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Merging images
==============

With the merge node you are able to control how your images are combined.

Layering Images Together with the Merge Node
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1.  	Select Merge > Merge (or press M in the Node Graph) to insert a Merge node after the images you want to layer together.
2.  	Connect your images to the Merge node’s **A** and **B** inputs. 
3.  	Connect a Viewer to the output of the Merge node so you can see the effect of your merge operation.

.. image:: _images/compositing-Merging_images_00.png


4.  	In the Merge node’s controls, select how you want to layer the images together from the operation dropdown menu. The most common operation is **over**, which layers input **A** over input **B** according to the alpha of input **A**. Just click through the various operations to figure out what they are doing. 

.. image:: _images/compositing-Merging_images_01.png


5.    Set which input's bounding box you want to use for the Merge output: 

.. image:: _images/compositing-Merging_images_02.png


* **union** - resize the output b box to fit both input bboxes completely.
* **intersection** - use only those parts of the image where the input bboxes overlap.
* **A or B** - use the selected input's bbox for the output.



6. With using the **A Channels** and **B Channels** checkboxes you may select which color and alpha channels to use and to output.

7. The **Mix** slider is used to fade/mix in the image from input **A**.


.. note:: **A** is always the foreground layer. **B** is always the background layer. 



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