I exported a long PDF page at 300 DPI and got 131: the WebP 16383 cap

Testing with ImgIng on an Apple M4 Mac reveals that the WebP format has a hard size ceiling of 16383 pixels because width and height are stored in 14 bits. When exporting long PDF pages at 144, 216, or 300 DPI, the resulting files remained byte-for-byte identical at 1456×16380. Pillow 11.3 confirms this limit, refusing images at 16384 pixels. Splitting multi-page PDFs into several long images is more effective than lowering the DPI.