Flatten Transparency creates huge file that is difficult to process

[Avatar Lucas]

Hi,

I am having a lot of problems with the Flatten Transparency command on an illustrator file.

I am using a: Dell Alienware i7-9750H with 32GB Ram, virtual memory of 40GB, free disk space of 90GB and a NVIDIA GeForce RTX 2060 running on Windows 10 64-bit and Illustrator CC.

I have been working on an architectural drawing that has some 9 overlapping layers - the main top layer being black lines for the building and then subsequent layers displaying different conditions that have generally a single color line and filled with a tiled red and white pattern or black and white or turquoise and white etc. The file itself is only 3MB large.

I have not had any problems working with the file, but after creating a 743KB PDF file heard it was taking an inordinately long time to flatten and print. I therefore attempted to use FLATTEN TRANSPARENCY and problems emerged immediately. After numerous crashes, I finally managed to flatten the image and it created a monster 444MB file. I do not understand why flattening all the transparent overlapping layers would make a file that is 100x larger.

I am adding an example of the image here:

[Ton Frederiks]

Flatten transparency can make huge files when the Raster/Vector Balance is high.

https://helpx.adobe.com/acrobat/using/transparency-flattening-acrobat-pro.html

Your pattern fills look like the contain many tiny squares. As long as they are patterns they do not take up very much space, the fill refers to a single pattern tile that is repeated. If that pattern fill is combined with transparency and flattened it will create many tiny squares.

I wonder if it is necessary to use patterns instead of a flat fill color, it certainly will make the file smaller after flattening.

[Kurt Gold]

This monster is not normal.

Can you share the original file (before any kind of flattening), so one may take a look at it?

[Ton Frederiks]

Does not have to be the whole monster, a little bit (with a pattern and transparent area) will do.

You can check which areas will be affected with the Window menu > Flattener Preview panel.

[Avatar Lucas]

Ton, you were right. The chequered pattern was the issue and when I changed to a 50% opaque single color there were no more problems. Seems strange that Illustrator would have such an issue with a basic white and colored pattern but it does.

[Ton Frederiks]

Good to hear that helped.

A pattern is very efficient. It is defined once and every time it is used it only points to that same  definition. Flattening creates many separate instances of that pattern.