Question: After georeferencing a black and white TIFF image, the QGIS Raster Georeferencer fills the corners with black pixels, creating black elongated triangles along the edges of the new image. I could not find anything in the Georeferencer settings to force these filler pixels to be while. I want to set all white pixels transparent when importing the image into QGIS, so eliminating the black corners is preferred. I tried editing the georeferenced TIFF image but it loses the reference data on saving. I tried the GeoTIFF tools (listgeo.exe and geotifcp.exe) but writing the data back to the TIFF image using geotifcp.exe gives a warning "LZW compression is not available to due to Unisys patent enforcement." It would be ideal if QGIS can be set to force the padding colour to white otherwise I am happy to try any other tools, methods or instructions how to achieve what I want.

[![Black borders added to georeferenced image marked in red X](https://i.stack.imgur.com/XYn2N.png)](https://i.stack.imgur.com/XYn2N.png)

Answer: 
It's a super hack, but it works.

1. Do the georeferencing as normal.
2. Open the created \_modified.tif file in Paint.NET (<https://www.getpaint.net/download.html>) FREE!
3. Bucket fill the black corner triangles with white. Save file as new TIFF (just in case).
4. Drag-drop new TIFF into QGIS. It'll maintain the georeferencing and now have white corners.
In the Georeferencer, check the 'Use 0 for transparency when needed' which will make the black pixels go away. To avoid white pixels, go to Layer properties and set 255 as the additional nodata value.
[![enter image description here](https://i.stack.imgur.com/7bCKX.png)](https://i.stack.imgur.com/7bCKX.png)