Reading Bitmap Objects I

Cello's file format is broken up into a number of distinct objects. The simplest the shape works and publishes correctly. All the object types are registered through a GUID and the read calls a factory to make objects that correspond to that GUID. This makes for an easy incremental development. All the registration *except* for the shape object is commented out. It is possible to uncomment them bit by bit and to work through them.

The plan is to work through the objects, register them, add the files that are required (working through compile and link errors) and then test.

Having registered the bitmap GUID and worked through the comparatively few errors and additional files required, and a crash in the Color Palette class bitmaps read and write. Publishing yielded a blank (missing) image. This is because the file format, under some circumstances" contains a reference to the image as a hard path. The fall-back behavior at publish time for a missing image is to just omit it.

Having a hard path to an image presents some problems for testing. the work around is to have a mechanism that will change the path in a file after the file has been been read. I did this by having a simple class that has a list of files with full paths and will match a file against the list based on the file name - so

/users/scratch/nonsense.jpg

will match against

C:\Documents and Settings\All Users\Sample Pictures\nonsense.jpg"

This kind of matching is easily done with Core Foundation's CFURL. CFURLCopyLastPathComponent will get the last path component of a path i.e. nonsense.jpg and URLs can be constructed form POSIX, HFS and Windows paths.

Having added the code - it is clear there are some problems with the publishing. See below: