Converting Images of any format to ASCII characters is normally a tedious job because you need to download ASCII conversion tools/softwares to your computer which after installing you can start converting. But when you are looking for a instant tool then check out Make Ascii tool which offers you with 2 options where you can upload images directly from your computer or a image URL and then convert the images directly to ASCII characters which can be directly saved or as a image.
Here is a sample image i have converted
