How to accelerate exporting of multiple layers to PNG-File?

Question

Hello,
ai::int32 aint;
sAILayer->CountLayers(&aint);
for (int i = 0; i < (int) aint; i++){
      sAILayer->GetNthLayer((ai::int32) i,&layer);
      artSetSuite->LayerArtSet(layer, artSet);
AIArtHandle hand;
sAIArt->GetFirstArtOfLayer(layer, &hand);
e2 = sAIRasterize->Rasterize(artSet, &rs, &bounds, kPlaceAboveAll, hand, &art, MyRasterizeProgressProc);
sAILayer->GetFirstLayer(&layer);
e2 = sAIArt->GetLayerOfArt(art, &layer);
e2 = sAIArt->GetFirstArtOfLayer(layer, &art);
error = sAIImageOptSuite->MakePNG24(art, dstfilter, pngParams2, MyRasterizeProgressProc);
the code above shows how I managed to export a artboard with all layers to PNG-File. My question is, if there is a faster way to combine all layer before exporting, maybe a way without the "temporary layer" (Rasterize(...)-method)?
When I export with the standard-export-button in Adobe Illustrator, it runs fast and with all layers.
I hope you can help me.
Greatings from Germany, Dortmund

Answer 1

I'm confused. The code you quoted almost does exactly what I'd suggest, though the opening loop is odd. It seems to get each layer's artset and then do nothing with it (well, the last one would be rasterized). Why aren't you using AIArtSetSuite::UnionArtSet() to combine all the layer art sets into one art set and then rasterizing that? Then I'd make a PNG from the resultant kRasterArt just like you're doing.
I"m also not sure what you mean by 'temporary layer' -- you don't seem to be creating a temporary layer. A temporary raster object, sure, but I suspect that's unavoidable.