fixed -g option in src/video2x.c and help message for libplacebo

Signed-off-by: Neo_Chen <chenkolei@gmail.com>

src/video2x.c

@@ -216,7 +216,7 @@ void parse_arguments(int argc, char **argv, struct arguments *arguments) {
     arguments->scaling_factor = 0;
 
     while ((c = getopt_long(
-                argc, argv, "i:o:f:a:c:x:p:b:q:s:w:h:r:m:v", long_options, &option_index
+                argc, argv, "i:o:f:a:c:x:p:b:q:s:w:h:r:m:g:v", long_options, &option_index
             )) != -1) {
         switch (c) {
             case 'i':
@@ -337,7 +337,7 @@ void parse_arguments(int argc, char **argv, struct arguments *arguments) {
             fprintf(
                 stderr,
                 "Error: For libplacebo, shader name/path (-s), width (-w), "
-                "and height (-e) are required.\n"
+                "and height (-h) are required.\n"
             );
             exit(1);
         }