Copy and Paste an Image from a PDF, resolution problems

Discussion in 'Mac Basics and Help' started by fliptomato, Jul 24, 2008.

  1. fliptomato Guest

    #1
    Greetings -- I'm having trouble copying-and-pasting an image from a PDF. When I use Preview or Skim, I can select a region of a PDF and click "copy" and then paste that image into another program -- HOWEVER, the resolution of the pasted image seems to be fixed and not very good.

    In Windows using Acrobat Reader, I would just zoom in and copy a region to get a higher-resolution copied image. However, no matter how I zoom in OS X I don't get higher-res copies.

    I found a limited alternative, which is to use Previews 'grab' to select a region of the screen and copy as a tiff. This is essentially a 'print-screen' so that the resolution is as good as the current view. HOWEVER, this is rather limited and annoying because one needs to have the entire image able to fit on screen and because one has grab, then open the resulting file on the desktop, and THEN copy and paste from that new file.

    Does anyone have tips on how to grab high res images off a pdf?

    Thanks,
    Flip
     
  2. NAG macrumors 68030

    NAG

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    #2
    Depends on the PDF. Some PDFs have drm to prevent copying. Some are just low resolution.
     
  3. fliptomato thread starter Guest

    #3
    I'm pretty sure these PDFs don't have DRM and are high res. For example, I should be able to copy text as an image at arbitrarily high resolution. (Shouldn't I?)
     
  4. NAG macrumors 68030

    NAG

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    #4
    Not necessarily. PDFs can be about any resolution under the sun. And just because it looks okay on your computer screen doesn't mean it is high resolution (your screen is only at 72 dpi).

    Without more specifics as to what you're doing I can't really help.
     
  5. fliptomato thread starter Guest

    #5
    But surely if the PDF contained a vector image, it should be resolution-independent, shouldn't it?

    Ok, so let's work with a concrete example. Consider this PDF:
    http://arxiv.org/pdf/0807.3596

    Attached are two 'copies' of equation 2 of this paper:
    • eqn2.jpg is the result of 'copy and paste' in the usual way (at any zoom)
    • grabeqn2.jpg is the result of Preview's 'grab' taken with the image zoomed in. (This outputs an image file, which one can THEN copy from to paste at the higher resolution.)

    The resolutions are clearly different, right?

    If one were to open this file using Adobe Acrobat in Windows, one could directly copy-and-paste at the resolution of the screen. (One would also be able to scroll while making a selection, so that one could select an area larger than the screen at the resolution of the current screen.) I don't know how to do this in OS X.

    Thanks,
    Flip
     

    Attached Files:

  6. NAG macrumors 68030

    NAG

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    #6
    You sure it is vector and not raster? Zoom in a lot and see if you see pixels. If so, it isn't vector.
     
  7. fliptomato thread starter Guest

    #7
    Hello NAG, I was pretty sure (but could be wrong) that text is rather resolution-independent in PDFs. Did you look at the images I posted? Those were not resized or otherwise modified -- they're at the native resolution of the "copy and paste" versus the "grab" methods. As one zooms in the text does not become grainy.

    But just to be sure I did another experiment and created a vector image using Inkscape and saving as PDF (via Cairo). The image contains text, but the text was converted to a vector path.

    I'm including the original pdf (drawing.pdf) containing the vector image. copy.jpg is the resulting image that one gets using copy and paste into an image editor -- this is independent of how much one zooms in. grab.jpg is the resulting image one gets from using 'grab', which DOES provide higher resolution copies if one zooms in before grabbing.

    Is there any way to get the higher resolution using copy-and-paste rather than having to go through the (somewhat limited) intermediary of grab?

    I've given you a link to a pdf in a previous post on this thread and am now also including drawing.pdf in this post. Hopefully this will help our communication.
     

    Attached Files:

  8. heehee macrumors 68020

    heehee

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    #8
    You can just zoom in in preview and use File >Grab > Selection and select the area.
     

    Attached Files:

  9. fliptomato thread starter Guest

    #9
    Hi heehee, Indeed that's one way to do it, but I was hoping there would be an alternative for two reasons:

    1. Grab appears to be limited by the size of the window. I.e. I can't scroll when I'm grabbing an image, so the image better fit into the window. If I wanted to grab a very high resolution of an image larger than my screen, then there wouldn't be a good way to do this.

    2. Grab creates extra files on my desktop that I then have to clean up. (Instead of the convenience of copy-and-paste.)

    Thanks,
    Flip
     
  10. IJ Reilly macrumors P6

    IJ Reilly

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    #10
    The cropping thing in Preview doesn't work very well, if the purpose to export the result as a different format. If the PDF includes bitmapped images the resolution of the copy will be less than the original. The work-around is to crop the PDF then print the result to a new PDF. This new PDF can then be converted to an another image (e.g., JPEG) format at the original resolution.
     
  11. mkrishnan Moderator emeritus

    mkrishnan

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    #11
    Erm... *points above* In any event, this solution will always produce a bitmap that's limited to screen resolution. Even if you zoom in so that that little image segment occupies the entire screen, the DPI of the image as used in the other document will probably be low for printing.

    I've had this problem also... I typically have used the workaround you describe. Depending on what you're embedding the image into, another possibility sometimes is to crop the PDF down to the part you want and re-save it under a new name, and then insert the PDF as an image into the document (using the insert image type of command in the app). Some apps support that.
     
  12. heehee macrumors 68020

    heehee

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    #12
    I missed that part. :p

    OP: How do you even copy and paste (a picture not text) using windows in Acrobat?

    If you have illustrator, it would solve this problem.
     
  13. fliptomato thread starter Guest

    #13
    Ah -- it took me a while to understand what IJ meant by this, but now I see, and it works perfectly.

    For example, I use Skim to view pdfs. To make a `proper' copy and paste (at the original resolution), make a selection and go to Edit > Copy (as usual). Then instead of pasting into a graphics program, first go to Skim > File > New From Clipboard. This will create a pdf with the selection at its native resolution. This means that vector components (like letters, I think) stay vector and can apparently be zoomed in to one's heart's content without any loss in resolution. OS X is very pdf-friendly, so one can usually import the resulting pdf into whatever application you needed the image for.

    For me I just needed to get native resolution pdfs at the end of the day, so this ends up skipping the middleman of a graphics program. For basic editing I've found that Inkscape works relatively well and preserves the vector nature of the file where appropriate.
     
  14. rachelwells macrumors newbie

    Joined:
    Jun 18, 2009
    #14
    i feel your pain

    Hi,
    I haven't read this whole discussion so hopefully my advice is not already here. I have the same problem copying high resolution images from pdfs to powerpoint presentations. I have tried using Abobe Reader and the image copying system is terrible, it's hard to even select an image that has writing in it. I did not have this problem when I was using dirty Windows.

    Here's how I get around the problem. Zoom the image until you have the desired size. Then press 'command, shift, 3' to image capture the screen. The image saves to the desktop as 'picture 1.' Then open that new file, select, press 'command and c' and then paste into the powerpoint presentation. This gives a really nice resolution.
     
  15. hodgeheg macrumors regular

    Joined:
    Dec 7, 2008
    #15
    I think I can solve your problem (but you'll need to test)

    By the way, those equations are vector in the PDF you sent.

    You want Inkscape.

    It is a vector graphics application that is capable of opening and editing (non-DRMed) PDFs on a page-by-page basis. Vector images usually remain editable and text remains editable text. If you ungroup objects you can do seriously complicated editing (much more so than even Acrobat 9 Pro Extended can do - which I have also - in the absence of Illustrator or Photoshop).

    Inkscape can export to bitmapped file formats at arbitrary resolutions.

    It's a little bit of a workaround, but it will do what you need, afaict. It's free anyway and opensource and there's an Inkscape.app mac binary version. It's not the most mac-like app because it's a crossplatform thing ported, and uses X11 (which you'll have installed by default if you're in Leopard, but may need to install if you're in an earlier version of OS X) but it's surprisingly capable. It can also export PDFs that are still editable and retain any vector elements and text as resolution independent. It's limited to single pages I believe, but you can easily merge PDFs into a single one using Preview.app.
     
  16. MacBoobsPro macrumors 603

    MacBoobsPro

    Joined:
    Jan 10, 2006
    #16
    PDFs were made so they couldn't be edited. So when you send a file to the printers they don't mess everything thing up and then say thats how we received it.

    Then some bright spark decided it would be funny to add editing tools to our PDF apps and all hell broke lose with regards to artwork being sent as PDFs from clients expecting you to redesign the entire thing from a low res PDF. Then once you have wrestle with that and sent the file to the printers it comes back wrong because the printer has played with it too.

    PDFs can be any resolution, they can have embedded fonts, they can have fonts converted to paths (vector or raster).

    Unless the PDF was created at a high resolution and many are not as they never end up needing to be printed professionally, then what you will most likely have is a low res PDF optimized for the web. If the fonts are embedded then you can just copy and paste the text out of the PDF. If the fonts have been rasterized or not embedded then they are effectively an image and you cant do much with it (if anything). If the PDF contains images and its low res then you are pretty much stuck with low res imagery no matter what you do to it.

    Think of a PDF as a container. If you put low res stuff in, you only get low res stuff out. Getting stuff out to begin with is a pain in the arse. The best way is to use illustrator but that still doesn't give you total control as text gets broken up into loads of different text boxes and you get the occasional crappy conversion. If you can I would suggest using Illustrator, but remember the rule: Crap in, crap out!
     

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