Image quality after crop

Hi guys i've implementet image cropping as per:
http://world.episerver.com/blogs/Mark-van-Dijk/Dates/2014/11/extending-the-imagedescriptor-attribute/

But clients are saying that images are loosing quality after resize and crop. I found that this part of the code is doing croping 

ImageService.RenderImage(numArray, 
                imgOperations, 
                mimeType, 1f, 50);

and i tried changing 50 to 100 (parameter that controls image quality) but no luck.

Also when client is croping images in image editor trough edit window they say quality is ok but they whant that proces to be automatic.

Any ideas how to fix this ?