Hex transparency in colors [duplicate]
Here's a correct table of percentages to hex values. E.g. for 50% white you'd use #80FFFFFF.
- 100% — FF
- 95% — F2
- 90% — E6
- 85% — D9
- 80% — CC
- 75% — BF
- 70% — B3
- 65% — A6
- 60% — 99
- 55% — 8C
- 50% — 80
- 45% — 73
- 40% — 66
- 35% — 59
- 30% — 4D
- 25% — 40
- 20% — 33
- 15% — 26
- 10% — 1A
- 5% — 0D
- 0% — 00
(source)
Short answer
You can see the full table of percentages to hex values and run the code in this playground in https://play.golang.org/p/l1JaPYFzDkI .
Short explanation in pseudocode
Percentage to hex values
- decimal = percentage * 255 / 100 . ex : decimal = 50*255/100 = 127.5
- convert decimal to hexadecimal value . ex: 127.5 in decimal = 7*16ˆ1 + 15 = 7F in hexadecimal
Hex values to percentage
- convert the hexaxdecimal value to decimal. ex: D6 = 13*16ˆ1 + 6 = 214
- percentage = (value in decimal ) * 100 / 255. ex : 214 *100/255 = 84%
More infos for the conversion decimal <=> hexadecimal
Long answer: how to calculate in your head
The problem can be solved generically by a cross multiplication.
We have a percentage (ranging from 0 to 100 ) and another number (ranging from 0 to 255) then converted to hexadecimal.
- 100 <==> 255 (FF in hexadecimal)
- 0 <==> 0 (00 in hexadecimal)
For 1%
- 1 * 255 / 100 = 2,5
- 2,5 in hexa is 2 if you round it down.
For 2%
- 2 * 255 / 100 = 5
- 5 in hexa is 5 .
The table in the best answer gives the percentage by step of 5%.
How to calculate the numbers between in your head ? Due to the 2.5 increment, add 2 to the first and 3 to the next
- 95% — F2 // start
- 96% — F4 // add 2 to F2
- 97% — F7 // add 3 . Or F2 + 5 = F7
- 98% — F9 // add 2
- 99% — FC // add 3. 9 + 3 = 12 in hexa : C
- 100% — FF // add 2
I prefer to teach how to find the solution rather than showing an answer table you don't know where the results come from.
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