Expose GIF opts: interFrameMaxError, interPaletteMaxError #3401

docs/api-output.md

@@ -334,6 +334,8 @@ The palette of the input image will be re-used if possible.
     *   `options.colors` **[number][12]** alternative spelling of `options.colours` (optional, default `256`)
     *   `options.effort` **[number][12]** CPU effort, between 1 (fastest) and 10 (slowest) (optional, default `7`)
     *   `options.dither` **[number][12]** level of Floyd-Steinberg error diffusion, between 0 (least) and 1 (most) (optional, default `1.0`)
+    *   `options.interFrameMaxError` **[number][12]** maximum inter-frame error for transparency, between 0 (lossless) and 32 (optional, default `0`)
+    *   `options.interPaletteMaxError` **[number][12]** maximum inter-palette error for palette reuse, between 0 and 256 (optional, default `3`)
     *   `options.loop` **[number][12]** number of animation iterations, use 0 for infinite animation (optional, default `0`)
     *   `options.delay` **([number][12] | [Array][13]<[number][12]>)?** delay(s) between animation frames (in milliseconds)
     *   `options.force` **[boolean][10]** force GIF output, otherwise attempt to use input format (optional, default `true`)
@@ -361,6 +363,13 @@ const out = await sharp('in.gif', { animated: true })
   .toBuffer();
 ```
 
+```javascript
+// Lossy file size reduction of animated GIF
+await sharp('in.gif', { animated: true })
+  .gif({ interFrameMaxError: 8 })
+  .toFile('optim.gif');
+```
+
 *   Throws **[Error][4]** Invalid options
 
 Returns **Sharp**&#x20;

docs/changelog.md

@@ -6,6 +6,9 @@ Requires libvips v8.13.3
 
 ### v0.31.3 - TBD
 
+* Expose `interFrameMaxError` and `interPaletteMaxError` GIF optimisation properties.
+  [#3401](https://github.com/lovell/sharp/issues/3401)
+
 * Prevent possible race condition awaiting metadata of Stream-based input.
   [#3451](https://github.com/lovell/sharp/issues/3451)