更新

TongjiUniApp/node_modules/@jimp/plugin-normalize/src/index.js

@@ -0,0 +1,86 @@
+import { isNodePattern } from '@jimp/utils';
+
+/**
+ * Get an image's histogram
+ * @return {object} An object with an array of color occurrence counts for each channel (r,g,b)
+ */
+function histogram() {
+  const histogram = {
+    r: new Array(256).fill(0),
+    g: new Array(256).fill(0),
+    b: new Array(256).fill(0)
+  };
+
+  this.scanQuiet(0, 0, this.bitmap.width, this.bitmap.height, function(
+    x,
+    y,
+    index
+  ) {
+    histogram.r[this.bitmap.data[index + 0]]++;
+    histogram.g[this.bitmap.data[index + 1]]++;
+    histogram.b[this.bitmap.data[index + 2]]++;
+  });
+
+  return histogram;
+}
+
+/**
+ * Normalize values
+ * @param  {integer} value Pixel channel value.
+ * @param  {integer} min   Minimum value for channel
+ * @param  {integer} max   Maximum value for channel
+ * @return {integer} normalized values
+ */
+const normalize = function(value, min, max) {
+  return ((value - min) * 255) / (max - min);
+};
+
+const getBounds = function(histogramChannel) {
+  return [
+    histogramChannel.findIndex(value => value > 0),
+    255 -
+      histogramChannel
+        .slice()
+        .reverse()
+        .findIndex(value => value > 0)
+  ];
+};
+
+/**
+ * Normalizes the image
+ * @param {function(Error, Jimp)} cb (optional) a callback for when complete
+ * @returns {Jimp} this for chaining of methods
+ */
+export default () => ({
+  normalize(cb) {
+    const h = histogram.call(this);
+
+    // store bounds (minimum and maximum values)
+    const bounds = {
+      r: getBounds(h.r),
+      g: getBounds(h.g),
+      b: getBounds(h.b)
+    };
+
+    // apply value transformations
+    this.scanQuiet(0, 0, this.bitmap.width, this.bitmap.height, function(
+      x,
+      y,
+      idx
+    ) {
+      const r = this.bitmap.data[idx + 0];
+      const g = this.bitmap.data[idx + 1];
+      const b = this.bitmap.data[idx + 2];
+
+      this.bitmap.data[idx + 0] = normalize(r, bounds.r[0], bounds.r[1]);
+      this.bitmap.data[idx + 1] = normalize(g, bounds.g[0], bounds.g[1]);
+      this.bitmap.data[idx + 2] = normalize(b, bounds.b[0], bounds.b[1]);
+    });
+
+    if (isNodePattern(cb)) {
+      cb.call(this, null, this);
+    }
+
+    return this;
+  }
+});