Expose libvips recombination matrix operation #1477

lib/operation.js

@@ -378,6 +378,43 @@ function linear (a, b) {
   return this;
 }
 
+/**
+ * Recomb the image with the specified matrix.
+ *
+ * @example
+ * sharp(input)
+ *   .recomb([
+ *    [0.3588, 0.7044, 0.1368],
+ *    [0.2990, 0.5870, 0.1140],
+ *    [0.2392, 0.4696, 0.0912],
+ *   ])
+ *   .raw()
+ *   .toBuffer(function(err, data, info) {
+ *     // data contains the raw pixel data after applying the recomb
+ *     // With this example input, a sepia filter has been applied
+ *   });
+ *
+ * @param {Array<Array<Number>>} 3x3 Recombination matrix
+ * @returns {Sharp}
+ * @throws {Error} Invalid parameters
+ */
+function recomb (inputMatrix) {
+  if (!Array.isArray(inputMatrix) || inputMatrix.length !== 3 ||
+      inputMatrix[0].length !== 3 ||
+      inputMatrix[1].length !== 3 ||
+      inputMatrix[2].length !== 3
+  ) {
+    // must pass in a kernel
+    throw new Error('Invalid Recomb Matrix');
+  }
+  this.options.recombMatrix = [
+    inputMatrix[0][0], inputMatrix[0][1], inputMatrix[0][2],
+    inputMatrix[1][0], inputMatrix[1][1], inputMatrix[1][2],
+    inputMatrix[2][0], inputMatrix[2][1], inputMatrix[2][2]
+  ].map(Number);
+  return this;
+}
+
 /**
  * Decorate the Sharp prototype with operation-related functions.
  * @private
@@ -398,6 +435,7 @@ module.exports = function (Sharp) {
     convolve,
     threshold,
     boolean,
-    linear
+    linear,
+    recomb
   });
 };