One of the benefits of QuickTime is that it was designed to be a very open-ended developer technology. So when you ask if QuickTime is PICT specific, the answer is a strong NO. However, any given compressor/decompressor (CoDec) component will usually be specific to a specific data format such as PICT, TIFF, TARGA, and so on. You could write a TIFF or TARGA CoDec, provided you have the expertise to do so.