How can I compress my portfolio into something that won't load like a bad animated GIF?
November 20, 2011 8:26 PM   Subscribe

Can somebody please explain to me image compression, specifically with regard to creating smallish PDFs from Indesign files that contain large linked vector graphics?

No matter how many times I think I have a grip on compression and resolution and all of those terms, I still end up creating enormous files with no idea what is controlling what.

I am creating a portfolio in InDesign CS4 in which I have linked a lot of large files, mostly Photoshop files and a lot of very large Vector graphics (AI files). From InDesign, I will export the file as a PDF, using the High Quality preset for example. These files are huge, but are lovely when I print them. However, if I want to email a PDF to someone or create a smaller version, I have no idea how to compress these things.

If I try to optimize the PDF or export using settings as low as 72ppi, the file sizes are still huge and the vectors seem to load almost like animations. It seems the large vector drawings are the problem, but I can't seem to figure out how to "flatten" those without making the normal text in the file look terrible. The best option I have found so far is to just export the whole PDF as images, and then recombine into a new PDF but even these are pretty big and the regular text (captions, titles, etc) look a little gritty.

I guess I am not sure where in this process I should have been scaling down the large vector images or even the original PSD files (I was under the impression that these originals should stay uncompressed). Should I have scaled down the original images? Should I have changed some setting in InDesign? Is there a secret setting in Acrobat for vector images only that I can't find?

Please help me figure out what is controlling what, and help me avoid having to hire a courier to carry over a stack of flash drives instead of just emailing a nice, neat PDF.
posted by This_Will_Be_Good to Media & Arts (14 answers total) 5 users marked this as a favorite
The vector images are being stored as is, with Zip compression but not any less complicated, would be my guess. Are you using the "High Quality Print" PDF preset, as described here? What happens when you select "Smallest File Size"?
posted by wnissen at 9:16 PM on November 20, 2011

How many pages, and what are your definitions of "huge", "pretty big" and "emailable" file size?
posted by misterbrandt at 9:29 PM on November 20, 2011

Response by poster: I have tried both -- I thought the Smallest File Size option would be the solution. The file is much smaller, but the vectors drawings are still loading very slowly (as if they are building up like an animation). It definitely makes the file about 1/3rd the size, but I still feel like I don't have a lot of control and no direct control over the vector images it seems.
posted by This_Will_Be_Good at 9:30 PM on November 20, 2011

Response by poster: misterbrandt -- a 12 page version is about 32MB.
posted by This_Will_Be_Good at 9:32 PM on November 20, 2011

When we need to email PDFs at work, we open them in Acrobat and use the "Reduce File Size" option found under the "Document" tab in the menu bar. It does a good job of shrinking the files with them still looking decent.

The vector graphics, however, are unfortunately going to draw in like that no matter what you shrink. It's what happens when InDesign creates the PDFs; they print beautifully but they're annoying on screen. One solution would to be to create JPG versions of the PDFs you want to show off. Or to make them flat Photoshop PDFs at a smaller size, say 96 dpi. Once you create a version where the vectors are now raster images, they won't draw in like that. Anyone looking at your portfolio isn't going to print off huge copies of what you present; they want to see what you can do and a nice crisp image can do that as long as it looks clean. You can always bring the hard copy of your portfolio to any interviews and they can see the finished product there.
posted by azpenguin at 9:46 PM on November 20, 2011

I would try [on preview: what azpenguin said] exporting the vector images to a raster format at 96 or 192 dpi— ideally a lossless format like PNG— and including those in the PDF you are mailing. This loses a huge amount of information and detail, which is why (a) the file is smaller and displays faster and (b) you want to keep the originals around for printing, etc.. For portfolio purposes, perhaps you could store the full-detail vector PDFs on a website somewhere and link to them from the reduced-detail PDF that you email?

Vector images don't lose information when they get scaled down; they retain all of their detail, just smaller. Which is great, but it also means the file doesn't get smaller— it still contains the same info. If there were such a thing as lossy compression for vector images, that might do what you want, but I don't know of software that does that.
posted by hattifattener at 10:12 PM on November 20, 2011

One thing you could do, if quality is important, is to selectively convert the biggest, most detailed vector drawings to JPEG or PNG (whichever is appropriate). This would obviously involve making a whole separate version of the document, as it wouldn't be something you could do on export, so it would be a pain. I agree that bitmapped text is quite jarring, even rendered at a fairly high PPI, when compared to native font rendering, so it might be worth it. No one will notice that your pictures are only 144 PPI, but they might notice the text.

For what it's worth, "compressing" vector images is in some ways harder than raster (which itself involves Fourier transforms and lots of good math), so it's not inDesign being obtuse.
posted by wnissen at 10:43 PM on November 20, 2011

Response by poster: wnissen -- I think you may be right, there are definitely a few pages here and there that seem to be oddly larger than others. So, it make sense to target the originals for those a bit first.

In the meantime, after going through lots of menu options, I can't say I know what I am doing, but I have come up with some sort of workflow that I feel like I have a bit of control over based on what azpenguin and hattifattener said.

High Quality Vectors: From InDesign, I am exporting PDFs using the High Quality preset. I can print directly from these, and there is no obvious reduction in quality that I can see. They are large, but pretty.

Lower Quality, Still Vectors: From the High Quality PDF, I have gone through and tweaked all the various settings they give you. I have reduced all the image sizes, discarded all the objects that I don't understand, and lowered transparency settings (I don't know what that is affecting, but it seems to help). I can usually cut the file size in half going this route.

Lower Quality, Rasters: From the High Quality PDF, I have exported the pages as TIFFs. I finally found a drop down menu there next to the TIFF option that lets you set color mode and PPI (before it was randomly converting pages to various PPIs and color modes). So, each page has been rasterized to avoid the slow animation-like building up of complex vector drawings. The quality might still be decent for some printers, and I can probably reduce the file size until I get something about as small as the low quality option above. I imagine if I choose to export first as PNG or JPEG I can really reduce the file size down more, but I'm sure things will start getting choppy again.
posted by This_Will_Be_Good at 11:26 PM on November 20, 2011

Response by poster: Now that I have looked over the raster images I have exported, I am still a bit confused: If I have a PDF with all 8.5" x 11" pages, and I have exported every page as a raster at 300ppi (I used PNG), then why are all the images different file sizes? If all the images have the same dimensions and PPI, won't they all be the same size regardless of their content?
posted by This_Will_Be_Good at 12:00 AM on November 21, 2011

Raster images stored in PDFs are still compressed (losslessly, unless they're JPEGs). This doesn't change their appearance from an uncompressed raster image, but the size of a compressed file depends on the complexity of the image ("complexity" isn't quite right; it's also a matter of how well the image's content matches the way a given compression algorithm expects images to be, but thinking of it as "complexity" is not too far from the truth).
posted by hattifattener at 12:09 AM on November 21, 2011

Print your files to a PDF printer (like primopdf) to quickly create flattened / smaller pdf files.
posted by seanyboy at 2:43 AM on November 21, 2011

If all the images have the same dimensions and PPI, won't they all be the same size regardless of their content?

Because of the way compression routines work, the color/tone/detail complexity of the image affects the resulting image size.

An 8.5x11 image of a polar bear in a snowstorm is going to result in a smaller image size than an 8.5x11 image of, say, a circus parade.

Does it make any difference in the resulting PDF if you insert/paste the vector graphics directly into the InDesign document, rather than link to an external file?

Additionally, when placing raster images into any document, re-size them in Photoshop to the exact size you need them at, then place that smaller image in the InDesign file. This will make the resulting PDF much smaller and gives you greater quality control. Placing a 10meg image in the InDesign file and then scaling it there does not result in a smaller image file size. You still have a 10meg image.
posted by Thorzdad at 4:40 AM on November 21, 2011

This doesn't directly address your question, but in case it might help:

Is the only reason you want to reduce the file size is so that you can email them? Because you could use something like Dropbox to share large files with your collaborators. Sometimes, you simply cannot make files small enough to email (I certainly can't in my line of work), and have to find alternative means of sharing them.
posted by kisch mokusch at 4:55 AM on November 21, 2011

To a first approximation, image compression works by taking a bunch of pixels and turning them into vectors. Usually not the same kinds of vectors you get in an SVG file, but still: basic run-length-encoding compression turns the pixels into a series of lines of specified length. So image compression in the usual sense doesn't apply to SVGs, although you can fake it by minimizing the number of objects.

Regarding the bitmaps, there are different compression routines that are better for different kinds of image. The usual "I need these images by five minutes ago!" advice is to use PNG for images with plain backgrounds and shapes of solid color, and JPEG for images with gradients and "fuzzy bits" like what you get from a camera.
posted by LogicalDash at 5:13 AM on November 21, 2011

« Older Tell me the things you wish you had known before...   |   Easy bake cookies Newer »
This thread is closed to new comments.