Use ushort in TGA header, not short
Rename ImageException to ImageIOException
Make PNG_Encoder private
Start TGA encoder: writes the header
Better attribute checking for TGA decoder
Make TGA encoder write image data (no RLE, no footer)
Delete some comments
Write footer to TGA files
Add RLE compressor for TGA encoder
Refactor RLE compression into a function (line-wise)
Delete dead line (TGA)