Tuesday Whiteboard: reflections and edges


We were looking at finding a value for the intercept of a straight line graph when the scale of the graph made it difficult to have an X axis that started at zero – we were setting up and solving a simple equation within a context.

This second whiteboard processed using ScanR was taken in a difficult room with windows facing the whiteboard and bright reflections. ScanR is a Web based service that processes your mobile phone pictures of whiteboards or documents into PDF files, see Monday’s post for details. Much to my surprise, the reflections were not a problem – it was the edge detection that proved problematic…


ScanR seems to have taken the graph Y axis as the edge of the whiteboard and ignored marks to the left. Another shot taken at an angle (originally taken to avoid bright reflections) happened to include the edge of the whiteboard and wasn’t cropped….


As the left edge of the whiteboard is visible, this is processed by ScanR as follows…


This scan can be exported from the Mac OS X Preview application as a TIFF and cropped if needed. All the images above have been resized in Photoshop Elements to 400 pixels wide – the originals had higher resolution.

The moral is: don’t worry about reflections, ScanR can deal with those very well, just make sure there is a frame or edge to the whiteboard work so that ScanR can pick up the true extent of the image.

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