ndvi, modularized PixelManipulation

src/modules/PixelManipulation.js

@@ -0,0 +1,61 @@
+/*
+ * General purpose per-pixel manipulation
+ * accepting a changePixel() method to remix a pixel's channels
+ */
+module.exports = function PixelManipulation(image, options) {
+
+  options = options || {};
+  options.changePixel = options.changePixel || function changePixel(r, g, b, a) {
+    return [r, g, b, a];
+  }
+  options.format = options.format || "jpg";
+
+  var getPixels = require("get-pixels"),
+      savePixels = require("save-pixels"),
+      base64 = require('base64-stream');
+
+  getPixels(image.src, function(err, pixels) {
+
+    if(err) {
+      console.log("Bad image path")
+      return
+    }
+
+    // iterate through pixels;
+    // this could possibly be more efficient; see 
+    // https://github.com/p-v-o-s/infragram-js/blob/master/public/infragram.js#L173-L181
+    for(var x = 1; x < pixels.shape[0]; x++) {
+      for(var y = 1; y < pixels.shape[1]; y++) {
+
+        pixel = options.changePixel(
+          pixels.get(x, y, 0),
+          pixels.get(x, y, 1),
+          pixels.get(x, y, 2),
+          pixels.get(x, y, 3)
+        );
+
+        pixels.set(x, y, 0, pixel[0]);
+        pixels.set(x, y, 1, pixel[1]);
+        pixels.set(x, y, 2, pixel[2]);
+        pixels.set(x, y, 3, pixel[3]);
+
+      }
+    }
+
+    // there may be a more efficient means to encode an image object,
+    // but node modules and their documentation are essentially arcane on this point
+    var buffer = base64.encode();
+    savePixels(pixels, options.format)
+      .on('end', function() {
+
+      var image = new Image();
+
+      if (options.onComplete) options.onComplete(image);
+
+      image.src = 'data:image/' + options.format + ';base64,' + buffer.read().toString();
+
+    }).pipe(buffer);
+
+  });
+
+}