Add contrast limiting adaptive histogram equalization (CLAHE) operator (#2726)

test/fixtures/index.js

@@ -121,6 +121,8 @@ module.exports = {
 
   inputV: getPath('vfile.v'),
 
+  inputJpgClahe: getPath('concert.jpg'), // public domain - https://www.flickr.com/photos/mars_/14389236779/
+
   testPattern: getPath('test-pattern.png'),
 
   // Path for tests requiring human inspection

test/unit/clahe.js

@@ -0,0 +1,139 @@
+'use strict';
+
+const assert = require('assert');
+
+const sharp = require('../../lib');
+const fixtures = require('../fixtures');
+
+describe('Clahe', function () {
+  it('width 5 width 5 maxSlope 0', function (done) {
+    sharp(fixtures.inputJpgClahe)
+      .clahe({ width: 5, height: 5, maxSlope: 0 })
+      .toBuffer(function (err, data, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        fixtures.assertSimilar(fixtures.expected('clahe-5-5-0.jpg'), data, { threshold: 10 }, done);
+      });
+  });
+
+  it('width 5 width 5 maxSlope 5', function (done) {
+    sharp(fixtures.inputJpgClahe)
+      .clahe({ width: 5, height: 5, maxSlope: 5 })
+      .toBuffer(function (err, data, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        fixtures.assertSimilar(fixtures.expected('clahe-5-5-5.jpg'), data, done);
+      });
+  });
+
+  it('width 11 width 25 maxSlope 14', function (done) {
+    sharp(fixtures.inputJpgClahe)
+      .clahe({ width: 11, height: 25, maxSlope: 14 })
+      .toBuffer(function (err, data, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        fixtures.assertSimilar(fixtures.expected('clahe-11-25-14.jpg'), data, done);
+      });
+  });
+
+  it('width 50 width 50 maxSlope 0', function (done) {
+    sharp(fixtures.inputJpgClahe)
+      .clahe({ width: 50, height: 50, maxSlope: 0 })
+      .toBuffer(function (err, data, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        fixtures.assertSimilar(fixtures.expected('clahe-50-50-0.jpg'), data, done);
+      });
+  });
+
+  it('width 50 width 50 maxSlope 14', function (done) {
+    sharp(fixtures.inputJpgClahe)
+      .clahe({ width: 50, height: 50, maxSlope: 14 })
+      .toBuffer(function (err, data, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        fixtures.assertSimilar(fixtures.expected('clahe-50-50-14.jpg'), data, done);
+      });
+  });
+
+  it('width 100 width 50 maxSlope 3', function (done) {
+    sharp(fixtures.inputJpgClahe)
+      .clahe({ width: 100, height: 50, maxSlope: 3 })
+      .toBuffer(function (err, data, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        fixtures.assertSimilar(fixtures.expected('clahe-100-50-3.jpg'), data, done);
+      });
+  });
+
+  it('width 100 width 100 maxSlope 0', function (done) {
+    sharp(fixtures.inputJpgClahe)
+      .clahe({ width: 100, height: 100, maxSlope: 0 })
+      .toBuffer(function (err, data, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        fixtures.assertSimilar(fixtures.expected('clahe-100-100-0.jpg'), data, done);
+      });
+  });
+
+  it('invalid maxSlope', function () {
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: 100, height: 100, maxSlope: -5 });
+    });
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: 100, height: 100, maxSlope: 110 });
+    });
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: 100, height: 100, maxSlope: 5.5 });
+    });
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: 100, height: 100, maxSlope: 'a string' });
+    });
+  });
+
+  it('invalid width', function () {
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: 100.5, height: 100 });
+    });
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: -5, height: 100 });
+    });
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: true, height: 100 });
+    });
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: 'string test', height: 100 });
+    });
+  });
+
+  it('invalid height', function () {
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: 100, height: 100.5 });
+    });
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: 100, height: -5 });
+    });
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: 100, height: true });
+    });
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe({ width: 100, height: 'string test' });
+    });
+  });
+
+  it('invalid options object', function () {
+    assert.throws(function () {
+      sharp(fixtures.inputJpgClahe).clahe(100, 100, 5);
+    });
+  });
+
+  it('uses default maxSlope of 3', function (done) {
+    sharp(fixtures.inputJpgClahe)
+      .clahe({ width: 100, height: 50 })
+      .toBuffer(function (err, data, info) {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        fixtures.assertSimilar(fixtures.expected('clahe-100-50-3.jpg'), data, done);
+      });
+  });
+});