QRegEx to match a pure hue color

user_2359027 0
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I am creating a QLineEditor to manually input a color in hex format. I want to set a validator to check if the input color is a pure HUE color.

All hue colors follow this pattern, being X any hex character [from 0-9 or A-F]:

#FF00XX
#00FFXX
#00XXFF
#XX00FF
#XXFF00
#FFXX00

I managed to check for a correct HEX color value: ^#([A-Fa-f0-9]{6})$, but I don't know how to extend the validator to accept only hue colors.

Any ideas?

qregexp validation regex
3 Answers

The pattern you want is ^#(?:00(?:FFXX|XXFF)|FF(?:00XX|XX00)|XX(?:00FF|FF00))$.

If you want XX to be any hex char, replace with [a-fA-F0-9]{2}. Then, the regex will look like

^#(?:00(?:FF[a-fA-F0-9]{2}|[a-fA-F0-9]{2}FF)|FF(?:00[a-fA-F0-9]{2}|[a-fA-F0-9]{2}00)|[a-fA-F0-9]{2}(?:00FF|FF00))$

See the regex demo.

If you do not want XX to match 00 and FF, replace XX with (?![fF]{2}|00)[a-fA-F0-9]{2}. Then, the regex will look like

^#(?:00(?:FF(?![fF]{2}|00)[a-fA-F0-9]{2}|(?![fF]{2}|00)[a-fA-F0-9]{2}FF)|FF(?:00(?![fF]{2}|00)[a-fA-F0-9]{2}|(?![fF]{2}|00)[a-fA-F0-9]{2}00)|(?![fF]{2}|00)[a-fA-F0-9]{2}(?:00FF|FF00))$

See the regex demo.

The (?![fF]{2}|00)[a-fA-F0-9]{2} part matches any two hex chars that are not equal to FF or 00 (case insensitive).

user_38329700

The simplest way is to just use the pipe operator to cover all the six cases:

00[A-Fa-f0-9]{2}FF|00FF[A-Fa-f0-9]{2}|FF00[A-Fa-f0-9]{2}|FF[A-Fa-f0-9]{2}00|[A-Fa-f0-9]{2}00FF|[A-Fa-f0-9]{2}FF00

Demo

Obviously the pattern [A-Fa-f0-9]{2} is repeated several times. To remove redundancy, you can save it in a separate variable and use string formatting to substitute it and form the pattern as shown above.

user_29126650

If there are just 6 cases you can write this cases using boolean OR (|)

(?<=#00FF|#FF00)[A-Fa-f0-9]{2}|[A-Fa-f0-9]{2}(?=00FF|FF00)|(?<=#00)[A-Fa-f0-9]{2}(?=FF)|(?<=#FF)[A-Fa-f0-9]{2}(?=00)

Demo

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