Expose optional minAmplitude parameter of blur operation (#4172)

lib/constructor.js

@@ -227,6 +227,7 @@ const Sharp = function (input, options) {
     medianSize: 0,
     blurSigma: 0,
     precision: 'integer',
+    minAmpl: 0.2,
     sharpenSigma: 0,
     sharpenM1: 1,
     sharpenM2: 2,

lib/index.d.ts

@@ -1347,6 +1347,8 @@ declare namespace sharp {
     interface BlurOptions {
         /** A value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2` */
         sigma: number;
+        /** A value between 0.001 and 1. A smaller value will generate a larger, more accurate mask. */
+        minAmplitude?: number;
         /** How accurate the operation should be, one of: integer, float, approximate. (optional, default "integer") */
         precision?: Precision | undefined;
     }

lib/operation.js

@@ -381,6 +381,7 @@ function median (size) {
  * @param {Object|number|Boolean} [options]
  * @param {number} [options.sigma] a value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
  * @param {string} [options.precision='integer'] How accurate the operation should be, one of: integer, float, approximate.
+ * @param {number} [options.minAmplitude=0.2] A value between 0.001 and 1. A smaller value will generate a larger, more accurate mask.
  * @returns {Sharp}
  * @throws {Error} Invalid parameters
  */
@@ -400,6 +401,13 @@ function blur (options) {
         throw is.invalidParameterError('precision', 'one of: integer, float, approximate', options.precision);
       }
     }
+    if ('minAmplitude' in options) {
+      if (is.number(options.minAmplitude) && is.inRange(options.minAmplitude, 0.001, 1)) {
+        this.options.minAmpl = options.minAmplitude;
+      } else {
+        throw is.invalidParameterError('minAmplitude', 'number between 0.001 and 1', options.minAmplitude);
+      }
+    }
   }
 
   if (!is.defined(options)) {