在 PHP 中,将 RGB 三元组转换为 HSV 值的最直接方法是什么?
最佳答案
这是一个简单直接的方法,它以度数和百分比的形式返回 HSV 值,这是 Photoshop 的颜色选择器使用的。
请注意,返回值不会四舍五入,如果需要,您可以自己进行。请记住 H(360) == H(0)
,因此 359.5
及更大的 H
值应四舍五入为 0
大量记录用于学习目的。
/**
* 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);
}
?>
关于php - PHP中的RGB到HSV,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/1773698/