Why is it essential to flatten all figures and eliminate transparency?
Although you may be able to print a PDF containing multi-layer images on a desktop printer, or view it properly on a computer display, high speed printers such as those used to produce volumes of CinC have a strict upper bound on the time needed to rasterize each page, in order to keep paper flowing through the printers at a constant speed. The time needed to rasterize a multi-layer figure is proportional to the number of layers, which may be arbitrarily large. For this reason, these printers reject pages containing multiple layers. It is difficult or impossible to flatten multi-layer PDF files in a way that preserves the intended appearance. Usually the result is either a completely black rectangle in place of the figure, or a very blurry image with poor detail. For best results, the software used to create the figure should be used to flatten it, before including it in your manuscript. Eliminating transparency in figures is usually done by the same software used to flatten them. If t