Add abstract getter for default parameters.

source/gegl/base.ts

@@ -1,4 +1,6 @@
 export abstract class BaseOperation<P> {
+  public abstract get default(): P;
+
   public parameters: P;
 
   /**

source/gegl/crop.ts

@@ -17,6 +17,10 @@ export class Crop extends BaseOperation<CropParameters> {
     y: 0,
   };
 
+  public get default() {
+    return Crop.default;
+  }
+
   public appendCrop = false;
   public name = 'gegl:crop';
 

source/gegl/generic.ts

@@ -3,6 +3,10 @@ import {BaseOperation} from './base.js';
 export type GenericParameters = Record<string, number | string>;
 
 export class Generic extends BaseOperation<GenericParameters> {
+  public get default() {
+    return {};
+  }
+
   public appendCrop: boolean;
   public name: string;
 

source/gegl/mirrors.ts

@@ -33,6 +33,10 @@ export class Mirrors extends BaseOperation<MirrorsParameters> {
     warp: true,
   };
 
+  public get default() {
+    return Mirrors.default;
+  }
+
   public appendCrop = false;
   public name = 'gegl:mirrors';
 

source/gegl/newsprint.ts

@@ -45,6 +45,10 @@ export class Newsprint extends BaseOperation<NewsprintParameters> {
     turbulence: 0,
   };
 
+  public get default() {
+    return Newsprint.default;
+  }
+
   public appendCrop = false;
   public name = 'gegl:newsprint';
 

source/gegl/simplex-noise.ts

@@ -13,6 +13,10 @@ export class SimplexNoise extends BaseOperation<SimplexNoiseParameters> {
     seed: 1,
   };
 
+  public get default() {
+    return SimplexNoise.default;
+  }
+
   public appendCrop = true;
   public name = 'gegl:simplex-noise';