Added image-diff executable

CHANGELOG.md

@@ -1,4 +1,6 @@
 # image-diff changelog
+1.5.0 - Added `image-diff` executable
+
 1.4.0 - Moved from `crop` to `extent`. Fixes #32 indirectly
 
 1.3.0 - Fixed support for fractional differences via @jacobp100 in #29

README.md

@@ -48,6 +48,37 @@ Create an differential image between multiple images
         - For example, if an image is `+` and we diff with `-`, then the image will have `|` be red but also contain a faded `-`
         - By default, this options is `false` meaning a shadow will not be drawn
 
+### CLI usage
+We offer an `image-diff` executable to diff from the CLI. When images match, its exit code will be `0`. When they don't match, then it will be non-zero (e.g. `1`).
+
+```
+$ image-diff --help
+
+  Usage: image-diff [options] <actual-image> <expected-image> [diff-image]
+
+  Options:
+
+    -h, --help     output usage information
+    -V, --version  output the version number
+    --shadow       Draw a shadow of unchanges parts on diff image
+
+```
+
+Example usage:
+
+```bash
+# Images don't match
+image-diff checkerboard.png white.png diff.png
+echo $?
+# 1
+# We can look at `diff.png` for the diff result
+
+# Images do match
+image-diff checkerboard.png white.png
+echo $?
+# 0
+```
+
 ## Contributing
 In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint via [grunt](https://github.com/gruntjs/grunt) and test via `npm test`.
 

bin/image-diff

@@ -0,0 +1,39 @@
+#!/usr/bin/env node
+// Load in our dependencies
+var program = require('commander');
+var pkg = require('../package.json');
+var imageDiff = require('../');
+
+// Configure our CLI
+program.name = pkg.name;
+program
+  .version(pkg.version)
+  .usage('[options] <actual-image> <expected-image> [diff-image]')
+  .option('--shadow', 'Draw a shadow of unchanges parts on diff image')
+  .action(function handleRun (actualImage, expectedImage, diffImage, program) {
+    // If there is no program, then assume diffImage was left out
+    if (program === undefined) {
+      program = diffImage;
+      diffImage = undefined;
+    }
+
+    // Run our diff
+    imageDiff({
+      actualImage: actualImage,
+      diffImage: diffImage,
+      expectedImage: expectedImage,
+      shadow: program.shadow
+    }, function handleImageDiff (err, imagesAreSame) {
+      // If there was an error, throw it
+      if (err) {
+        throw err;
+      }
+
+      // Otherwise, exit based on the result
+      var exitCode = imagesAreSame ? 0 : 1;
+      process.exit(exitCode);
+    });
+  });
+
+// Parse our CLI arguments
+program.parse(process.argv);

package.json

@@ -21,6 +21,9 @@
       "url": "https://github.com/uber/image-diff/blob/master/LICENSE-MIT"
     }
   ],
+  "bin": {
+    "image-diff": "bin/image-diff"
+  },
   "main": "lib/image-diff",
   "engines": {
     "node": ">= 0.8.0"
@@ -31,6 +34,7 @@
   "dependencies": {
     "async": "~0.2.9",
     "buffered-spawn": "~1.1.1",
+    "commander": "~2.9.0",
     "gm": "~1.13.3",
     "mkdirp": "~0.3.5",
     "tmp": "0.0.23"