+static void lowpass_line_c(uint8_t *dstp, ptrdiff_t linesize,
+ const uint8_t *srcp,
+ const uint8_t *srcp_above,
+ const uint8_t *srcp_below)
+{
+ int i;
+ for (i = 0; i < linesize; i++) {
+ // this calculation is an integer representation of
+ // '0.5 * current + 0.25 * above + 0.25 * below'
+ // '1 +' is for rounding.
+ dstp[i] = (1 + srcp[i] + srcp[i] + srcp_above[i] + srcp_below[i]) >> 2;
+ }
+}
+