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Formatting SharePoint Columns with RGB Color

I wrote about ensuring high contrast between text and the background of Visio shapes in my last article. The RGB values actually came from an imported SharePoint list that has a lookup to a list that contains the RGB values of named colours. Having solved how to display the correct text colour for high contrast in Visio, I wanted to the same in a SharePoint column, but first I had to learn how to use the RGB values to format the background colour.

SharePointColumnColourFormat.png


My good friend Chris Roth, aka VisGuy, has already produced Visio ShapeSheet formulas to convert RGB values to Hex values. so I adaptively re-used his idea to create a formula that I could use in a SharePoint calculated column, called Hex.
First, I compressed his multiple User-defined Cells rows into a single formula:

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Ensuring High Contrast Text in Visio Shapes

I am working on a project where I need to ensure high contrast of the text in the Visio shapes for accessibility. At first, I attempted to write my own formula but a colleague pointed my to a website that confirms if the contrast is acceptable ( contrast-ratio.com ), and showed me that a few of my examples failed. So the search was on for a better formula than my own. This lead me to a Stack Exchange answer with just what I was looking for (Formula for Color Contrast between Text and Background). All I needed to do was to convert this into a ShapeSheet formula or two, and then I could apply it to the text inside the shapes.

VisioColorMap



Any text created with Data Graphic Text Callouts cannot have the high contrast formula applied to because they can be moved independent of the background. However any text added with Insert / Field inside the shape changes between black and white with respect to the FillForegnd value in its background.
Following the article above, it is necessary to calculate the lightness, L, of the FillForegnd, and then to check if black or white text is going to provide satisfactory contrast.

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