Keynote (& other apps) need an option to turn off antialiasing. Workaround?

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Keynote (& other apps) need an option to turn off antialiasing. Workaround?

I have started using Keynote for scientific presentations, and I generally like it better than PowerPoint. However, I am trying to create slides that show data from a PDF file, and the built-in anti-aliasing corrupts the data. My figures consist of a coarse grid of shaded pixels with labels and vector graphics overplotted. When I drag and resize the figure within a slide, it looks like it should (because Keynote is not trying to apply anti-aliasing during this manipulation). Once I release the mouse button, the figure becomes seriously degraded (due to the anti-aliasing). I see no option for turning off the anti-aliasing, and when I Google this problem I find a lot of folks who have similar frustrations (with Keynote and other Apple apps that automatically apply anti-aliasing). Some of the pages on the Apple Developer's site actually claim that "Anti-aliased objects are more accurately represented" but that is not true - smoothing of data degrades the information. The figure looks equally bad in Preview, but looks fine in Acrobat.

Does anyone know how to turn off anti-aliasing in Keynote? If not, perhaps Apple can add this option in a future patch or release?

Mac OS X (10.4.8)

Posted on Oct 24, 2006 6:53 PM

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Answer 1

Brian Peat

Level 6

18,216 points

Oct 24, 2006 7:47 PM in response to tmbrown

I doubt you can turn it off, but you might want to just figure out what size your images should be and make them into PNG or TIF images, which won't get antialiased-but also don't resize up very well (which is why you'd make them at their target size).

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Answer 2

Tulse

Level 5

5,812 points

Oct 24, 2006 9:04 PM in response to Brian Peat

Brian, are you sure that PNG and TIFF images don't get anti-aliased? When I try them in KN3, they sure seem to fuzz out at larger sizes, just like other formats.

As far as I can tell, anti-aliasing is most noticeable with re-sized images, so one solution would be to size the image as you want in some other application and then use that image in Keynote. (You could even resize by using the zoom in Preview, then taking a screenshot of the resized image.)

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Answer 3

Kyn Drake

Level 7

21,597 points

Oct 25, 2006 12:09 AM in response to Tulse

I think that's what he's saying, figure out what size your image should be, make it into a PNG and don't resize it.

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Answer 4

tmbrown Author

Level 1

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Oct 25, 2006 4:53 AM in response to Kyn Drake

Thanks for all of your replies. Even if I drag and drop a PDF figure into Keynote and do not resize it at all, Keynote is smoothing (anti-aliasing) the images embedded in the PDF figure. I.e., this is not because I'm changing the size of the figure in Keynote.

If you open one of the figures in Acrobat, you see an 8x6 inch plot of vector graphics that points to various parts of a 40x200 pixel image embedded in the plot. That embedded image takes up the full 8x6 inches, with no smoothing of these pixels. This is because documents like EPS and PDF can specify page size independently of the number of pixels (e.g., you can have a PDF that shows a tiny 10x10 pixel image at 100x100 inches if you like). In Keynote, the vector graphics and fonts look fine, but the embedded image is smoothed and degraded. When I try to resize the PDF figure on the slide, the anti-aliasing is temporarily turned off, and the figure looks as it should, but after I release the mouse button (even if I have not actually changed the size), Keynote resumes the anti-aliasing and the figure looks degraded again. There should be a way to tell turn off anti-aliasing all of the time, not just when I'm resizing the figure.

My work-around is to recreate all of these PDF figures, where I resample the embedded image onto a much finer grid of pixels, but with the result still displayed to take up the same dimensions in the PDF. Then, when Keynote applies its anti-aliasing, it is not as noticeable. But I have to recreate all of these figures at the source, and I have to make the files (both the PDFs and the final Keynote presentation) much larger. I should not have to do this to "fool" Keynote into doing the right thing.

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Answer 5

Kyn Drake

Level 7

21,597 points

Oct 25, 2006 11:20 AM in response to tmbrown

Could you explain the "embedded" graphic? Or maybe create one that I could download? I would imagine that, since Preview has a problem with it, that this is probably a "feature" of PDF that might not be a part of the public spec to which Apple applies (and is without royalty payments). I'd like to see how poorly it's getting degraded, though.

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Answer 6

Tulse

Level 5

5,812 points

Oct 25, 2006 11:41 AM in response to Kyn Drake

PDFs can have bitmap images embedded in them (and as far as I know this is a bog-standard aspect of the spec). When such PDFs are opened by Preview or Keynote, while the vector elements of the PDF are rendered correctly, the bitmapped images are "smoothed". This doesn't appear to be a bug with Preview, but a "feature", as it works the same way on purely bitmapped file formats.

In the past I've always found this behaviour quite nice, as it tends to make resized images in Keynote look better. But now that tmbrown has cast as critical light on it, it does seem supremely unfortunate that this "feature" can't be turned off on an image-by-image basis. (I presume, on the basis of the bottom of this page, that this is a Quartz effect, so I would think it would be in principle possible to turn it off and on as required.)

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Answer 7

tmbrown Author

Level 1

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Oct 25, 2006 1:58 PM in response to Kyn Drake

Could you explain the "embedded" graphic? Or maybe
create one that I could download? I would imagine
that, since Preview has a problem with it, that this
is probably a "feature" of PDF that might not be a
part of the public spec to which Apple applies (and
is without royalty payments). I'd like to see how
poorly it's getting degraded, though.

Sure. I put an example at http://www.stsci.edu/~tbrown/demo.pdf

Open it in Acrobat, and the two panels will look the same (other than the labels).

Open it in Preview, and the left-hand panel looks ok (it's smoothed, but I embedded an image that has replicated each original pixel into a 4x4 set of identical pixels, so the smoothing doesn't affect things much). In contrast, the right-hand panel in Preview looks seriously degraded.

Now make a blank Keynote presentation with a black background, and drop the PDF in there. The right-hand side looks smoothed. Click and drag a corner (to resize it), and you will see the right-hand side looking fine until you release the mouse button. You can also see that the left-hand side is suffering a little, too, but it's not as bad. I could oversample 10x10 instead of 4x4 and it would be very hard to see.

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Answer 8

Kyn Drake

Level 7

21,597 points

Oct 26, 2006 12:35 PM in response to tmbrown

Thanks for the description and the example, guys. I would also imagine that if the pixels could be output as vectors instead of bitmaps, whatever it is in OSX wouldn't feel it needs to blur it so hard.

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Answer 9

tmbrown Author

Level 1

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Oct 26, 2006 12:55 PM in response to Kyn Drake

Thanks for the description and the example, guys. I
would also imagine that if the pixels could be output
as vectors instead of bitmaps, whatever it is in OSX
wouldn't feel it needs to blur it so hard.

No problem, and thanks for the response. There are certainly various work-arounds (resampling the image up front, specifying vectors instead of bitmaps, etc.). But ideally Keynote should have anti-aliasing as a selectable option so that people don't have to go back to the drawing board on a pile of figures. For the figures that are most screwed up in this presentation, I went back to the source and redid them all (since they were in my control), but that's a hassle, and sometimes people are working with figures from a variety of sources where they are not recreated easily.

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Answer 10

La.Hoz

Level 1

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Dec 4, 2006 7:58 AM in response to tmbrown

Hi,
An unsatisfying workaround is to export your Keynote document to PDF. The new PDF document will have all your images in their original form, i.e., non-anti-aliased. You may loose special effects, etc. from the Keynote document.

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Answer 11

Tulse

Level 5

5,812 points

Dec 4, 2006 8:32 AM in response to La.Hoz

Welcome to the forums, La.Hoz.

That's an interesting find you've made -- as far as I can determine, PDF is the only export format that actually preserves the original graphic, instead of substituting the Keynote anti-aliased version. I have to think that was probably an oversight on the part of the developers, rather than an intentional "feature", but as you point out it does mean you can get the real image if you want.

There really should be a checkbox in the Adjust Image panel that says "Turn off anti-aliasing".

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Answer 12

tmbrown Author

Level 1

0 points

Dec 4, 2006 10:18 AM in response to La.Hoz

Hi,
An unsatisfying workaround is to export your Keynote
document to PDF. The new PDF document will have all
your images in their original form, i.e.,
non-anti-aliased. You may loose special effects, etc.
from the Keynote document.

Huh - that's interesting. I tried it (using the demo.pdf example I gave above) and you're correct. The exported PDF (if viewed in 3rd party software like Acrobat) does not have the anti-aliasing. Of course, once I open that same exported PDF in preview, the graphics are anti-aliased and thus corrupted. So, this workaround is unsatisfying in more than one way (that you need 3rd party software in addition to the exporting to PDF).

Thanks.

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