a smal bug

Former-commit-id: c6e0afbd230747057de8314c9599821c69dc1ffe
Former-commit-id: be47dfa7a12de85db15a8c00ac434952213fafbb
Former-commit-id: 891a14bf95046a3a8eb5108c6e389060a01a5094

src/ImageProcessorCore/Samplers/Processors/SkewProcessor.cs

@@ -98,41 +98,42 @@ namespace ImageProcessorCore
         {
             int skewMaxX = target.Width - source.Width;
             int skewMaxY = target.Height - source.Height;
-            int offesetX = 0;
-            int offesetY = 0;
-
-            if (ImageMaths.DegreesToRadians(angleX) < 0)
-            {
-                offesetX = skewMaxX;
-                skewMaxX = -skewMaxX;
-
-            }
-            if (ImageMaths.DegreesToRadians(angleY) < 0)
-            {
-                offesetY = skewMaxY;
-              //  skewMaxY = -skewMaxY;
-
-            }
-
-
-
 
+            bool revX = ImageMaths.DegreesToRadians(angleX) < 0;
+            bool revY = ImageMaths.DegreesToRadians(angleY) < 0;
             Parallel.For(
               0,
               source.Height,
               sy =>
               {
+                  int deltaX;
+                  if (revX)
+                  {
+                      deltaX = ((skewMaxX * (-sy + (source.Height - 1))) / (source.Height - 1));
+                  }
+                  else
+                  {
+                      deltaX = (((skewMaxX * sy)) / (source.Height - 1));
+                  }
 
                   for (int sx = 0; sx < source.Width; sx++)
                   {
-                     int skewY = ((skewMaxX * (sy)) / (source.Height - 1)) + offesetX;
-                     int skewX = ((skewMaxY * (sx-source.Width-1)) / (source.Width - 1))+ offesetY;
-                     target[skewY + sx,  sy +skewX ] = source[sx, sy];
+                      int deltaY;
+                      if (revY)
+                      {
+                          deltaY = ((((skewMaxY * -sx ))+ (skewMaxY-1)) -(skewMaxY-1)) / (source.Width - 1) + skewMaxY;
+                          //deltaY = (((skewMaxY * sx)) / (source.Height - 1));
+                         // deltaY = -deltaY + skewMaxY;
+                          //deltaY = 0;
+                      }
+                      else
+                      {
+                          deltaY = ((skewMaxY * sx) / (source.Width - 1));
+                      }
+                      target[deltaX + sx, sy + deltaY] = source[sx, sy];
                   }
                   this.OnRowProcessed();
               });
-
-
         }
 
 

tests/ImageProcessorCore.Tests/Processors/Samplers/SamplerTests.cs

@@ -500,7 +500,7 @@
                     using (Image image = new Image(stream))
                     using (FileStream output = File.OpenWrite($"TestOutput/Skew/{filename}"))
                     {
-                        image.Skew(5, -2, this.ProgressUpdate)
+                        image.Skew(10, -20, this.ProgressUpdate)
                              .Save(output);
                     }