Fixes #52 with transform function option.

package.json

@@ -53,6 +53,7 @@
     "@eslint/js": "^9.17.0",
     "ava": "^6.2.0",
     "eslint": "^9.17.0",
+    "exifr": "^7.1.3",
     "globals": "^15.14.0",
     "pixelmatch": "^5.3.0"
   },

src/global-options.js

@@ -61,9 +61,6 @@ const DEFAULTS = {
 
   fixOrientation: false, // always rotate images to ensure correct orientation
 
-  // Removed, no longer necessary in v6.0
-  // useCacheValidityInHash: true,
-
   // When the original width is smaller than the desired output width, this is the minimum size difference
   // between the next smallest image width that will generate one extra width in the output.
   // e.g. when using `widths: [400, 800]`, the source image would need to be at least (400 * 1.25 =) 500px wide
@@ -76,7 +73,11 @@ const DEFAULTS = {
   // writes to the file system and speeding up builds!
   transformOnRequest: false,
 
-  // v5 `extensions` was removed (option to override output format with new file extension), it wasn’t being used anywhere or documented
+  // operate on Sharp instance manually.
+  transform: undefined,
+
+  // v5.0.0 Removed `extensions`, option to override output format with new file extension. It wasn’t being used anywhere or documented.
+  // v6.0.0, removed `useCacheValidityInHash: true` see https://github.com/11ty/eleventy-img/issues/146#issuecomment-2555741376
 };
 
 function getGlobalOptions(eleventyConfig, options, via) {

src/image.js

@@ -120,7 +120,13 @@ class Image {
       opts.__originalSize = fs.statSync(this.src).size;
     }
 
-    return JSON.stringify(opts);
+    return JSON.stringify(opts, function(key, value) {
+      // allows `transform` functions to be truthy for in-memory key
+      if (typeof value === "function") {
+        return "<fn>";
+      }
+      return value;
+    });
   }
 
   getFileContents(overrideLocalFilePath) {
@@ -550,6 +556,15 @@ class Image {
         }
 
         let sharpInstance = sharpImage.clone();
+        let transform = this.options.transform;
+        if(transform) {
+          if(typeof transform !== "function") {
+            throw new Error("Expected `function` type in `transform` option. Received: " + transform);
+          }
+
+          await transform(sharpInstance);
+        }
+
         // Output images do not include orientation metadata (https://github.com/11ty/eleventy-img/issues/52)
         // Use sharp.rotate to bake orientation into the image (https://github.com/lovell/sharp/blob/v0.32.6/docs/api-operation.md#rotate):
         // > If no angle is provided, it is determined from the EXIF data. Mirroring is supported and may infer the use of a flip operation.

test/transform-hooks-test.js

@@ -0,0 +1,33 @@
+const test = require("ava");
+const exifr = require("exifr");
+
+const eleventyImage = require("../img.js");
+
+test("Transforms Empty", async t => {
+  let stats = await eleventyImage("./test/exif-sample-large.jpg", {
+    formats: ["auto"],
+    // transform: undefined,
+    dryRun: true,
+  });
+
+  let exif = await exifr.parse(stats.jpeg[0].buffer);
+  t.deepEqual(exif, undefined);
+});
+
+test("Transforms keep exif", async t => {
+  let stats = await eleventyImage("./test/exif-sample-large.jpg", {
+    formats: ["auto"],
+    // Keep exif metadata
+    transform: (sharp) => {
+      sharp.keepExif();
+    },
+    dryRun: true,
+  });
+
+  let exif = await exifr.parse(stats.jpeg[0].buffer);
+
+  t.is(Math.round(exif.latitude), 50);
+  t.is(Math.round(exif.longitude), 15);
+  t.is(exif.ApertureValue, 2);
+  t.is(exif.BrightnessValue, 9.38);
+});