Mewa User's Guide/Getting started

From Wikibooks, open books for an open world
Jump to navigation Jump to search

Importing footage[edit]

Mewa performs operations over images, and these can be still images or videos. For a more generic term we will call it footage.

Let's start importing footage by clicking OpenButton.png in the action bar. This will open the File Browser. Click then on grid view button GridViewButton.png at the top of the File Browser to view thumbnails.

Below is a screenshot of Mewa with the File Browser open.

Open footage dialog

With the File Browser it's possible to load video files and image sequences as well. An image sequence is a group of files which are consecutively numbered.

Thumbnails are immediatly available to image sequences.

For video files a convert button is shown. That's because the file needs to be converted into a Mewa friendly format. Click on the convert button to start the conversion. Once the conversion is complete a thumbnail of the video file is shown.

Converted video files and image sequences show a slider just below the thumbnail. Use it to scroll through the different frames.

Press ok after selecting the footage you wish to import.

Once the footage has been imported it appears as a new node in the node graph.

Creating a node graph[edit]

We have now our first node in the node graph, a footage node.

Let's view how the footage node is layed out in the timeline. Click on ShowCurveEditorButton.png to expand the timeline and see the curve editor. At the top of the curve editor there is the curve or bar switch BarCurvesSwitch.png. This switch button offers the choice to see curves as curves or horizontal bars. Click on the button on the right, the bars buttons. An horizontal bar is shown. See the screenshot below.

Add footage to the node graph

The horizontal bar's length is exactly the number of frames in the footage file.

Every footage node can be independently positioned in the timeline. Dragging the footage bar changes the time the footage start. The footage length can be trimmed by dragging the right edge of the bar. It's also possible to hold the first frame by adjusting the left handler of the bar.

Now let's add an effect to our footage node. In the action bar, at the top, click on the node library button NodeLibraryButton.png to see the list of available nodes.

Node library button

Select the HexagonalPixelate option. A new node called hexagonalPixelate0 is shown next to the footage button.

Nodes can be dragged and moved anywhere inside the nodegraph window. Drag the hexagonalPixelate0 node below the footage node. To apply the HexagonalPixelate effect on the footage node connect the footage node output to the input of hexagonalPixelate0 as shown in the spicture below. Connections describe the workflow execution. The workflow is executed in a top down order, from outputs to inputs.

Inside the nodes there are 2 buttons. On the left side, with a rectangular shape is the output button. On the right side, with a circular shape is the parameters button. With the node buttons we can inspect the output of nodes. The parameter button opens the node's parameters window containing all the modifyable parameters of the node.

Node graph with hexagonal pixelate

Node Output[edit]

Clicking on the output button of hexagonalPixelate0 node (the square button on the left side of the node) the output window opens showing the output of hexagonalPixelate0 node.

The output window shows the output image of the last clicked output button.

Notice that the output image has a red rectangle around it. The red rectangle represents the output size. Processing operations are preformed inside the red rectangle only.

That size is set in the bottom right corner of the output window. The output size determines the output image size of all nodes.

Using the node graph[edit]

The node graph provides a top down "schematic" view of operations applied over images. With an image (footage node) as the top most node, image processing operations are performed by the connected nodes below. Image data is passed top-down, from one node to the next node connected to it. This structure of nodes illustrates the operations and the order of operations applied.

The advantage of using a node graph is it makes possible to edit the parameters of any node while visualizing the output of any node simultaneously.

Back to contents page