100 scaled image => OutOfMemory

Since I upgraded my wiki from 8.1 to 11.8.1, the slide-show-of-photo pages create an OutOfMemory. The reason is an OOM: java.awt.image.DataBufferByte.<init>(DataBufferByte.java:92) called by DefaultImageProcessor.readImage(DefaultImageProcessor.java:58).

The slide-show-of-photo page is simply a gallery made of all relevant photos (typical 300-400) all scaled down to 1024 width. It is generated by a little velocity which calls `[[image:$attachment.filename||width=1024]]`

I've tried to explore the memory usage based on the max number of scaled pictures and it seems to be at about 100 that my max 2500 MB heap size is reached. There must be a leak and also there seems to be a missing caching for the attachments' downloads of pictures. (a caching would create no effect if downloading again the same images).