Power BI Automatic Font Color Selection

gistfile1.txt

CF Autoformat Font = 

// based on Ed Freeman's blog entry// https://endjin.com/blog/2020/06/how-to-dynamically-choose-the-correct-font-colour-based-on-a-background-colour-in-power-bi-tables

// 1. Grab the background colour for the current row (you will need to change the [CF Rank] measure to whatever measure returns your conditional formatting background color hex codes

VAR selectedColour = [CF Rank]

// 2. Extract the hexadecimal value for each digit in each colour couplet, and translate to the decimal representation of that value

VAR redDig1 = MID(selectedColour, 2, 1)
VAR redDig1Number = SWITCH(redDig1,"0",0,"1",1,"2",2,"3",3,"4",4,"5",5,"6",6,"7",7,"8",8,"9",9,"A",10,"B",11,"C",12,"D",13,"E",14,"F",15) 
VAR redDig2 = MID(selectedColour, 3, 1)
VAR redDig2Number = SWITCH(redDig2,"0",0,"1",1,"2",2,"3",3,"4",4,"5",5,"6",6,"7",7,"8",8,"9",9,"A",10,"B",11,"C",12,"D",13,"E",14,"F",15) 
VAR greenDig1 = MID(selectedColour, 4, 1)
VAR greenDig1Number = SWITCH(greenDig1,"0",0,"1",1,"2",2,"3",3,"4",4,"5",5,"6",6,"7",7,"8",8,"9",9,"A",10,"B",11,"C",12,"D",13,"E",14,"F",15) 
VAR greenDig2 = MID(selectedColour, 5, 1)
VAR greenDig2Number = SWITCH(greenDig2,"0",0,"1",1,"2",2,"3",3,"4",4,"5",5,"6",6,"7",7,"8",8,"9",9,"A",10,"B",11,"C",12,"D",13,"E",14,"F",15) 
VAR blueDig1 = MID(selectedColour, 6, 1)
VAR blueDig1Number = SWITCH(blueDig1,"0",0,"1",1,"2",2,"3",3,"4",4,"5",5,"6",6,"7",7,"8",8,"9",9,"A",10,"B",11,"C",12,"D",13,"E",14,"F",15) 
VAR blueDig2 = MID(selectedColour, 7, 1)
VAR blueDig2Number = SWITCH(blueDig2,"0",0,"1",1,"2",2,"3",3,"4",4,"5",5,"6",6,"7",7,"8",8,"9",9,"A",10,"B",11,"C",12,"D",13,"E",14,"F",15) 

// 3. Assign the value of the Gamma exponent

VAR gamma = 2.2

// 4. Calculate the RGB values and normalize

VAR redNumber = ((redDig1Number * 16) + redDig2Number) / 255
VAR greenNumber = ((greenDig1Number * 16) + greenDig2Number) / 255
VAR blueNumber = ((blueDig1Number * 16) + blueDig2Number) / 255

// 5. Apply calculation as per Stack Exchange answer

VAR luminance = (0.2126 * POWER(redNumber, gamma)) + (0.7152 * POWER(greenNumber, gamma)) + (0.0722 * POWER(blueNumber, gamma))

// 6. If the luminance is greater than 0.5, return "Black". Else return "White".

RETURN 
  SWITCH(TRUE(),
    selectedColour = "Transparent", "Black",
    ISBLANK( selectedColour ), "Black",
    luminance > 0.5, "Black",
   "White"
)