Here is a How-to guide to DIY Chinese Visa Photo. The requirement of it is 33mm x 48mm, a little bit smaller than 2 inches. Here is a sample picture from official China embass website. So just take a picture by yourself and use any photo editing tool you like.
You take the pictures, and want to print it on your color printer or through Costco photo lab. But you don’t know the max size you can print. Here is a handy printing guide for it. 5 MP = 2592 x 1944 pixels High Quality: 10 x 13 inches Acceptable