length; x++)
                     {
-                        ulong intensity = TiffUtils.ConvertToUIntBigEndian(data.Slice(offset, 4));
+                        ulong intensity = maxValue - TiffUtils.ConvertToUIntBigEndian(data.Slice(offset, 4));
                         offset += 4;
 
                         pixelRow[x] = TiffUtils.ColorScaleTo32Bit(intensity, color);
@@ -48,7 +49,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
                 {
                     for (int x = 0; x < pixelRow.Length; x++)
                     {
-                        ulong intensity = TiffUtils.ConvertToUIntLittleEndian(data.Slice(offset, 4));
+                        ulong intensity = maxValue - TiffUtils.ConvertToUIntLittleEndian(data.Slice(offset, 4));
                         offset += 4;
 
                         pixelRow[x] = TiffUtils.ColorScaleTo32Bit(intensity, color);

tests/ImageSharp.Tests/TestImages.cs

@@ -600,16 +600,16 @@ namespace SixLabors.ImageSharp.Tests
             public const string Flower16BitGray = "Tiff/flower-minisblack-16.tiff";
             public const string Flower16BitGrayLittleEndian = "Tiff/flower-minisblack-16_lsb.tiff";
             public const string Flower16BitGrayMinIsWhiteLittleEndian = "Tiff/flower-miniswhite-16_lsb.tiff";
-            public const string Flower16BitGrayMinIsWhiteBigEndian = "Tiff/flower-miniswhite-16.tiff";
-            public const string Flower24BitGray = "Tiff/flower-minisblack-24.tiff";
+            public const string Flower16BitGrayMinIsWhiteBigEndian = "Tiff/flower-miniswhite-16_msb.tiff";
+            public const string Flower24BitGray = "Tiff/flower-minisblack-24_msb.tiff";
             public const string Flower24BitGrayLittleEndian = "Tiff/flower-minisblack-24_lsb.tiff";
-            public const string Flower32BitGray = "Tiff/flower-minisblack-32.tiff";
+            public const string Flower32BitGray = "Tiff/flower-minisblack-32_msb.tiff";
             public const string Flower32BitGrayLittleEndian = "Tiff/flower-minisblack-32_lsb.tiff";
             public const string Flower32BitFloatGray = "Tiff/flower-minisblack-float32_msb.tiff";
             public const string Flower32BitFloatGrayLittleEndian = "Tiff/flower-minisblack-float32_lsb.tiff";
             public const string Flower32BitFloatGrayMinIsWhite = "Tiff/flower-miniswhite-float32_msb.tiff";
             public const string Flower32BitFloatGrayMinIsWhiteLittleEndian = "Tiff/flower-miniswhite-float32_lsb.tiff";
-            public const string Flower32BitGrayMinIsWhite = "Tiff/flower-miniswhite-32.tiff";
+            public const string Flower32BitGrayMinIsWhite = "Tiff/flower-miniswhite-32_msb.tiff";
             public const string Flower32BitGrayMinIsWhiteLittleEndian = "Tiff/flower-miniswhite-32_lsb.tiff";
 
             public const string Issues1716Rgb161616BitLittleEndian = "Tiff/Issues/Issue1716.tiff";

tests/Images/Input/Tiff/flower-miniswhite-32.tiff

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:514417ead3d6c5c6ca33374ef0bb6ecbe5f875a266519d4cbaa4a6b91033d243
-size 12778

tests/Images/Input/Tiff/flower-miniswhite-32_lsb.tiff

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:64c948aa03bc4a24cd1d68bb18b5031c119936154a90f1cb1d9aaabd854c5d9b
+oid sha256:17139bc00d9fe2905fbac9226120d2823ea17a10a39b140970122153ec23265d
 size 12778

tests/Images/Input/Tiff/flower-miniswhite-32_msb.tiff

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:17139bc00d9fe2905fbac9226120d2823ea17a10a39b140970122153ec23265d
+size 12778