pointer to valid TGA structure
pointer that will hold the data (must be large enough)
the first scanline to be read (starts with 0)
total number of scanlines to read (starting at sln)
currently only TGA_RGB or TGA_BGR possible (TGAData)
Returns number of scanlines actually read ( = n on success). This function transparently decodes any RLE data. So the returned data from this functions is always decoded. Use TGAReadImage() instead.