So I had a 4800 x 7860 wallpaper and wanted to it look blacker or have more contrast in it. So I used gallery to apply a filter on it and there was no problem with filter it made image more contrasty
BUT it downscaled the image to 2804 x 4487.
So does it means there is a resolution limit in gallery app for applying filters.
If not please fix this issue I didn't notice quality difference in this one because it had more pixels than phone could display. But this issue is only with ultra high res images.