In Photoshop, you can select the background and then delete it and then you need to save the file as a png. Then... TA-DA! You have your transparent background. ^^ Also, you can you [link] and just upload your picture as a jpeg and one of the vibrant colors below and then it takes that color away (if you know what I mean) and then you get a transparent background that way, too! And... I never used SAI before.