diff --git a/SerialPrograms/Source/Kernels/ImageFilters/Kernels_ImageFilter_Basic.h b/SerialPrograms/Source/Kernels/ImageFilters/Kernels_ImageFilter_Basic.h
index 48579c547..7d991226a 100644
--- a/SerialPrograms/Source/Kernels/ImageFilters/Kernels_ImageFilter_Basic.h
+++ b/SerialPrograms/Source/Kernels/ImageFilters/Kernels_ImageFilter_Basic.h
@@ -15,12 +15,15 @@
 namespace PokemonAutomation{
 namespace Kernels{
 
-
+// Change certain color in `image_in` and save output to `image_out`.
+//  If `replace_color_within_range` is true, replace the color within range [mins, maxs] with the color `replacement`.
+//  If `replace_color_within_range` is false, replace the color outside of the range with the color `replacement`.
+//  Returns the # of pixels inside the range [mins, maxs].
 size_t filter_rgb32_range(
-    const uint32_t* in, size_t in_bytes_per_row, size_t width, size_t height,
-    uint32_t* out, size_t out_bytes_per_row,
+    const uint32_t* image_in, size_t image_in_bytes_per_row, size_t width, size_t height,
+    uint32_t* image_out, size_t image_out_bytes_per_row,
     uint32_t mins, uint32_t maxs,
-    uint32_t replacement, bool invert
+    uint32_t replacement, bool replace_color_within_range
 );
 
 
diff --git a/SerialPrograms/Source/Kernels/ImageFilters/Kernels_ImageFilter_Basic_Routines.h b/SerialPrograms/Source/Kernels/ImageFilters/Kernels_ImageFilter_Basic_Routines.h
index a64d07ef7..766c7a90a 100644
--- a/SerialPrograms/Source/Kernels/ImageFilters/Kernels_ImageFilter_Basic_Routines.h
+++ b/SerialPrograms/Source/Kernels/ImageFilters/Kernels_ImageFilter_Basic_Routines.h
@@ -16,7 +16,12 @@
 namespace PokemonAutomation{
 namespace Kernels{
 
-
+// Runner interface:
+// - static size_t Runner::VECTOR_SIZE, how many uint32_t in an SIMD vector. Note one pixel is one uint32_t.
+// - Runner::process_full(uint32_t* out, const uint32_t* in), process a full vector: replace pixels in
+//   or out of a specific color range with a particular color.
+// - Runner::process_partial(uint32_t* out, const uint32_t* in, size_t left), process a partial vector:
+//   work only on the first `left` pixels.
 template <typename Runner>
 PA_FORCE_INLINE void filter_per_pixel(
     const uint32_t* image, size_t in_bytes_per_row, size_t width, size_t height,