如何从其他PNG中复制一个PNG?

My application needs a lot of PNGs and I often mess up my code while trying to work with them. To make my life easier I made one big PNG image in Realword Paint and pasted all those small PNG images on to it. Now I have one file instead. Now all I need is to copy one PNG on to other with transparency (btw don't ask why), because I need to work with each image induvidually. I am bad programmer when it comes to working with images. I am using Delphi 7.My application needs a lot of PNGs and I often