[DO NOT MERGE]fix simplification of drawImage

@egeerardyn, please have a look at this. This is a partial fix for the changes you recently applied in order to simplify the drawImage function. I am still having issues workin with git. The commit https://github.com/PeterPablo/matlab2tikz/commit/25ba4c08a000d03b02895e71f2c82ab25ad131b2 is the important one. I was working on the mandrilla testcase when I encountered the issues. I tried to export the image to tikz. As you see in ACID.m I reduced the image to a 10x10 matrix. There remains a bug in the code below `% The following section takes pretty long to execute, although in`.
I need to go now. Hope this helps.