fix typo, improve DivideCeil

src/ImageSharp.Drawing/Processing/Processors/Drawing/DrawImageProcessor.cs

@@ -17,7 +17,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Drawing
     /// Combines two images together by blending the pixels.
     /// </summary>
     /// <typeparam name="TPixelDst">The pixel format of destination image.</typeparam>
-    /// <typeparam name="TPixelSrc">The pixel format os source image.</typeparam>
+    /// <typeparam name="TPixelSrc">The pixel format of source image.</typeparam>
     internal class DrawImageProcessor<TPixelDst, TPixelSrc> : ImageProcessor<TPixelDst>
         where TPixelDst : struct, IPixel<TPixelDst>
         where TPixelSrc : struct, IPixel<TPixelSrc>

src/ImageSharp/Common/ParallelUtils/ParallelHelper.cs

@@ -141,11 +141,6 @@ namespace SixLabors.ImageSharp.ParallelUtils
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static int DivideCeil(int dividend, int divisor)
-        {
-            // TODO: Is there a more efficient way to calculate this?
-            int result = dividend / divisor;
-            return dividend % divisor == 0 ? result : result + 1;
-        }
+        private static int DivideCeil(int dividend, int divisor) => 1 + ((dividend - 1) / divisor);
     }
 }