More Bitmaps - DIBS and CGImage

[build 0029] I have been working on bitmaps and bit images and the whole thing is slowly coming more into shape. The issue that I have been having with bitmaps is that fundamentally the bitmaps that are imported into Cello using Image IO as a CGImage are richer and more complex than those represented by DIBS. A CGImage has notions of byte order (big and little endian) and different data packing. Below is a classic example of the sort of an endian problems that you can get.Additionaly there are wrinkles such as GIF images and PNGs with a color table are imported as indexed 16 bit colors. One byte is an index into the color table the other is transparency. Also internally Cello wants to deal with non premultiplied alpha, where as the export needs the alpha pre multiplied.

In with all of this I have discovered that it is possible to get a direct copy of the pixel data of a CGImage - using CGImageGetDataProvider.

With all of this I have changed my approach a little. I have added a CGBitmapInfo to the OSX version of the MFC bitmap header so that I have an idea of byte order and packing. I have also written, and tested, some templated pixel accessors so I can easily access the various channel packing orders.

All of this needs to be integrated with the existing image export so there is still a fair way to go before the image side of things is wound up.