I have 2 types of thumbnails. I use Imagemagick.
Video Poster Thumbnail called "b" images.
The width and height is 278x170 for small thumbnails but I cropped them 208x128 to get rid off watermarks and I do.
I have my php files first and rest
I pointed the place where "b" images have been but I don't know how to edit these codes to crop that "b"images same as small thumbnails to crop watermarks by not decreasing the quality of picture of "b".