The white lines are a transparency flattening artifact called stitching. Instead of printing to PDF, EXPORT to PDF and use Acrobat 5 or higher compatibility, which will leave the transparency live and eliminate the stitching artifacts.
Wow, that did it.
Thank you very much!
will the stitching appear when I print? I just finished a 100+ page book for a client (using the Blurb book creator plug-in) and all of my placed photoshop files have this thin "stitching" line around them. deadline is today, ack.
There's a pretty good chance it will. As far as I know Blurb uses digital printing, not high-res offset. Ask for a sample, and see if there's any way they can handle PDF with live transparency instead.
They may or may not appear, depending on the process further downstream. When the file is 'printed' to PDF, or exported to PDF below level 1.4, the resulting file is flattened during output. Using both methods, you can determine the 'Transparency Flattener' settings in the 'Advanced' section of the the Print Dialogue or Export Dialogue. Choosing 'High Resolution' will set vector flattening to 2400 dpi.
If your printer then RIPs the resulting files at 2400 dpi, then your stitching lines will be only 1 pixel wide at 2400 dpi, i.e. almost microscopic. Depending on the colours involved and the print process/quality, they may not be visible in the finished product.
You can test, to a certain extent, how visible the stitching lines are once RIPped by taking one of your final PDFs and opening it in Photoshop at the same resolution that the file will be RIPped at by your printer. This will rasterise your PDF and mimic one aspect of what a RIP will do. Don't forget that there is also a screening process which will may have a further effect.
Hope this helps.
found this in the blurb faq: "if you turn OFF the "Smooth Line Art" in Acrobat Preferences, the lines should disappear."
they also say: "Note: If the lines do not disappear when the above option is OFF they may appear in the printed book.