With irfan view we are going to make a sprite's background transparent. (Without the white box around it).
Once you download it, open a sprite in paint and dump a color on the white around the sprite. Where ever the color is will be transparent. I usually use bright green but you can use whatever color you wish. (Just try to avoid the color white and any other color your sprite contains.)
Now, save (as BMP) and open it up in irfan view.
Next, go to File>save (or press the S key) Select the file type: .PNG and a popup window will come up. This is what you should have on your screen.
Click the save button and a select transparent color window will pop up.
Select the color you want to be transparent. If you don't want any color to be transparent pres the Esc button. Note that the image will not look transparent while open in irfan view.
If your image has some of the color transparent and some not this means there is more then one color (but they are so much of the same shade it is hard to tell there are 2 different colors.) This usually happens when you try to use an image that is/was a file type that causes discoloration (.jpg or .gif) To fix this you will have to use paint and change it all to one color. (the way I do it is to dump 1 color a different se I can see both colors and make them both the same color.)
