Dean (and all) -- I have a few comments and pointers for you.
1. JPEG Quality within SWF Export
First and foremost, unfortunately there is a bug in the JPEG Quality setting of the InDesign CS4 SWF Export dialog. The bug is that no matter what value you choose from the pop-up menu (Minimum, Low, Medium, High, Maximum), they will all end up as Medium quality. The bad news is that this bug was not discovered (internally) or reported (by pre-release and CS4 customers) before we shipped CS4 (6.0.0), or the 6.0.1 dot release. The good news is that it will be fixed in the next dot release (6.0.2). I can't provide a specific date for the next dot release yet.
2. JPEG vs Lossless (Do Nothing)
This is a case of poor wording in the user interface. The Lossless choice listed in the Image Compression pop-up menu has nothing to do with JPEG. If you choose Lossless, the bitmap images in the SWF will be exported as PNG files. JPEG is a file format that uses Lossy compression, whereas PNG files use Lossless compression. PNGs usually look better than any JPEG exported below Maximum Quality, but have a much higher file size than JPEGs. For the next version of InDesign, we plan on renaming these two options to make them more understandable. Instead of "JPEG" and "Lossless (Do Nothing)", they will be changed to "JPEG (Lossy)" and "PNG (Lossless)". To make it even better, ideally when you choose Lossless, the JPEG Quality option would grey out to reinforce that it has nothing to do with the Lossless option. For now, I hope my explanation here helps.
3. Resolution of Exported Images in SWFs
Yes, if the effective resolution of an image placed in InDesign is higher than 72dpi, then SWF and XFL Export downsamples them to 72dpi. This downsampling happens BEFORE the image compression choice (JPEG or PNG) kicks in. This was intended to be a helpful feature. Our thinking was that if you wanted to export a digital version of a document whose primary purpose was to be a print document, this would save you from having to manually resample every placed image in Photoshop and relink them in InDesign. In that context, it is a helpful convenience.
4. "Zoomable" Digital Documents
However, for the use case you are going after, meaning you want a digital version that can be zoomed in on by the end-user, this downsampling to 72dpi doesn't help you. You want your bitmaps to be at least twice the screen resolution so that when you zoom in on them in the Flash Player, you see the additional pixels at that zoom ratio instead of a bigger version of a low resolution image. Based on feedback from threads like this, we have captured that it would be helpful to allow the user to specify what resolution they'd like the bitmaps within the export SWF to be and we hope to add that feature to a future version of InDesign.
That said, adding this would still not get you what you want. You want the user to be able to zoom in and then pan the digital document around. Unless you build that functionality into your actual SWF, just having higher resolution images in your SWFs isn't going to satisfy what you are after. When you right-click on any SWF file in a web browser, you'll get a context menu that gives you the option to Zoom In. Once you do that though, the Flash Player does not change your cursor to a Hand tool to let you pan the SWF around, nor do you get scroll bars. Maybe exporting a "pannable" SWF is something we could add to a future version of InDesign, but for now, that is why we included export to Flash CS4 Professional in addition to direct SWF Export in InDesign CS4 so you can add that functionality to your digital documents there.
In many of the examples I've seen where you can zoom in on a digital magazine, they are actually using a hybrid approach. Meaning, there is a 144dpi PDF as a base layer, and then the interactive and animated content are SWF files overlaid on top of the PDF content layer. These digital magazines are typically published in partnership with one of the vendors who focus on converting the very same PDF that was used to output the print version of a magazine. They use that PDF as their starting point, and then layer the interactive content on top. Your last post in this thread points out that you've cobbled together a similar approach to what you are trying to achieve.
4. Tip: JPEG Pass-Through
Here is an undocumented feature in the InDesign CS4 SWF and XFL Export commands. I call it JPEG Pass-Through. What it means is that if you place a 72dpi JPEG into InDesign at the dimensions you intend to use it in your SWF/XFL file, the JPEG gets "passed through" exactly as it came into InDesign. Meaning, it will not be resampled and it will not be recompressed. If you scale the JPEG in InDesign however, then the downsampling and compression options will kick-in at export time.
5. Related Tip: Designing with Pixels in InDesign
No, you cannot choose Pixels as a measurement system in InDesign (any version through CS4). However, you can use Points as your measurement system as a workaround. By default, 1 point equals 1 pixel in InDesign because a point is 1/72nd of an inch. So if you draw a rectangle that is 400 points by 300 points in InDesign, when you export at 100% to SWF or XFL, you'll end up with a 400 px by 300 px rectangle. So... if you intend to use InDesign to create a digital document from the start, instead of "converting" a print document, use Pixels as your measurement system in Photoshop, and set the resolution of the images you'll use to 72dpi. Save them as JPEGs, and control the image quality of the JPEG as part of the JPEG or Save for Web options out of Photoshop (or Fireworks). When you place them into ID, they will come in at "actual size" if you just click on the page with the loaded Place Gun. If you don't change their scale, they will go out to SWF exactly like they came in.
I hope this information is helpful to you. This feature set in CS4 was our first attempt at having InDesign be a layout tool for interactive content in addition to being the best print layout tool on the planet. (OK, as the product manager, I'm obviously biased on that last part. :)
We believe it provides useful functionality for making interactive presentations and interactive documents with simple buttons, page transitions and hyperlinks via SWF Export. If you need to go beyond what you can create through direct SWF Export, you can hand-off to Flash CS4 Professional and continue working on the project there via the XFL Export option. InDesign CS4 was not intended to be the only thing you'd need to replicate all the functionality you see in solutions such as Zinio, Texterity, Ceros, nxtbook, etc.
For now, I apologize for the unfortunate bug mentioned earlier. Know that we are working diligently to resolve that. Until then, the "JPEG Pass Through" tip can get you better results.
Cheers,
Michael Ninness
InDesign Senior Product Manager
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