tweaked autocrop

ImageNodes/Images/AutoCropImage.cs

@@ -1,4 +1,5 @@
 using SixLabors.ImageSharp.Formats;
+using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Processing;
 using System.ComponentModel;
 
@@ -27,16 +28,124 @@ public class AutoCropImage : ImageNode
         if (threshold < 0)
             threshold = 0.5f;
 
-        args.Logger?.ILog("Attempting to auto crop using threshold: " + threshold);
-        image.Mutate(c => c.EntropyCrop(threshold));
+        var scaleFactor = originalWidth > 4000 && originalHeight > 4000 ? 10 :
+                          originalWidth > 2000 && originalHeight > 2000 ? 6 :
+                          4;
 
-        if (image.Width == originalWidth && image.Height == originalHeight)
+        // entropycrop of Sixlabors does not give good results if the image has artifacts in it, eg from a scanned in image
+        // so we need to detect the whitespace ourselves.   first we convert to greyscale and downscale, this should remove some artifacts for us
+        // when then look for the outer most non white pixels for out bounds
+        // then we upscale those bounds to the original dimensions and crop with those bounds
+        image.Mutate(c =>
+        {
+            c.Grayscale().Resize(originalWidth / scaleFactor, originalHeight / scaleFactor);
+        });
+        string temp = Path.Combine(args.TempPath, Guid.NewGuid() + ".jpg");
+        image.SaveAsJpeg(temp);
+        var bounds = GetTrimBounds(temp);
+        bounds.X *= scaleFactor;
+        bounds.Y *= scaleFactor;
+        bounds.Width *= scaleFactor;
+        bounds.Height *= scaleFactor;
+        image.Dispose();
+
+        args.Logger?.ILog("Attempting to auto crop using threshold: " + threshold);
+        if (bounds.Width == originalWidth && bounds.Height == originalHeight)
+            return 2;
+
+        using var image2 = Image.Load(args.WorkingFile, out format);
+
+
+        image2.Mutate(c =>
+        {
+            c.Crop(bounds);
+            //c.EntropyCrop(threshold);
+        });
+
+        if (image2.Width == originalWidth && image2.Height == originalHeight)
             return 2;
 
         var formatOpts = GetFormat(args);
-        SaveImage(args, image, formatOpts.file, formatOpts.format ?? format);
-        args.Logger?.ILog($"Image cropped from '{originalWidth}x{originalHeight}' to '{image.Width}x{image.Height}'");
+        SaveImage(args, image2, formatOpts.file, formatOpts.format ?? format);
+        args.Logger?.ILog($"Image cropped from '{originalWidth}x{originalHeight}' to '{image2.Width}x{image2.Height}'");
 
         return 1;
     }
+
+    public Rectangle GetTrimBounds(string file)
+    {
+        int threshhold = 255 - (this.Threshold / 4);
+
+
+        int topOffset = 0;
+        int bottomOffset = 0;
+        int leftOffset = 0;
+        int rightOffset = 0;
+
+
+        using Image<Rgba32> image = Image.Load<Rgba32>(file);
+        bool foundColor = false;
+        // Get left bounds to crop
+        for (int x = 1; x < image.Width && foundColor == false; x++)
+        {
+            for (int y = 1; y < image.Height && foundColor == false; y++)
+            {
+                var color = image[x, y];
+                if (color.R < threshhold || color.G < threshhold || color.B < threshhold)
+                    foundColor = true;
+            }
+            leftOffset += 1;
+        }
+
+
+        foundColor = false;
+        // Get top bounds to crop
+        for (int y = 1; y < image.Height && foundColor == false; y++)
+        {
+            for (int x = 1; x < image.Width && foundColor == false; x++)
+            {
+                var color = image[x, y];
+                if (color.R < threshhold || color.G < threshhold || color.B < threshhold)
+                    foundColor = true;
+            }
+            topOffset += 1;
+        }
+
+
+        foundColor = false;
+        // Get right bounds to crop
+        for (int x = image.Width - 1; x >= 1 && foundColor == false; x--)
+        {
+            for (int y = 1; y < image.Height && foundColor == false; y++)
+            {
+                var color = image[x, y];
+                if (color.R < threshhold || color.G < threshhold || color.B < threshhold)
+                    foundColor = true;
+            }
+            rightOffset += 1;
+        }
+
+
+        foundColor = false;
+        // Get bottom bounds to crop
+        for (int y = image.Height - 1; y >= 1 && foundColor == false; y--)
+        {
+            for (int x = 1; x < image.Width && foundColor == false; x++)
+            {
+                var color = image[x, y];
+                if (color.R < threshhold || color.G < threshhold || color.B < threshhold)
+                    foundColor = true;
+            }
+            bottomOffset += 1;
+        }
+
+
+        var bounds = new Rectangle(
+            leftOffset, 
+            topOffset, 
+            image.Width - leftOffset - rightOffset, 
+            image.Height - topOffset - bottomOffset
+        );
+        return bounds;
+    }
 }

ImageNodes/Tests/ImageTests.cs

@@ -12,7 +12,7 @@ public class ImageNodesTests
     string TestImage1;
     string TestImage2;
     string TempDir;
-    string TestCropImage1, TestCropImage2, TestCropImage3, TestCropImageNoCrop;
+    string TestCropImage1, TestCropImage2, TestCropImage3, TestCropImage4, TestCropImageNoCrop;
 
     public ImageNodesTests()
     {
@@ -25,6 +25,7 @@ public class ImageNodesTests
             TestCropImage1 = @"D:\images\testimages\crop01.jpg";
             TestCropImage2 = @"D:\images\testimages\crop02.jpg";
             TestCropImage3 = @"D:\images\testimages\crop03.jpg";
+            TestCropImage4 = @"D:\images\testimages\crop04.jpg";
             TestCropImageNoCrop = @"D:\images\testimages\nocrop.jpg";
         }
         else
@@ -126,6 +127,8 @@ public class ImageNodesTests
         };
 
         var node = new AutoCropImage();
+        node.Threshold = 50;
+        node.PreExecute(args);
         int result = node.Execute(args);
         
         string log = logger.ToString();
@@ -159,6 +162,32 @@ public class ImageNodesTests
         };
 
         var node = new AutoCropImage();
+        node.Threshold = 50;
+        node.PreExecute(args);                
+        int result = node.Execute(args);
+
+        string log = logger.ToString();
+        Assert.AreEqual(1, result);
+    }
+
+    [TestMethod]
+    public void ImageNodes_Basic_AutoCrop_04()
+    {
+        var logger = new TestLogger();
+        var args = new NodeParameters(TestCropImage4, logger, false, string.Empty)
+        {
+            TempPath = TempDir
+        };
+
+        //var rotate = new ImageRotate();
+        //rotate.Angle = 270;
+        //rotate.PreExecute(args);
+        //rotate.Execute(args);
+
+
+        var node = new AutoCropImage();
+        node.Threshold = 70;
+        node.PreExecute(args);
         int result = node.Execute(args);
 
         string log = logger.ToString();
@@ -175,6 +204,8 @@ public class ImageNodesTests
         };
 
         var node = new AutoCropImage();
+        node.Threshold = 50;
+        node.PreExecute(args);
         int result = node.Execute(args);
 
         string log = logger.ToString();