When the PDF image format was first made available for DPS articles, the format was limited. Most importantly, interactive overlays were not supported in PDF-based articles, so most designers stuck with the JPG/PNG image format unless they wanted users to be able to pinch & zoom on a page.
With the v18 release of the tools, that changed. Now, all interactive overlays in PDF articles work just as well as they do in JPG/PNG articles.
With the new retina display iPad, using the PDF format has now become the recommended choice for image format. PDF articles are smaller than JPG/PNG articles, and vector content is maintained, resulting in improved scaling. However, there are still some differences between the PDF and JPG/PNG image formats that you should be aware of.
UPDATE: With the v23 release, it’s now possible to create a single 1024×768 PDF folio that looks great and performs well on both the older 1024×768 models and the new 2048×1536 model. There are three main improvements: (1) background images are now output at 108 ppi instead of 72, (2) you can use a vector format for slideshows and scrollable frames to avoid text pixelation, and (3) you can include both SD and HD assets in the folio for certain overlays. I made a few edits to this blog entry, but you can learn more details by reading Creating multi-rendition articles for iOS devices.
The new iPad (Generation 3) is out. The new model has twice the resolution of the previous model. What do 1024×768 folios look like on the new device? And what’s the best approach to creating folios to account for the different devices? And when will the new device be fully supported?
When the new iPad finally arrived on my doorstep, I dropped everything to start testing it. The scaled 1024×768 JPG/PNG content looks reasonably good on the 2048×1536 device. Images look great, and nearly all overlays perform well (and don’t look pixelated when scaled up). Text is noticeably fuzzy in many areas, especially body text and light text against a color background. The performance is excellent, despite the fact that the viewer has to do some extra scaling. The new processor more than compensates for additional scaling calculations.
If you’re in a hurry, here’s the executive summary.
- Use PDF image format instead of JPG/PNG. PDF results in smaller article size and maintains vectors. To avoid rasterizing text in slideshows and scrollable frames, you can choose Vector in the Overlays panel if the viewer and folio are v23 or later.
- For single-issue viewers, you cannot create renditions. We recommend creating a single 1024×768 v23 or later folio with PDF image format for articles. This approach works for all iPad devices. For details, see Creating multi-rendition articles for iOS devices.
- For multi-issue viewers, you have a number of choices. The easiest rendition approach is to create 1024×768 source documents and use these as the basis for both the 1024×768 folio and the 2048×1536 folio. You might want to show/hide layers for certain overlays such as videos and pan & zoom images.