Apply Pathfinder's boolean operations to multiple objects from a mask

[mjlcourier]

Hi, I work on large-format vector drawings that use traced and hand-drawn elements.

I would like to apply boolean operations aka Pathfinder operations such as Add, Subtract and Intersection to masses of traced vector objects in Illustrator. I don't mind if these objects need to be grouped first. But the numbers of objects involved means the operation needs to be automated.

My aim is to trim large numbers of traced objects to the outlines of masking objects drawn by me not the tracing algorithm.

Inkscape allows this to a limited exent with a script. The script throws errors and fails on large numbers of paths, unfortunately. It also layers tracings differently from either Trace Abutting or Trace Overlapping options in Illustrator.

I have learned Illustrator's highly unintuitive commands
Object > Expand (I think this means convert trace to paths)
and
Window > Pathfinder (I think this means boolean operations)
as well as the unclear distinction between
Open
and
Place
to put a bitmap on an Artboard.

I have then tried:

1

Image Trace
Expand
Draw the mask with Pen Tool
Object > Paths > Divide Objects Below
This only selects objects below my mask and frees them from the expanded group, rather than cut them to the path of the mask.

2

Image Trace
Expand
Draw the mask with Pen tool
Group the objects in the expanded/converted tracing
Window > Pathfinder > Intersection
This only returns an error about selecting two paths. I want the path of my mask to cut everything it touches and then leave me, in this case, with the intersection of the results.

Any help would be greatly appreciated.

Below is my preferred workflow visualised. I am usually working with expanded traces with hundreds or thousands of objects.

How I'd like to edit expanded Image Traces in Illustrator

[matthewn43692242]

The solution will depend on if you want permanent, destructive cutting or just masking. 

If you flatten (live paint or pathfinder) all the stuff you want to cut so there are no overlapping pieces you can cut a piece out pretty easy with the pathfinder. You could also use the pathfinders "divide" function to cut along all paths of all objects but then you'll have to delete all the throw-away pieces outside your shape somewhat manually... might be the fastest way though...

get all your background stuff, use divide, group it, put cutter/mask shape on top, divide again, delete outside parts. No too terrible.

Live paint would do close to the same thing in one shot but you still have to delete the unwanted parts manually.

What is your desired final output? print, vector file, image?

[mjlcourier]

That's very helpful. Final output is raster format. So both destructive and flattening operations are perfectly OK with me, in fact flattening is required for output. 

Divide gave two unexpected results:

A cut was successfully created along the masking path. A step in the right direction.

The masking shape seemed to get glued to the underlying shapes. Not good.

I've now used the almost identical icon to the icon for Pathfinder > Shape Modes > Intersect for the different command Pathfinder > Pathfinders > Crop. This gives me the result I want although it is destructive of the mask.

Thanks for pointing me in the right direction.

[mjlcourier]

It's great to find that I can crop the results of traces, but I've discovered a catch.

Unfortunately SVG exports of my crops are producing the dreaded antialiasing 'cracks' between objects that others have complained of when importing Illustrator's exports to SVG.

Is the Pathfinders > Crop command forcing a reversion of the expanded trace to Abutting paths? This would be undoing a setting I have in the Trace to produce only Overlapping paths.

For newcomers like me to Illustrator, I learned the fix for cracked SVGs is to increase the Decimal value as shown below in the File > Export Selection menu.

[federico platon]

Pathfinder>Intersect keeps common areas common to all selected objects, when two or more objects have parts unshared or not connected you will get that warning or error.

[federico platon]

Pathfinder>Crop is the straight answer. Trace the image* and expand, no need to ungroup.

*Abutting Method and create lines I think provides the best outcome.

[Monika Gause]

Those are not anti-aliasing issues. SVG reduces the precision. You need to enter a higher "decimals" setting in the options.