To create a texture pack you first have to install a graphics program that supports alpha channel (i.e. transparency). I think the one which is built into Windows 7 (Paint) does not support it – but I may be wrong.
If you’re on Windows, I think your best option is Paint.NET – a cute, free little program that is very good. Incidentally, this is what Notch used to create original Minecraft graphics, so you can’t really go wrong here.
If you want something more powerful, get GIMP. But if you haven’t done much graphics before it will probably take you some weeks to grok :-)
- Texture is divided into 16 by 16 slots
- File format must be png, and it must be 32 bits per pixel (otherwise you lose alpha channel).
- Each slot contains image for a certain type of block. Sometimes multiple slots can be used for a single block if it looks different on some sides (e.g. chest or crafting table)
- Alpha channel is used to create transparent blocks, such as glass, doors, leaves.
- Alpha must be either 0 or 255, that is fully transparent or fully opaque. Partial transparency is not supported by the game engine
- You can resize the texture to get better resolution, but it must always be divisible into equal blocks, and there must be 16 by 16 of them
- If a slot does not have any transparent pixels, making it transparent will cause glitches. Only certain blocks support transparency, not all of them. For example you cannot make dirt or granite transparent.
- If there is something wrong with your texture pack, the game will revert to the default one.