Background Image for Android Activity

I would like to create an image, which I want to use f开发者_StackOverflow中文版or the background of an Activity. There are two questions I would like to ask.

1) What type of image should I create e.g bitmap, nine-path, etc?

2) What software should I use to create the image?

Your help would be most appreciated

1. .PNG format, 9-patch, it allows transparent regions where are needed. (If I may say)
2. Adobe Illustrator (this is not advertisement) or similar.

1. What type of image should I create e.g bitmap, nine-path, etc?

You do no need to create a nine-patch image if you are going to use this image as a background for your activity. Because nine-patch are stretchable image which i think you won't need for background as any normal image will work great for you but you should check the resolution of the image before using it as it could be distorted if its resolution is less than device's resolution.

2.What software should I use to create the image?

You should use photoshop as its the best option available at the moment and has some great features which lacks in other software of similar type.