Memory leak while converting images with FreeImage.Net

When loading the image with the nuget package, (FreeImage 3.18.0.0) it does not unload memory even if '''dib.SetNull()''' was set.

var dib = FreeImage.Load(FREE_IMAGE_FORMAT.FIF_PNG, pngFile.FullName,FREE_IMAGE_LOAD_FLAGS.DEFAULT);FreeImage.Save(FREE_IMAGE_FORMAT.FIF_JP2, dib, jpgFile.FullName, FREE_IMAGE_SAVE_FLAGS.JPEG_OPTIMIZE);dib.SetNull();