Throwing out redundant bitmap information when saving as PDF

Question

I am designing something in Illustrator and I use a part of a bitmap (JPG) image. I only need it to cover a specific shape so I use a clipping mask and end up using just about 20% of said image. Now when I save as PDF, whichever way I save it, it retains the entire JPG inside the PDF (you don't see it, but it's there). How do I get rid of the 80% I don't use? I'm also fine with throwing out that 80% in the AI file, as long as I get rid of it.

PS: It's for file size purposes.
PPS: Yes, I've tried unchecking editing capabilities and checking acrobat layers.

Answer 1

You can re-rasterize the image directly in Illustrator to get rid of the unused part of the image. Take this clipped image for example:

With your clip group selected go to Object → Rasterize...

Choose your desired resolution (this will rasterize your image to that resoltuion at its current size in your document so make sure it is scaled appropriately or you rasterize at a resolution higher than you need). You can check "Create Clipping Mask" to retain the clipping mask or you can rasterize with a transparent background.

You can see that the actual image dimensions are unchanged, but the clipped areas are removed and you can rasterize to the maximum resolution you require so you should still save on file size.

Answer 2

There is no checkbox to achieve this, as AI only works with rectangular bitmaps. If file size is the issue, your best bet is to compress the JPG to something smaller if possible, or take the artwork into Photoshop, as this lets you truly remove parts of a masked image and then save your PDF from PS.

Answer 3

The simplest solution is to save a version of the image that is cropped down to just the portion that you need. Then place that into your artwork before saving the PDF. That way you won't be saving any extra data because the unused portion of the image is not there.