Hover to preview a JPEG block boundary. Drag toward the free-edge corner to refine the far corner by pixels; on an unrotated image, that is lower right. Drag inside to move or use a handle to resize. Arrow keys move a focused crop by JPEG blocks. A focused handle moves a constrained edge by blocks or a free edge by pixels; Shift moves 10 steps. Escape cancels a drag. Use Draw new to replace the selection. Zoom changes only the preview; use scrollbars to pan, or Fit to see the whole image.