morph: prefer bitwise NOT over bitwise XOR

`~p` and `p ^ 255` produce the same result on uchar images, as XOR affects only the lowest 8 bits.
kleisauke · Nov 3, 2024 · 4e0b1b2 · 4e0b1b2
1 parent 302689a
commit 4e0b1b2
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Showing 2 changed files with 4 additions and 6 deletions.
diff --git a/libvips/morphology/morph.c b/libvips/morphology/morph.c
@@ -712,7 +712,7 @@ vips_dilate_gen(VipsRegion *out_region,
 			 */
 			result = 0;
 			for (i = 0; i < seq->nn128; i++)
-				result |= !coeff[i] ? p[off[i]] ^ 255 : p[off[i]];
+				result |= !coeff[i] ? ~p[off[i]] : p[off[i]];
 
 			*q = result;
 		}

diff --git a/libvips/morphology/morph_hwy.cpp b/libvips/morphology/morph_hwy.cpp
@@ -89,7 +89,7 @@ vips_dilate_uchar_hwy(VipsRegion *out_region, VipsRegion *ir, VipsRect *r,
 				 */
 				auto pix = LoadU(du8, p + offsets[i]);
 
-				pix = IfThenElse(Ne(mmk, one), Xor(pix, one), pix);
+				pix = IfThenElse(Ne(mmk, one), AndNot(pix, one), pix);
 				sum = Or(sum, pix);
 			}
 
@@ -109,7 +109,7 @@ vips_dilate_uchar_hwy(VipsRegion *out_region, VipsRegion *ir, VipsRect *r,
 				auto pix = LoadU(du8, p + offsets[i]);
 
 				if (!coeff[i])
-					pix = Xor(pix, one);
+					pix = AndNot(pix, one);
 				sum = Or(sum, pix);
 			}
 
@@ -146,9 +146,7 @@ vips_erode_uchar_hwy(VipsRegion *out_region, VipsRegion *ir, VipsRect *r,
 				 */
 				auto pix = LoadU(du8, p + offsets[i]);
 
-				pix = IfThenElse(Ne(mmk, one),
-					AndNot(pix, one),
-					pix);
+				pix = IfThenElse(Ne(mmk, one), AndNot(pix, one), pix);
 				sum = And(sum, pix);
 			}