Fix stride calculation for all packed pixel formats

.gitignore

@@ -196,6 +196,9 @@ PublishScripts/
 *.nuget.props
 *.nuget.targets
 
+# NuGet executable
+.nuget/nuget.exe
+
 # Microsoft Azure Build Output
 csx/
 *.build.csdef

src/VpxVideoEncoder.cs

@@ -94,7 +94,7 @@ public byte[] EncodeVideo(int width, int height, byte[] sample, VideoPixelFormat
                 }
                 else
                 {
-                    int stride = pixelFormat == VideoPixelFormatsEnum.Bgra ? width * 4 : width * 3;
+                    int stride = GetStride(width, pixelFormat);
                     var i420Buffer = PixelConverter.ToI420(width, height, stride, sample, pixelFormat);
                     encodedBuffer = _vp8Encoder.Encode(i420Buffer, vpxmd.VpxImgFmt.VPX_IMG_FMT_I420, _forceKeyFrame);
                 }
@@ -135,6 +135,24 @@ public IEnumerable<VideoSample> DecodeVideo(byte[] frame, VideoPixelFormatsEnum
             }
         }
 
+        private static int RoundUp(int value, int to) => (value + to - 1) / to * to;
+
+        private static int BytesPerPixel(VideoPixelFormatsEnum pixelFormat) => pixelFormat switch
+        {
+            VideoPixelFormatsEnum.Bgra => 4,
+            VideoPixelFormatsEnum.Rgba => 4,
+            VideoPixelFormatsEnum.Rgb  => 3,
+            VideoPixelFormatsEnum.Bgr  => 3,
+            _ => throw new ArgumentException($"Unsupported pixel format for bytes-per-pixel calculation: {pixelFormat}", nameof(pixelFormat))
+        };
+
+        /// <summary>
+        /// Calculates the row stride in bytes for the given width and pixel format,
+        /// rounding up to the nearest 4-byte boundary as required by most bitmap formats.
+        /// </summary>
+        private static int GetStride(int width, VideoPixelFormatsEnum pixelFormat) =>
+            RoundUp(value: width * BytesPerPixel(pixelFormat), to: 4);
+
         public void Dispose()
         {
             _vp8Encoder?.Dispose();