Document image inclusion in espass format

[eternaltyro]

I downloaded the example passes from espass.it and I noticed that the files named strip.png and footer.png automatically find their places in the pass display when they are included in the container. As far as I can see, this is undocumented in the espass spec. I can help with documentation for this.

Seems to be hardcoded here: https://github.com/ligi/PassAndroid/blob/2eae832bc0ccd6f90b79a0dde9af6d0cfb2f0f4c/android/src/main/java/org/ligi/passandroid/ui/UnzipPassController.kt

• 1. Types of images that can be included (PNG, SVG?)
• 2. Name based positioning (strip.png, icon.png, logo.png and footer.png)
• 3. Dimensions of images in pixels and
• 4. Max size in kilobytes of each images.

Most of this depends on the passbook application rendering the images. So esPass spec might be agnostic of all of these. I'm not sure though.

Raised the same issue in PassAndroid project too: ligi/PassAndroid#173

[eternaltyro]

Seems similar to this: https://developer.apple.com/library/content/documentation/UserExperience/Reference/PassKit_Bundle/Chapters/PackageStructure.html