There are strange lines and shapes in my image

That is the Moire effect (google it).

Determine if it is in the image or just in the monitor. Zoom in and out. If the identical moire lines appear no matter how much you zoom, then its in the image.

If in the Image:
Get a new grid with a slightly different Lines Per Inch.

If in the Monitor:

  • Pick a slightly different resolution in the PC settings for the video adapter. OR
  • Get a new monitor with a slightly different resolution.