Add trim operation to remove "boring" edges (#491 #492)

test/unit/trim.js

@@ -0,0 +1,39 @@
+'use strict';
+
+var assert = require('assert');
+
+var sharp = require('../../index');
+var fixtures = require('../fixtures');
+
+describe('Trim borders', function() {
+
+  it('Threshold default', function(done) {
+    var expected = fixtures.expected('alpha-layer-1-fill-trim-resize.png');
+    sharp(fixtures.inputPngOverlayLayer1)
+      .resize(450, 322)
+      .trim()
+      .toBuffer(function(err, data, info) {
+        if (err) throw err;
+        assert.strictEqual('png', info.format);
+        assert.strictEqual(450, info.width);
+        assert.strictEqual(322, info.height);
+        fixtures.assertSimilar(expected, data, done);
+      });
+  });
+
+  it('16-bit PNG with alpha channel', function(done) {
+    sharp(fixtures.inputPngWithTransparency16bit)
+      .resize(32, 32)
+      .trim()
+      .toBuffer(function(err, data, info) {
+        if (err) throw err;
+        assert.strictEqual(true, data.length > 0);
+        assert.strictEqual('png', info.format);
+        assert.strictEqual(32, info.width);
+        assert.strictEqual(32, info.height);
+        assert.strictEqual(4, info.channels);
+        fixtures.assertSimilar(fixtures.expected('trim-16bit-rgba.png'), data, done);
+      });
+  });
+
+});