From db63a70c8a2fd9899e7465cd4aa633ecab4348b3 Mon Sep 17 00:00:00 2001
From: Vladimir Mandic <mandic00@live.com>
Date: Fri, 5 Nov 2021 15:09:54 -0400
Subject: [PATCH] add histogram equalization

---
 TODO.md                    |  6 ++----
 demo/typescript/index.html |  1 +
 src/config.ts              |  9 +++++++--
 src/image/enhance.ts       | 20 ++++++++++++++++++++
 src/image/image.ts         |  3 ++-
 wiki                       |  2 +-
 6 files changed, 33 insertions(+), 8 deletions(-)
 create mode 100644 src/image/enhance.ts

diff --git a/TODO.md b/TODO.md
index b0ccdfd3..41260b76 100644
--- a/TODO.md
+++ b/TODO.md
@@ -2,17 +2,15 @@
 
 ## Work in Progress
 
-- Switch to custom `tfjs` for main `human` ESM bundle
-- Sort out incompatibility with latest `long.js` 5.0.0 due to CJS to ESM switch
-
 <br>
 
 ### Exploring
 
 - Optical Flow: <https://docs.opencv.org/3.3.1/db/d7f/tutorial_js_lucas_kanade.html>
-- Histogram Equalization: Regular, Adaptive, Contrast Limited
+- Histogram Equalization: Regular, Adaptive, Contrast Limited, CLAHE
 - TFLite Models: <https://js.tensorflow.org/api_tflite/0.0.1-alpha.4/>
 - Body segmentation: `robust-video-matting`
+- TFJS incompatibility with latest `long.js` 5.0.0 due to CJS to ESM switch
 
 <br><hr><br>
 
diff --git a/demo/typescript/index.html b/demo/typescript/index.html
index a74a14bc..3b7d0ba4 100644
--- a/demo/typescript/index.html
+++ b/demo/typescript/index.html
@@ -26,5 +26,6 @@
     <pre id="status" style="position: absolute; top: 12px; right: 20px; background-color: grey; padding: 8px; box-shadow: 2px 2px black"></pre>
     <pre id="log" style="padding: 8px"></pre>
     <div id="performance" style="position: absolute; bottom: 0; width: 100%; padding: 8px; font-size: 0.8rem;"></div>
+    <canvas id="test" style="position: absolute; bottom: 0; right: 0; width: 30%"></canvas>
   </body>
 </html>
diff --git a/src/config.ts b/src/config.ts
index 502b1ae8..e89c9601 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -122,16 +122,20 @@ export interface SegmentationConfig extends GenericConfig {
 export interface FilterConfig {
   /** @property are image filters enabled? */
   enabled: boolean,
-  /** Resize input width
+  /** @property perform image histogram equalization */
+  equalization: boolean,
+  /** resize input width
   * - if both width and height are set to 0, there is no resizing
   * - if just one is set, second one is scaled automatically
   * - if both are set, values are used as-is
+  * @property
   */
   width: number,
-  /** Resize input height
+  /** resize input height
   * - if both width and height are set to 0, there is no resizing
   * - if just one is set, second one is scaled automatically
   * - if both are set, values are used as-is
+  * @property
   */
   height: number,
   /** @property return processed canvas imagedata in result */
@@ -262,6 +266,7 @@ const config: Config = {
   skipAllowed: false,
   filter: {
     enabled: true,
+    equalization: false,
     width: 0,
     height: 0,
     flip: false,
diff --git a/src/image/enhance.ts b/src/image/enhance.ts
new file mode 100644
index 00000000..8fb55782
--- /dev/null
+++ b/src/image/enhance.ts
@@ -0,0 +1,20 @@
+/**
+ * Image enhancements
+ */
+
+import * as tf from '../../dist/tfjs.esm.js';
+import type { Tensor } from '../exports';
+
+export function histogramEqualization(input: Tensor): Tensor {
+  const channels = tf.split(input, 3, 2);
+  const min: Tensor[] = [tf.min(channels[0]), tf.min(channels[1]), tf.min(channels[2])];
+  const max: Tensor[] = [tf.max(channels[0]), tf.max(channels[1]), tf.max(channels[2])];
+  const sub = [tf.sub(channels[0], min[0]), tf.sub(channels[1], min[1]), tf.sub(channels[2], min[2])];
+  const range = [tf.sub(max[0], min[0]), tf.sub(max[1], min[1]), tf.sub(max[2], min[2])];
+  const fact = [tf.div(255, range[0]), tf.div(255, range[1]), tf.div(255, range[2])];
+  const enh = [tf.mul(sub[0], fact[0]), tf.mul(sub[1], fact[1]), tf.mul(sub[2], fact[2])];
+  const rgb = tf.stack([enh[0], enh[1], enh[2]], 2);
+  const reshape = tf.reshape(rgb, [1, input.shape[0], input.shape[1], 3]);
+  tf.dispose([...channels, ...min, ...max, ...sub, ...range, ...fact, ...enh, rgb]);
+  return reshape;
+}
diff --git a/src/image/image.ts b/src/image/image.ts
index 97330b40..ad8f53b6 100644
--- a/src/image/image.ts
+++ b/src/image/image.ts
@@ -7,6 +7,7 @@ import * as fxImage from './imagefx';
 import type { Input, AnyCanvas, Tensor, Config } from '../exports';
 import { env } from '../util/env';
 import { log, now } from '../util/util';
+import * as enhance from './enhance';
 
 const maxSize = 2048;
 // internal temp canvases
@@ -201,7 +202,7 @@ export function process(input: Input, config: Config, getTensor: boolean = true)
     }
     if (!pixels) throw new Error('cannot create tensor from input');
     const casted = tf.cast(pixels, 'float32');
-    const tensor = tf.expandDims(casted, 0);
+    const tensor = config.filter.equalization ? enhance.histogramEqualization(casted) : tf.expandDims(casted, 0);
     tf.dispose([pixels, casted]);
     return { tensor, canvas: (config.filter.return ? outCanvas : null) };
   }
diff --git a/wiki b/wiki
index 5e89af10..6abe315e 160000
--- a/wiki
+++ b/wiki
@@ -1 +1 @@
-Subproject commit 5e89af1004860ea9f302e516699b5e0b4e0a825f
+Subproject commit 6abe315e2ae3e3aa457c4c728d9e2959d7e023db