How do I modify the behaviour of "Image Sizing" Module in Export

Question

As part of the export process I want to re-size an image to a fixed size e.g., 5400x3600. The iamge should be scaled symmetrically and therefore some fill-in of black or white may be necessary.
I know I can do this as a "post-process" action, but then I need to re-do sharpening, assigning colour profile etc.
So is there a way in the SDK to "replace" the "Image Sizing" Module with one of my own making?
Best wishes
Terry

Answer 1

You can disable the image sizing portion of the UI and use the updateExportSettings() function on your export service provider to force the image size to your desired size. (This function is not well documented. It takes a single parameter, exportSettings, which you may modify in place before the export starts.) For example (this would go inside your export service provider declaration):
updateExportSettings = function( exportSettings )
    exportSettings.LR_size_resizeType = 'wh'  -- specific width and height
    exportSettings.LR_maxHeight = 3600
    exportSettings.LR_maxWidth = 5400
end,
hideSections = { 'imageSettings' },  -- hide the sizing panel
However, there is not a way to get Lightroom to render a file that is cropped to a specific aspect ratio. Whatever sizing parameters are specified, we will always honor the aspect ratio of the source file. In your processRenderedFiles function, you could use a third-party tool like Mogrify to regenerate the output file with the fill necessary to satisfy the desired aspect ratio.