How to remove the "grainy filter" from reference paintings

Hi all! I'm DrHouse93. I'm not entirely new to modding, but I'm still at a very basic level. So I'll try to do some simple mods before getting into the serious stuff. Hope you can help me fix a problem that has been haunting me for a very long time. As the title says, I'm looking for the location in the game files of the DDS overlay applied to paintings by reference, aka "the abominable grainy filter". For anyone who doesn't know what I'm talking about, here's a pic:






If you look closely at the preview in the bottom right corner, you can see the unaltered original photo. Basically, when a Sim paints by reference, the game makes the player take a photo of what he wants to be painted and then applies an horrible grainy effect to the photo to make it look painted. Since I hate that effect, and also think a 5-years-old child can paint better than that, I was planning to modify the overlay image that causes the grainy effect and either change it or simply make it fully transparent. This way, paintings will look like photos, but without filters, especially that disgusting grainy one. I also tried with photos taken in the game by Sims. I love their quality (I'd like my paintings to have such a quality), but photos have a similar flaw: the abominable white border



So here's my question: where can I find that DDS overlay? I tried looking into the Recipes, but had no luck