Show a preview of the start or end frame while transforming a strip's start/end handles.
全部刷新
To force Blender to re-read in files, and to force a re-render of the 3D Viewport,
click the Refresh Sequencer button.
Blender will update and synchronize all cached images and compute the current frame.
Certain operations, like moving an object in the 3D Viewport, may not force the Sequencer
to call for a refresh of the rendered image (since the movement may not affect the rendered image).
If an image or video, used as a strip, is changed by some application outside of Blender,
Blender has no real way of being notified from your operating system.
框显所选
Zoom and position the bounding box of the selected image into the center of the preview.
适应窗口预览 Home
Resize the preview so that it fits in the area.
区域缩放 Shift-B
点击并拖动绘制一个矩形，然后会缩放到这个矩形大小。
分（倍）数缩放
从1:8到8:1逐步调整预览大小。
缩放以适应
Automatically zoom preview image to make it fully fit the region.
