Add width padding for planar ycbcr

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

@@ -3,6 +3,7 @@
 
 using System;
 using System.Buffers;
+using SixLabors.ImageSharp.Formats.Tiff.Utils;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -35,6 +36,13 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
 
             var color = default(TPixel);
             int offset = 0;
+            int widthPadding = 0;
+            if (this.ycbcrSubSampling != null)
+            {
+                // Round to the next integer multiple of horizontalSubSampling.
+                widthPadding = TiffUtils.PaddingToNextInteger(width, this.ycbcrSubSampling[0]);
+            }
+
             for (int y = top; y < top + height; y++)
             {
                 Span<TPixel> pixelRow = pixels.GetRowSpan(y).Slice(left, width);
@@ -45,11 +53,18 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
                     pixelRow[x] = color;
                     offset++;
                 }
+
+                offset += widthPadding;
             }
         }
 
         private static void ReverseChromaSubSampling(int width, int height, int horizontalSubSampling, int verticalSubSampling, Span<byte> planarCb, Span<byte> planarCr)
         {
+            // If width and height are not multiples of ChromaSubsampleHoriz and ChromaSubsampleVert respectively,
+            // then the source data will be padded.
+            width += TiffUtils.PaddingToNextInteger(width, horizontalSubSampling);
+            height += TiffUtils.PaddingToNextInteger(height, verticalSubSampling);
+
             for (int row = height - 1; row >= 0; row--)
             {
                 for (int col = width - 1; col >= 0; col--)

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

@@ -3,6 +3,7 @@
 
 using System;
 using System.Buffers;
+using SixLabors.ImageSharp.Formats.Tiff.Utils;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -46,7 +47,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
             if (this.ycbcrSubSampling != null)
             {
                 // Round to the next integer multiple of horizontalSubSampling.
-                widthPadding = PaddingToNextInteger(width, this.ycbcrSubSampling[0]);
+                widthPadding = TiffUtils.PaddingToNextInteger(width, this.ycbcrSubSampling[0]);
             }
 
             for (int y = top; y < top + height; y++)
@@ -68,8 +69,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
         {
             // If width and height are not multiples of ChromaSubsampleHoriz and ChromaSubsampleVert respectively,
             // then the source data will be padded.
-            width += PaddingToNextInteger(width, horizontalSubSampling);
+            width += TiffUtils.PaddingToNextInteger(width, horizontalSubSampling);
-            height += PaddingToNextInteger(height, verticalSubSampling);
+            height += TiffUtils.PaddingToNextInteger(height, verticalSubSampling);
             int blockWidth = width / horizontalSubSampling;
             int blockHeight = height / verticalSubSampling;
             int cbCrOffsetInBlock = horizontalSubSampling * verticalSubSampling;
@@ -97,16 +98,5 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
                 }
             }
         }
-
-        private static int PaddingToNextInteger(int valueToRoundUp, int subSampling)
-        {
-            if (valueToRoundUp % subSampling == 0)
-            {
-                return 0;
-            }
-
-            int padding = subSampling - (valueToRoundUp % subSampling);
-            return padding;
-        }
     }
 }

src/ImageSharp/Formats/Tiff/Utils/TiffUtils.cs

@@ -98,5 +98,22 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Utils
             color.FromVector4(colorVector);
             return color;
         }
+
+        /// <summary>
+        /// Finds the padding needed to round 'valueToRoundUp' to the next integer multiple of subSampling value.
+        /// </summary>
+        /// <param name="valueToRoundUp">The width or height to round up.</param>
+        /// <param name="subSampling">The sub sampling.</param>
+        /// <returns>The padding.</returns>
+        public static int PaddingToNextInteger(int valueToRoundUp, int subSampling)
+        {
+            if (valueToRoundUp % subSampling == 0)
+            {
+                return 0;
+            }
+
+            int padding = subSampling - (valueToRoundUp % subSampling);
+            return padding;
+        }
     }
 }