|
From: George <geo...@ho...> - 2008-05-16 08:19:14
|
Hi all, another simple question (I hope). In principal this has to do with the best approach to my task. I need to render groups of vectors (for a map) in different layers. The order is important and so is speed. Currently I am running through each "layer" and rendering its contents is particular order, however, as I cannot cache all the data to be rendered into memory (too much) I need to sequentially read vector by vector from the source and then discard. This makes it considerably slow because in essence I need to read each layer data from the source 2-3 times, one for the geometry itself (bottom-up), one for the labels (top-down) and if a line layer (road) another one for the outline (bottom-up). The 3rd one is tricky (which actually happens first) cause I wish to group outlines between layers so all outlines for all road categories to be rendered together and then the actual road color/fill. My current thought now is to work on a image-layered approach as Photoshop does, where I read the data once but I can draw onto different pixmaps and in the end combine them keeping their Alpha transparency. Would you say this is a good/fast approach to my problem and can I expect the same high quality image by doing copy_from ? Thanks George |