: Catalogue image comparison

Gaffer introduces the ability to compare two images from a Catalogue in the Image Viewer. Over, Under, Difference and Replace modes are supported, as well as the ability to wipe between images.

Comparing Images

The currently selected image in the Catalogue is used on the ‘A’ side of the comparison, and up to 4 images from the same Catalogue can be assigned an Output Index which makes them available for use on the ‘B’ side of the comparison.

An Output Index is assigned by clicking in the Catalogue’s new Output Index column. Left clicking in this column will assign output index 1, while other indices can be assigned via the right click menu.

Clicking on an existing output index will remove the assignment.

Image comparison can then be enabled in the Viewer by selecting a comparison mode from the Compare Mode menu.

Enabling comparison mode also enables the wipe. The wipe can be positioned by clicking and dragging anywhere along the line representing its edge, and can be rotated by clicking and dragging on the semicircular handle at its midpoint.

The wipe can be disabled by clicking on the Wipe button immediately to the right of the Compare Mode menu.

By default the selected image will be compared with Output Index 1. Other outputs can be compared by selecting them from the Catalogue Output menu.


Comparison can be toggled with the Q shortcut. The currently selected comparison mode will be maintained when toggled.

The wipe can be toggled with the W shortcut. The current wipe position will be preserved when toggled.


The CatalogueSelect node is also Output Index aware, allowing it to select an image from a Catalogue based on its assigned output index.

For example, this could be used to set up an interactive slap comp where Output Index 3 is used as the foreground image, and Output Index 4 is used as the background image. The choice of background and foreground image in the slap comp could then be controlled by assigning the appropriate output index to the required images in the Catalogue.

Limitations and Future Improvements

Currently only two images from the same Catalogue node can be compared. We aim to extend this in the future to also support comparisons between two image nodes. (Update: This was addressed in Gaffer

The colour inspector will only display colour information for the ‘A’ side of the comparison, though we intend to support display of pixel values from both images being compared. (Update: This was addressed in Gaffer Release Notes

The full list of new features, improvements, and fixes released in Gaffer can be found here.

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