doc: help message and README added

1 files changed, 29 insertions, 1 deletions

diff --git a/src/main.c b/src/main.c
index 370ece8..add73f7 100644
--- a/src/main.c
+++ b/src/main.c
@@ -15,10 +15,36 @@ static void usage(void);
 void
 usage(void)
 {
-    fprintf(stderr, "Usage: dsco [INPUT] -f [edge|blur] [-o OUTPUT]\n");
+    fprintf(stderr, "Usage: dsco [INPUT] -f [edge|blur|sharpen] [-o OUTPUT]\n");
     exit(1);
 }
 
+void
+help(void)
+{
+    fprintf(stdout,
+            "Usage:\n"
+            "   dsco [INPUT] -f [edge|blur|sharpen] [-o OUTPUT]\n"
+            "\n"
+            "Options:\n"
+            "    -o     output file [default: /dev/stdout] \n"
+            "    -f     filter to use\n"
+            "\n"
+            "           edge:       -1 -1 -1\n"
+            "                       -1  8 -1\n"
+            "                       -1 -1 -1\n"
+            "\n"
+            "           sharpen:     0 -1  0\n"
+            "                       -1  5 -1\n"
+            "                        0 -1  0\n"
+            "\n"
+            "           blur:        1  2  1\n"
+            "                  1/16  2  4  2\n"
+            "                        1  2  1\n"
+            );
+    exit(0);
+}
+
 Image
 image_convolution(Image input, float kernel[9])
 {
@@ -138,6 +164,8 @@ int main(int argc, char *argv[])
         case 0:
             in_file = cli_arg;
             break;
+        case 'h':
+            help();
         default:
             usage();
         }