RGB a HSV en PHP

Question

En PHP, ¿cuál es la forma más directa de convertir un triplete RGB a valores HSV?

Answer 1

<?php 
function RGB_TO_HSV ($R, $G, $B) // RGB Values:Number 0-255 
{         // HSV Results:Number 0-1 
    $HSL = array(); 

    $var_R = ($R/255); 
    $var_G = ($G/255); 
    $var_B = ($B/255); 

    $var_Min = min($var_R, $var_G, $var_B); 
    $var_Max = max($var_R, $var_G, $var_B); 
    $del_Max = $var_Max - $var_Min; 

    $V = $var_Max; 

    if ($del_Max == 0) 
    { 
     $H = 0; 
     $S = 0; 
    } 
    else 
    { 
     $S = $del_Max/$var_Max; 

     $del_R = ((($var_Max - $var_R)/6) + ($del_Max/2))/$del_Max; 
     $del_G = ((($var_Max - $var_G)/6) + ($del_Max/2))/$del_Max; 
     $del_B = ((($var_Max - $var_B)/6) + ($del_Max/2))/$del_Max; 

     if  ($var_R == $var_Max) $H = $del_B - $del_G; 
     else if ($var_G == $var_Max) $H = (1/3) + $del_R - $del_B; 
     else if ($var_B == $var_Max) $H = (2/3) + $del_G - $del_R; 

     if ($H<0) $H++; 
     if ($H>1) $H--; 
    } 

    $HSL['H'] = $H; 
    $HSL['S'] = $S; 
    $HSL['V'] = $V; 

    return $HSL; 
} 

Answer 2

Aquí es un método simple y directo que devuelve valores como HSV grados y porcentajes, que es la que utiliza el selector de color de Photoshop.

Tenga en cuenta que los valores de retorno no son redondeados, puede hacerlo usted mismo si es necesario. Tenga en cuenta que H(360) == H(0), por lo H valores de 359.5 y mayor debe ronda a 0

fuertemente documentada con fines didácticos.

/** 
* Licensed under the terms of the BSD License. 
* (Basically, this means you can do whatever you like with it, 
* but if you just copy and paste my code into your app, you 
* should give me a shout-out/credit :) 
*/ 

<?php 

function RGBtoHSV($R, $G, $B) // RGB values: 0-255, 0-255, 0-255 
{        // HSV values: 0-360, 0-100, 0-100 
    // Convert the RGB byte-values to percentages 
    $R = ($R/255); 
    $G = ($G/255); 
    $B = ($B/255); 

    // Calculate a few basic values, the maximum value of R,G,B, the 
    // minimum value, and the difference of the two (chroma). 
    $maxRGB = max($R, $G, $B); 
    $minRGB = min($R, $G, $B); 
    $chroma = $maxRGB - $minRGB; 

    // Value (also called Brightness) is the easiest component to calculate, 
    // and is simply the highest value among the R,G,B components. 
    // We multiply by 100 to turn the decimal into a readable percent value. 
    $computedV = 100 * $maxRGB; 

    // Special case if hueless (equal parts RGB make black, white, or grays) 
    // Note that Hue is technically undefined when chroma is zero, as 
    // attempting to calculate it would cause division by zero (see 
    // below), so most applications simply substitute a Hue of zero. 
    // Saturation will always be zero in this case, see below for details. 
    if ($chroma == 0) 
     return array(0, 0, $computedV); 

    // Saturation is also simple to compute, and is simply the chroma 
    // over the Value (or Brightness) 
    // Again, multiplied by 100 to get a percentage. 
    $computedS = 100 * ($chroma/$maxRGB); 

    // Calculate Hue component 
    // Hue is calculated on the "chromacity plane", which is represented 
    // as a 2D hexagon, divided into six 60-degree sectors. We calculate 
    // the bisecting angle as a value 0 <= x < 6, that represents which 
    // portion of which sector the line falls on. 
    if ($R == $minRGB) 
     $h = 3 - (($G - $B)/$chroma); 
    elseif ($B == $minRGB) 
     $h = 1 - (($R - $G)/$chroma); 
    else // $G == $minRGB 
     $h = 5 - (($B - $R)/$chroma); 

    // After we have the sector position, we multiply it by the size of 
    // each sector's arc (60 degrees) to obtain the angle in degrees. 
    $computedH = 60 * $h; 

    return array($computedH, $computedS, $computedV); 
} 

?>