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This tutorial demonstrates how TheGIMP and TheGIMPAnimation Plug-in's Video Navigator work on a stack of video extracted images also called frames.

When you open an image from the stack of frames and right click through the menus to Video -->Video Navigator what used to be a simple gimp image window turns into a special window with a memory buffer.

This tutorial will cover a few basic functions this dialog can be used for. Making the thumbnails quickly, changing frames in the special image window and deleting frames.

If you are using the movie provided for this tutorial, the first frame and the first time you see the Video Navigator it probably looks much like the image here. Don't panic.

Make Thumbnails Quickly

Shift the keyboard and push the button with the triangle in the middle of the circle in the Video Navigator dialog and your thumbnails will all become updated.

Change the Image in the Special Image window

Double clicking on a frame in the Video Navigator will "send" that frame to the special image window.

Looking at the second frame this way, it was a relief to discover that only the first frame had the weird and wrong coloring.

According to Hof, author of the plug-in: "this is a known bug of the ffmpeg video encoder backend in the video api ... (for some ffmpeg codecs the 1.st guess what type of YUV colormodel is used is wrong, the real type is known after reading the 1.st frame. a workaround in the video API that always reads the 1. frame twice is planed)"

Delete a frame

Deleting a frame from the layer stack is not a trivial idea. Deleting it via the Video Navigator Dialog will also cause all of the frame names (each image in the frame stack) to be renamed to reflect the deletion.

Pushing the button on the dialog is easy. Just select the frame to be deleted by highlighting it or group of frames by using the shift key when highlighting the frames and push the button with the trash icon on it. GAP will pause while it deletes the frame and updates the names of the other frames. The pause could last a long time depending on the strength and speed of your computer and the number of frames that need to be changed.

GAP also lets you know what it is doing on the special image window progress bar.

The Layers Dialog

The special window still behaves the expected way in TheGIMP's own layers dialog. Looking at the modified frame stack in the Layers Dialog it is good to note two things:

1. The layer is still named Frame00002 even though the image has been renamed to mvi_000001.xcf
2. Each of the remaining images in the frame stack is a background image that will need to have an alpha channel added to it before any masking can be accomplished.