By transfering `ArrayBuffer`s you can avoid having two copies of the same data, i.e. one copy on each of the worker/main-thread, for data that's used only *once* on the worker-thread.
Note how the code in [`PDFImage.createMask`](80135378ca/src/core/image.js (L284-L285)) goes to great lengths to actually enable tranfering of the image data. However in [`PartialEvaluator.buildPaintImageXObject`](80135378ca/src/core/evaluator.js (L336)) the `cached` property is always set to `true`, which disqualifies the image data from being transfered; see [`getTransfers`](80135378ca/src/core/operator_list.js (L552-L554)).
For most ImageMask data this patch won't matter, since images found in the `/Resources -> /XObject` dictionary will always be indexed by name. However for *inline* images which contains ImageMask data, where only "small" images are cached (in both `parser.js` and `evaluator.js`), the current code will result in some unnecessary memory usage.
7273795eb6