icat: a program to print images in the terminal.

Thanks to WizardCoder for implementing the first version of this code. I
had to clean it up quite a bit though.

6 files changed, 134 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..c4a847d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/result
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..775df95
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,25 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1693355128,
+        "narHash": "sha256-+ZoAny3ZxLcfMaUoLVgL9Ywb/57wP+EtsdNGuXUJrwg=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "a63a64b593dcf2fe05f7c5d666eb395950f36bc9",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..81b7d36
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,17 @@
+{
+  outputs = { self, nixpkgs }:
+  let pkgs = nixpkgs.legacyPackages.x86_64-linux; in
+  rec {
+
+    packages.x86_64-linux.icat = pkgs.buildGoModule {
+      pname = "icat";
+      version = "1.0";
+
+      src = self;
+
+      vendorHash = "sha256-WiEK8nq13mdTFnyxDiMRWM1tb60mlZY0fVmtlH5ZWgw=";
+    };
+
+    defaultPackage.x86_64-linux = packages.x86_64-linux.icat;
+  };
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..f2b8f47
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,7 @@
+module icat
+
+go 1.20
+
+require golang.org/x/term v0.11.0
+
+require golang.org/x/sys v0.11.0 // indirect
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..6aed7b2
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,4 @@
+golang.org/x/sys v0.11.0 h1:eG7RXZHdqOJ1i+0lgLgCpSXAp6M3LYlAo6osgSi0xOM=
+golang.org/x/sys v0.11.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/term v0.11.0 h1:F9tnn/DA/Im8nCwm+fX+1/eBwi4qFjRT++MhtVC4ZX0=
+golang.org/x/term v0.11.0/go.mod h1:zC9APTIj3jG3FdV/Ons+XE1riIZXG4aZ4GTHiPZJPIU=
diff --git a/icat.go b/icat.go
new file mode 100644
index 0000000..2b2a847
--- /dev/null
+++ b/icat.go
@@ -0,0 +1,80 @@
+package main
+
+import (
+	"fmt"
+	"golang.org/x/term"
+	"image"
+	_ "image/jpeg"
+	_ "image/png"
+	"os"
+)
+
+func load(filename string) (image.Image, error) {
+	file := os.Stdin
+	if filename != "-" {
+		var err error
+		file, err = os.Open(filename)
+		if err != nil {
+			return nil, err
+		}
+		defer file.Close()
+	}
+
+	img, _, err := image.Decode(file)
+	if err != nil {
+		return nil, fmt.Errorf("decode %q: %s", filename, err)
+	}
+
+	return img, nil
+}
+
+func printImg(filename string) error {
+	img, err := load(filename)
+	if err != nil {
+		return err
+	}
+
+	cols, lines, err := term.GetSize(1)
+	if err != nil {
+		return fmt.Errorf("terminal size: %s", err)
+	}
+	lines-- // Leave a line for the status bar.
+
+	// 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)
+	} else {
+		cols = img.Bounds().Dx() * lines * 5 / 2 / img.Bounds().Dy()
+	}
+
+	// nearest-neighbor interpolation
+	for y := 0; y < lines; y++ {
+		for x := 0; x < cols; x++ {
+			sx := x*img.Bounds().Dx()/cols + img.Bounds().Min.X
+			sy := y*img.Bounds().Dy()/lines + img.Bounds().Min.Y
+			r, g, b, _ := img.At(sx, sy).RGBA()
+			fmt.Printf("\033[48;2;%d;%d;%dm ", r>>8, g>>8, b>>8)
+		}
+		fmt.Println("\033[49m")
+	}
+	return nil
+}
+
+func icat(args []string) error {
+	if len(args) == 0 {
+		args = []string{"-"}
+	}
+	for _, f := range args {
+		if err := printImg(f); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func main() {
+	if err := icat(os.Args[1:]); err != nil {
+		fmt.Fprintf(os.Stderr, "Failed: %s\n", err)
+		os.Exit(1)
+	}
+}