feat: accept promise-based transform function

package.json

@@ -48,6 +48,7 @@
     "splash screen"
   ],
   "dependencies": {
+    "@ionic/utils-array": "^2.1.1",
     "@ionic/utils-fs": "^3.0.0",
     "debug": "^4.1.1",
     "elementtree": "^0.1.7",

src/image.ts

@@ -1,3 +1,4 @@
+import { reduce } from '@ionic/utils-array';
 import { readFile, writeFile } from '@ionic/utils-fs';
 import Debug from 'debug';
 import sharp, { Metadata, Sharp } from 'sharp';
@@ -20,7 +21,7 @@ import {
 
 const debug = Debug('cordova-res:image');
 
-export type SharpTransformation = (pipeline: Sharp) => Sharp;
+export type SharpTransformation = (pipeline: Sharp) => Promise<Sharp> | Sharp;
 
 /**
  * Check an array of source files, returning the first viable image.
@@ -207,20 +208,21 @@ export async function generateImage(
     );
   }
 
-  const pipeline = applyTransformations(src, [
+  const pipeline = await applyTransformations(src, [
     createImageResizer(image),
     createImageConverter(image.format),
   ]);
 
   await writeFile(image.src, await pipeline.toBuffer());
 }
 
-export function applyTransformations(
+export async function applyTransformations(
   src: Sharp,
   transformations: readonly SharpTransformation[],
-): Sharp {
-  return transformations.reduce(
-    (pipeline, transformation) => transformation(pipeline),
+): Promise<Sharp> {
+  return reduce(
+    transformations,
+    async (pipeline, transformation) => transformation(pipeline),
     src,
   );
 }

src/index.ts

@@ -19,6 +19,7 @@ import {
   PLATFORMS,
   Platform,
   RunPlatformOptions,
+  TransformFunction,
   prettyPlatform,
   run as runPlatform,
 } from './platform';
@@ -197,7 +198,7 @@ namespace CordovaRes {
      *
      * @returns Sharp object
      */
-    readonly transform?: (image: ImageSchema, pipeline: Sharp) => Sharp;
+    readonly transform?: TransformFunction;
   };
 
   /**

src/platform.ts

@@ -49,7 +49,10 @@ export interface AndroidAdaptiveIconResourcePart {
   readonly [ResourceKey.SRC]: string;
 }
 
-export type TransformFunction = (image: ImageSchema, pipeline: Sharp) => Sharp;
+export type TransformFunction = (
+  image: ImageSchema,
+  pipeline: Sharp,
+) => Promise<Sharp> | Sharp;
 
 export interface ResourceOptions<S> {
   /**
@@ -291,17 +294,19 @@ export function getResourceTransformFunction(
 export function combineTransformFunctions(
   transformations: readonly TransformFunction[],
 ): TransformFunction {
-  return transformations.reduce((acc, transformation) => (image, pipeline) => {
-    const result = acc(image, pipeline);
+  return transformations.reduce(
+    (acc, transformation) => async (image, pipeline) => {
+      const result = await acc(image, pipeline);
 
-    if (!result || typeof result !== 'object') {
-      throw new BadInputError(
-        `Invalid Sharp pipeline returned while performing transforms: ${result}`,
-      );
-    }
+      if (!result || typeof result !== 'object') {
+        throw new BadInputError(
+          `Invalid Sharp pipeline returned while performing transforms: ${result}`,
+        );
+      }
 
-    return transformation(image, result);
-  });
+      return transformation(image, result);
+    },
+  );
 }
 
 /**
@@ -553,7 +558,7 @@ export async function generateImageResource(
 
   await ensureDir(pathlib.dirname(dest));
 
-  const img = transform(generatedImage, pipeline.clone());
+  const img = await transform(generatedImage, pipeline.clone());
 
   await generateImage(generatedImage, img, metadata, errstream);