-// As a convenience, if the flag “pad_from_bottom” is nonzero, the “top” parameter
-// will mean pixels from the bottom (matching OpenGL's usual bottom-left convention),
-// instead of from the top as usual.
+// IntegralPaddingEffect is like PaddingEffect, except that "top" and "left" parameters
+// are int parameters instead of float. This allows it to guarantee one-to-one sampling,
+// which can speed up processing by allowing more effect passes to be collapsed.
+// border_offset_* are still allowed to be float, although you should beware that if
+// you set e.g. border_offset_top to a negative value, you will be sampling outside
+// the edge and will read data that is undefined in one-to-one-mode (could be
+// edge repeat, could be something else). With regular PaddingEffect, such samples
+// are guaranteed to be edge repeat.