I noticed that using transparency in a picture that's compiled as vector graphic output (render=0, no PRC) leads to strange colors (they look paler and desaturated) when the resulting picture is viewed with Adobe Acrobat (I use version X). When I view the output PDF with SumatraPDF everything looks fine. An Example:
size(10cm,0); path cle=unitcircle; draw((-2.5,0)--(2.5,0),linewidth(10mm)); filldraw(shift((-1.5,0))*cle,magenta+opacity(.5)); filldraw(shift((-0.5,0))*cle,green+opacity(.5)); filldraw(shift((0.5,0))*cle,red+opacity(.5)); filldraw(shift((1.5,0))*cle,blue+opacity(.5)); shipout(format="pdf");
On the left hand side you see the picture viewed with Adobe Acrobat and on the right hand side you see the picture viewed with SumatraPDF.
When I leave out the opacity settings everything looks fine:
I encountered such an issue before when using opacity in a picture created by TikZ and think the problem might be connected to that (There seems to be some trouble with transparency groups in Adobe Acrobat). Here is a way to solve this problem in a TikZ picture. How can the coloring issue be solved in Asymptote?