8X8 LED Matrix multiplexing code help

Hello people! I am currently enrolled in a project in which i use an 8x8 RGB LED Matrix with common annode and i am wondering if any of you have or know of an app or program to design sprites or art in the 8X8 way and that it translates it into a piece of code. For example, this page is indeed what i am looking for but for a rgb matrix. Also i currently have only 7 seven colors because i have it hooked with four 74HC595 so the simplerthe program the better. Ah, and if it can be accessed online or it is an app (iphone app) it would be best. Just to give some ideas i am planning on controlling the matrix using Wifi with an ESP8266 so i would love to make the sprites on the go and be able to upload them into the arduino.

If there is anything else that i must specify, please let me know. THANKS!