Fix rgb vs bgr especially for grayscale conversion

NAPS2.Images/Storage/ImagePixelFormat.cs

@@ -4,6 +4,6 @@ public enum ImagePixelFormat
 {
     Unsupported,
     BW1,
-    RGB24,
+    RGB24, // This is actually BGR in the binary representation
     ARGB32
 }

NAPS2.Images/Storage/UnsafeImageOps.cs

@@ -5,6 +5,8 @@ namespace NAPS2.Images.Storage;
 // TODO: Make internal?
 // TODO: Improve preconditions to guard against misuse causing access violations
 // TODO: Verify test coverage
+// TODO: If we add a new IMemoryImage implementation, we need to figure out RGB vs BGR (bgr is the Bitmap default)
+// TODO: A lot of the r/g/b naming is off, should be b/g/r (I only corrected it where colors are treated differently)
 public static class UnsafeImageOps
 {
     public static unsafe void ChangeBrightness(IMemoryImage bitmap, float brightnessAdjusted)
@@ -309,9 +311,9 @@ public static class UnsafeImageOps
                         if (x + k < w)
                         {
                             byte* pixel = row + (x + k) * bytesPerPixel;
-                            byte r = *pixel;
+                            byte b = *pixel;
                             byte g = *(pixel + 1);
-                            byte b = *(pixel + 2);
+                            byte r = *(pixel + 2);
                             // Use standard values for grayscale conversion to weight the RGB values
                             int luma = r * 299 + g * 587 + b * 114;
                             if (luma >= thresholdAdjusted)
@@ -422,9 +424,9 @@ public static class UnsafeImageOps
                     for (int x = 0; x < w; x++)
                     {
                         byte* pixel = row + x * bytesPerPixel;
-                        byte r = *pixel;
+                        byte b = *pixel;
                         byte g = *(pixel + 1);
-                        byte b = *(pixel + 2);
+                        byte r = *(pixel + 2);
                         // Use standard values for grayscale conversion to weight the RGB values
                         int luma = r * 299 + g * 587 + b * 114;
                         outRow[x] = luma < thresholdAdjusted;

NAPS2.Sdk.Tests/PdfResources.resx

@@ -131,7 +131,7 @@
     <value>Resources\word_p1_rotated.jpg;System.Drawing.Bitmap, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
   <data name="word_p2_bw" type="System.Resources.ResXFileRef, System.Windows.Forms">
-    <value>Resources\word_p2_bw.jpg;System.Drawing.Bitmap, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+    <value>Resources\word_p2_bw.png;System.Drawing.Bitmap, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
   <data name="image_pdf" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>Resources\image_pdf.pdf;System.Byte[], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>

NAPS2.Sdk/Images/BlankDetector.cs

@@ -43,9 +43,9 @@ public static class BlankDetector
         {
             for (int y = 0; y < image.Height; y++)
             {
-                int r = bytes[stride * y + x * 3];
+                int b = bytes[stride * y + x * 3];
                 int g = bytes[stride * y + x * 3 + 1];
-                int b = bytes[stride * y + x * 3 + 2];
+                int r = bytes[stride * y + x * 3 + 2];
                 // Use standard values for grayscale conversion to weight the RGB values
                 int luma = r * 299 + g * 587 + b * 114;
                 if (luma < whiteThreshold * 1000)

NAPS2.Sdk/Scan/Internal/Twain/TwainMemoryBufferReader.cs

@@ -100,15 +100,14 @@ public static class TwainMemoryBufferReader
                     {
                         int x = memoryBuffer.XOffset + dx;
                         int y = memoryBuffer.YOffset + dy;
-                        // TODO: This might actually be the other way around
-                        // Colors are provided as BGR, they need to be swapped to RGB
-                        // R
+                        // Colors are provided as RGB, they need to be swapped to BGR
+                        // B
                         *(dstPtr + y * dstBytesPerRow + x * 3) =
                             *(srcPtr + dy * srcBytesPerRow + dx * 3 + 2);
                         // G
                         *(dstPtr + y * dstBytesPerRow + x * 3 + 1) =
                             *(srcPtr + dy * srcBytesPerRow + dx * 3 + 1);
-                        // B
+                        // R
                         *(dstPtr + y * dstBytesPerRow + x * 3 + 2) =
                             *(srcPtr + dy * srcBytesPerRow + dx * 3);
                     }