Added QoL throw helper method for jpeg w/h size check before encoding

src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs

@@ -118,14 +118,14 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         {
             Guard.NotNull(image, nameof(image));
             Guard.NotNull(stream, nameof(stream));
-            cancellationToken.ThrowIfCancellationRequested();
 
-            const ushort max = JpegConstants.MaxLength;
+            if (image.Width >= JpegConstants.MaxLength || image.Height >= JpegConstants.MaxLength)
-            if (image.Width >= max || image.Height >= max)
             {
-                throw new ImageFormatException($"Image is too large to encode at {image.Width}x{image.Height}.");
+                JpegThrowHelper.ThrowDimensionsTooLarge(image.Width, image.Height);
             }
 
+            cancellationToken.ThrowIfCancellationRequested();
+
             this.outputStream = stream;
             ImageMetadata metadata = image.Metadata;
 

src/ImageSharp/Formats/Jpeg/JpegThrowHelper.cs

@@ -46,5 +46,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
 
         [MethodImpl(InliningOptions.ColdPath)]
         public static void ThrowInvalidImageDimensions(int width, int height) => throw new InvalidImageContentException($"Invalid image dimensions: {width}x{height}.");
+
+        [MethodImpl(InliningOptions.ColdPath)]
+        public static void ThrowDimensionsTooLarge(int width, int height) => throw new ImageFormatException($"Image is too large to encode at {width}x{height} for JPEG format.");
     }
 }