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. Drag outside the crop to replace it. Choose a ratio to lock the shape, and use Undo (Ctrl+Z) to step back. Scroll over the image to zoom toward the pointer. Use scrollbars to pan, or Fit to see the whole image. On a touch screen, one finger crops; pinch or drag with two fingers to zoom and pan. Shortly after you draw a small crop, the preview zooms toward it.