Asked  7 Months ago    Answers:  5   Viewed   46 times

What would be a good way to convert hex color values like #ffffff into the single RGB values 255 255 255 using PHP?

 Answers

67

Check out PHP's hexdec() and dechex() functions: http://php.net/manual/en/function.hexdec.php

Example:

$value = hexdec('ff'); // $value = 255
Wednesday, March 31, 2021
 
Gilko
answered 7 Months ago
23

Note: both versions of rgbToHex expect integer values for r, g and b, so you'll need to do your own rounding if you have non-integer values.

The following will do to the RGB to hex conversion and add any required zero padding:

function componentToHex(c) {
  var hex = c.toString(16);
  return hex.length == 1 ? "0" + hex : hex;
}

function rgbToHex(r, g, b) {
  return "#" + componentToHex(r) + componentToHex(g) + componentToHex(b);
}

alert(rgbToHex(0, 51, 255)); // #0033ff

Converting the other way:

function hexToRgb(hex) {
  var result = /^#?([a-fd]{2})([a-fd]{2})([a-fd]{2})$/i.exec(hex);
  return result ? {
    r: parseInt(result[1], 16),
    g: parseInt(result[2], 16),
    b: parseInt(result[3], 16)
  } : null;
}

alert(hexToRgb("#0033ff").g); // "51";

Finally, an alternative version of rgbToHex(), as discussed in @casablanca's answer and suggested in the comments by @cwolves:

function rgbToHex(r, g, b) {
  return "#" + ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1);
}

alert(rgbToHex(0, 51, 255)); // #0033ff

Update 3 December 2012

Here's a version of hexToRgb() that also parses a shorthand hex triplet such as "#03F":

function hexToRgb(hex) {
  // Expand shorthand form (e.g. "03F") to full form (e.g. "0033FF")
  var shorthandRegex = /^#?([a-fd])([a-fd])([a-fd])$/i;
  hex = hex.replace(shorthandRegex, function(m, r, g, b) {
    return r + r + g + g + b + b;
  });

  var result = /^#?([a-fd]{2})([a-fd]{2})([a-fd]{2})$/i.exec(hex);
  return result ? {
    r: parseInt(result[1], 16),
    g: parseInt(result[2], 16),
    b: parseInt(result[3], 16)
  } : null;
}

alert(hexToRgb("#0033ff").g); // "51";
alert(hexToRgb("#03f").g); // "51";
Tuesday, June 1, 2021
 
Joegramming
answered 5 Months ago
83

Real answer: Depends on what kind of hexadecimal color value you are looking for (e.g. 565, 555, 888, 8888, etc), the amount of alpha bits, the actual color distribution (rgb vs bgr...) and a ton of other variables.

Here's a generic algorithm for most RGB values using C++ templates (straight from ScummVM).

template<class T>
uint32 RGBToColor(uint8 r, uint8 g, uint8 b) {
return T::kAlphaMask |
       (((r << T::kRedShift) >> (8 - T::kRedBits)) & T::kRedMask) |
       (((g << T::kGreenShift) >> (8 - T::kGreenBits)) & T::kGreenMask) |
       (((b << T::kBlueShift) >> (8 - T::kBlueBits)) & T::kBlueMask);
}

Here's a sample color struct for 565 (the standard format for 16 bit colors):

template<>
struct ColorMasks<565> {
enum {
    highBits    = 0xF7DEF7DE,
    lowBits     = 0x08210821,
    qhighBits   = 0xE79CE79C,
    qlowBits    = 0x18631863,


    kBytesPerPixel = 2,

    kAlphaBits  = 0,
    kRedBits    = 5,
    kGreenBits  = 6,
    kBlueBits   = 5,

    kAlphaShift = kRedBits+kGreenBits+kBlueBits,
    kRedShift   = kGreenBits+kBlueBits,
    kGreenShift = kBlueBits,
    kBlueShift  = 0,

    kAlphaMask = ((1 << kAlphaBits) - 1) << kAlphaShift,
    kRedMask   = ((1 << kRedBits) - 1) << kRedShift,
    kGreenMask = ((1 << kGreenBits) - 1) << kGreenShift,
    kBlueMask  = ((1 << kBlueBits) - 1) << kBlueShift,

    kRedBlueMask = kRedMask | kBlueMask

};
};
Wednesday, June 9, 2021
 
keyBeatz
answered 5 Months ago
65

It seems your code is obfuscated not only with hex escape sequences, but with octal as well. I've written this function to decode it for you:

function decode_code($code){
    return preg_replace_callback(
        "@\(x)?([0-9a-f]{2,3})@",
        function($m){
            return chr($m[1]?hexdec($m[2]):octdec($m[2]));
        },
        $code
    );
}

See it in action here: http://codepad.viper-7.com/NjiL84

Friday, July 30, 2021
 
muncherelli
answered 3 Months ago
48

How about these:

function rgbaToRgb ($rgba, $blend = 0xFFFFFF) {
    return (($rgba >> 8)*($rgba & 0xFF)/0xFF) * ($blend / 0xFFFFFF);
}

function rgbToRgba ($rgb) {
    return ($rgb << 8) | 0xFF;
}

$blend in the first is effectively a background color to blend with.

Edit: fix due to not enough space in ints ruining RGBA. RGBA is now handled as a four part array. RGB remains a number.:

function rgbaToRgb ($rgba, $blend = 0xFFFFFF) {
$rbg = array($rgba[0] * $rgba[3]/0xFF + ($blend>>16) * (0xFF-$rgba[3])/0xFF, $rgba[1] * $rgba[3]/0xFF + (($blend>>8)&0xFF)*(0xFF-$rgba[3])/0xFF, $rgba[2] * $rgba[3]/0xFF + ($blend&0xFF) * (0xFF-$rgba[3])/0xFF);
return ($rbg[0]<<16) + ($rbg[1]<<8) + $rbg[2];
}

function rgbToRgba ($rgb) {
    return array($rgb >> 16, ($rgb >> 8) & 0xFF, $rgb & 0xFF, 0xFF);
}
Saturday, August 21, 2021
 
Pachvarsh
answered 2 Months ago
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