frmwriter: handle grayscale formats too

1 files changed, 3 insertions, 2 deletions

diff --git a/src/frmwriter.rs b/src/frmwriter.rs
index 5b50b81..71ad491 100644
--- a/src/frmwriter.rs
+++ b/src/frmwriter.rs
@@ -43,7 +43,8 @@ pub fn write_pgmyuv(pfx: &str, strno: usize, num: u64, frm: NAFrameRef) {
     let stride2 = buf.get_stride(2);
     let u = &dta[base1..][..h2*stride1];
     let v = &dta[base2..][..h2*stride2];
-    if !full_w {
+    let has_chroma = stride1 > 0 && stride2 > 0;
+    if !full_w && has_chroma {
         if !is_flipped {
             for (uline, vline) in u.chunks(stride1).zip(v.chunks(stride2)) {
                 ofile.write_all(&uline[..w2]).unwrap();
@@ -61,7 +62,7 @@ pub fn write_pgmyuv(pfx: &str, strno: usize, num: u64, frm: NAFrameRef) {
                 ofile.write_all(pad.as_slice()).unwrap();
             }
         }
-    } else {
+    } else if has_chroma {
         if !is_flipped {
             for uline in u.chunks(stride1) {
                 ofile.write_all(&uline[..w2]).unwrap();