Combine different bands of TIFF file

Hi all,

My project is dealing with High Resolution satellite image. And the company that provide us with the satelite image has delivered the image in 4 bands: red, blue, green and panchromatic separately in TIFF6 format they are using 16 bits per pixel.

Now my problem is I have to combine the 3 bands red, green, and blue together to get the resulting image. I have tried to code myself but always got problem bcoz the file size is to big arround 25MB and I always got a blank white image.

Does anyone knows is there such a free library or program to solve my problem? Thanks in advance.