Improve usage

2 files changed, 30 insertions, 19 deletions

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..0dc67b9
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+# The worst terminal image viewer
+
+seriously just use img2sixel
diff --git a/icat.go b/icat.go
index 01f0400..4bcfb45 100644
--- a/icat.go
+++ b/icat.go
@@ -2,6 +2,8 @@ package main
 
 import (
 	"bufio"
+	"errors"
+	"flag"
 	"fmt"
 	"image"
 	_ "image/jpeg"
@@ -12,8 +14,6 @@ import (
 	"golang.org/x/term"
 )
 
-var stdout = bufio.NewWriter(os.Stdout)
-
 func load(filename string) (image.Image, error) {
 	file := os.Stdin
 	if filename != "-" {
@@ -33,12 +33,7 @@ func load(filename string) (image.Image, error) {
 	return img, nil
 }
 
-func printImg(filename string, cols, lines int) error {
-	img, err := load(filename)
-	if err != nil {
-		return err
-	}
-
+func printImg(img image.Image, cols, lines int) error {
 	// Try not to stretch the image.
 	if img.Bounds().Dy()*cols <= img.Bounds().Dx()*lines*5/2 {
 		lines = img.Bounds().Dy() * cols / (img.Bounds().Dx() * 5 / 2)
@@ -49,42 +44,55 @@ func printImg(filename string, cols, lines int) error {
 	dst := image.NewRGBA(image.Rect(0, 0, cols, 2*lines))
 	draw.BiLinear.Scale(dst, dst.Bounds(), img, img.Bounds(), draw.Over, nil)
 
+	w := bufio.NewWriter(os.Stdout)
+	defer w.Flush()
 	for y := 0; y < 2*lines; y += 2 {
 		for x := 0; x < cols; x++ {
 			hiR, hiG, hiB, _ := dst.At(x, y).RGBA()
 			loR, loG, loB, _ := dst.At(x, y+1).RGBA()
-			fmt.Fprintf(stdout, "\033[38;2;%d;%d;%dm\033[48;2;%d;%d;%dm▀",
+			fmt.Fprintf(w, "\033[38;2;%d;%d;%dm\033[48;2;%d;%d;%dm▀",
 				hiR>>8, hiG>>8, hiB>>8,
 				loR>>8, loG>>8, loB>>8)
 		}
-		fmt.Fprintln(stdout, "\033[49m")
+		fmt.Fprintln(w, "\033[49m")
 	}
-	fmt.Fprint(stdout, "\033[39m")
+	fmt.Fprint(w, "\033[39m")
 	return nil
 }
 
 func icat(args []string) error {
+	if len(args) == 0 {
+		return errors.New("missing positional argument")
+	}
+	if len(args) > 1 {
+		return errors.New("too many positional arguments")
+	}
+	file := args[0]
+
 	cols, lines, err := term.GetSize(1)
 	if err != nil {
 		return fmt.Errorf("terminal size: %s", err)
 	}
 	lines-- // Leave a line for the status bar.
 
-	if len(args) == 0 {
-		args = []string{"-"}
+	img, err := load(file)
+	if err != nil {
+		return err
 	}
 
-	defer stdout.Flush()
-	for _, f := range args {
-		if err := printImg(f, cols, lines); err != nil {
-			return err
-		}
+	if err := printImg(img, cols, lines); err != nil {
+		return err
 	}
 	return nil
 }
 
 func main() {
-	if err := icat(os.Args[1:]); err != nil {
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: icat FILE\n")
+	}
+	flag.Parse()
+
+	if err := icat(flag.Args()); err != nil {
 		fmt.Fprintf(os.Stderr, "Failed: %s\n", err)
 		os.Exit(1)
 	}