feat(rcrop): Negative counts for #rows or #columns cut from the ends

doc/man/man1/rcrop.1

@@ -1,4 +1,4 @@
-.\" RCSid "$Id: rcrop.1,v 1.8 2023/12/12 16:31:45 greg Exp $"
+.\" RCSid "$Id: rcrop.1,v 1.9 2024/05/17 20:50:57 greg Exp $"
 .TH RCROP 1 3/14/2022 RADIANCE
 .SH NAME
 rcrop - crop RADIANCE matrix or picture
@@ -35,6 +35,8 @@ If a 0 value is specified for the number of rows to copy, then all rows
 will be copied, starting from row0.
 Similarly, a 0 value for the number of columns to copy implies all
 columns >= col0 will be copied.
+A negative count for the number of rows or columns cuts the
+corresponding amount off the end(s).
 .PP
 Using
 .I rcrop

doc/notes/ReleaseNotes

@@ -2693,3 +2693,5 @@ scenes with sharp cut-offs.
 
 Added -i option to gendaymtx to match -i option of gendaylit.
 Thanks to Yongqing for initial implementation.
+
+Changed rcrop so negative #rows or #cols counts back from end.

src/util/rcrop.c

@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: rcrop.c,v 1.15 2024/05/16 18:59:19 greg Exp $";
+static const char RCSid[] = "$Id: rcrop.c,v 1.16 2024/05/17 20:50:57 greg Exp $";
 #endif
 /*
  * rcrop.c - crop a Radiance picture or matrix data
@@ -269,7 +269,7 @@ main(int argc, char *argv[])
 	cmin = atoi(argv[2]);
 	nrows = atoi(argv[3]);
 	ncols = atoi(argv[4]);
-	if ((rmin < 0) | (cmin < 0) | (nrows < 0) | (ncols < 0))
+	if ((rmin < 0) | (cmin < 0))
 		goto usage;
 	if (argc <= 5)
 		SET_FILE_BINARY(fp);
@@ -301,10 +301,10 @@ main(int argc, char *argv[])
 		fputs(": missing input dimensions\n", stderr);
 		return(1);
 	}
-	if (!nrows)
-		nrows = numscans(&res) - rmin;
-	if (!ncols)
-		ncols = scanlen(&res) - cmin;
+	if (nrows <= 0 )
+		nrows += numscans(&res) - rmin;
+	if (ncols <= 0)
+		ncols += scanlen(&res) - cmin;
 	if ((nrows <= 0) | (ncols <= 0) |
 			(rmin+nrows > numscans(&res)) |
 			(cmin+ncols > scanlen(&res))) {