From bd826f170329abfbc91fa9bb8074fb9dbb621099 Mon Sep 17 00:00:00 2001
From: James Jackson-South <james_south@hotmail.com>
Date: Sat, 9 May 2020 14:03:16 +0100
Subject: [PATCH] Ensure min dimension of 1px following rounding. Fix #1195

---
 .../Transforms/Resize/ResizeHelper.cs         | 19 ++++++++++++-------
 .../Processors/Transforms/ResizeTests.cs      | 16 ++++++++++++++++
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeHelper.cs b/src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeHelper.cs
index 6066efd1c..6fd87b3f8 100644
--- a/src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeHelper.cs
+++ b/src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeHelper.cs
@@ -72,7 +72,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
 
                 // case ResizeMode.Stretch:
                 default:
-                    return (new Size(width, height), new Rectangle(0, 0, width, height));
+                    return (new Size(Sanitize(width), Sanitize(height)), new Rectangle(0, 0, width, height));
             }
         }
 
@@ -143,7 +143,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
                 }
 
                 // Target image width and height can be different to the rectangle width and height.
-                return (new Size(width, height), new Rectangle(targetX, targetY, targetWidth, targetHeight));
+                return (new Size(Sanitize(width), Sanitize(height)), new Rectangle(targetX, targetY, Sanitize(targetWidth), Sanitize(targetHeight)));
             }
 
             // Switch to pad mode to downscale and calculate from there.
@@ -253,7 +253,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
             }
 
             // Target image width and height can be different to the rectangle width and height.
-            return (new Size(width, height), new Rectangle(targetX, targetY, targetWidth, targetHeight));
+            return (new Size(Sanitize(width), Sanitize(height)), new Rectangle(targetX, targetY, Sanitize(targetWidth), Sanitize(targetHeight)));
         }
 
         private static (Size, Rectangle) CalculateMaxRectangle(
@@ -282,7 +282,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
             }
 
             // Replace the size to match the rectangle.
-            return (new Size(targetWidth, targetHeight), new Rectangle(0, 0, targetWidth, targetHeight));
+            return (new Size(Sanitize(targetWidth), Sanitize(targetHeight)), new Rectangle(0, 0, Sanitize(targetWidth), Sanitize(targetHeight)));
         }
 
         private static (Size, Rectangle) CalculateMinRectangle(
@@ -330,7 +330,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
             }
 
             // Replace the size to match the rectangle.
-            return (new Size(targetWidth, targetHeight), new Rectangle(0, 0, targetWidth, targetHeight));
+            return (new Size(Sanitize(targetWidth), Sanitize(targetHeight)), new Rectangle(0, 0, Sanitize(targetWidth), Sanitize(targetHeight)));
         }
 
         private static (Size, Rectangle) CalculatePadRectangle(
@@ -398,7 +398,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
             }
 
             // Target image width and height can be different to the rectangle width and height.
-            return (new Size(width, height), new Rectangle(targetX, targetY, targetWidth, targetHeight));
+            return (new Size(Sanitize(width), Sanitize(height)), new Rectangle(targetX, targetY, Sanitize(targetWidth), Sanitize(targetHeight)));
         }
 
         private static (Size, Rectangle) CalculateManualRectangle(
@@ -419,9 +419,14 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
             int targetHeight = targetRectangle.Height > 0 ? targetRectangle.Height : height;
 
             // Target image width and height can be different to the rectangle width and height.
-            return (new Size(width, height), new Rectangle(targetX, targetY, targetWidth, targetHeight));
+            return (new Size(Sanitize(width), Sanitize(height)), new Rectangle(targetX, targetY, Sanitize(targetWidth), Sanitize(targetHeight)));
         }
 
         private static void ThrowInvalid(string message) => throw new InvalidOperationException(message);
+
+        private static int Sanitize(int input)
+        {
+            return Math.Max(1, input);
+        }
     }
 }
diff --git a/tests/ImageSharp.Tests/Processing/Processors/Transforms/ResizeTests.cs b/tests/ImageSharp.Tests/Processing/Processors/Transforms/ResizeTests.cs
index aec0d2a1f..5feb8e9f0 100644
--- a/tests/ImageSharp.Tests/Processing/Processors/Transforms/ResizeTests.cs
+++ b/tests/ImageSharp.Tests/Processing/Processors/Transforms/ResizeTests.cs
@@ -605,5 +605,21 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Transforms
                 image.Mutate(x => x.Resize(image.Width / 2, image.Height / 2));
             }
         }
+
+        [Fact]
+        public void Issue1195()
+        {
+            using (var image = new Image<Rgba32>(2, 300))
+            {
+                var size = new Size(50, 50);
+                image.Mutate(x => x
+                    .Resize(
+                        new ResizeOptions
+                        {
+                            Size = size,
+                            Mode = ResizeMode.Max
+                        }));
+            }
+        }
     }
 }