jpegsave: sync with tiffsave

libvips/foreign/vips2jpeg.c

@@ -667,29 +667,19 @@ set_cinfo(struct jpeg_compress_struct *cinfo,
 	if (progressive)
 		jpeg_simple_progression(cinfo);
 
-	if (in->Bands != 3 ||
-		subsample_mode == VIPS_FOREIGN_SUBSAMPLE_OFF ||
-		(subsample_mode == VIPS_FOREIGN_SUBSAMPLE_AUTO &&
-			qfac >= 90))
-		/* No chroma subsample.
-		 */
-		for (int i = 0; i < in->Bands; i++) {
-			cinfo->comp_info[i].h_samp_factor = 1;
-			cinfo->comp_info[i].v_samp_factor = 1;
-		}
-	else {
-		/* Use 4:2:0 subsampling, we must set this explicitly, since some
-		 * jpeg libraries do not enable chroma subsample by default.
-		 */
+	/* We must set chroma subsampling explicitly since some libjpegs do not
+	 * enable this by default.
+	 */
+	for (int i = 0; i < in->Bands; i++) {
+		cinfo->comp_info[i].h_samp_factor = 1;
+		cinfo->comp_info[i].v_samp_factor = 1;
+	}
+	if (in->Bands == 3 &&
+		(subsample_mode == VIPS_FOREIGN_SUBSAMPLE_ON ||
+			(subsample_mode == VIPS_FOREIGN_SUBSAMPLE_AUTO &&
+				qfac < 90))) {
 		cinfo->comp_info[0].h_samp_factor = 2;
 		cinfo->comp_info[0].v_samp_factor = 2;
-
-		/* Rest should have sampling factors 1,1.
-		 */
-		for (int i = 1; i < in->Bands; i++) {
-			cinfo->comp_info[i].h_samp_factor = 1;
-			cinfo->comp_info[i].v_samp_factor = 1;
-		}
 	}
 
 	/* Only write the JFIF headers if we have no EXIF.