更改“色相" PHP GD Library生成图像的过程? [英] Change "HUE" of an image with PHP GD Library?

问题描述

我想使用PHP图像处理功能更改图像的色相".哪个是正确的过滤器?

I'd like to change the "hue" of an image using the PHP image processing functions. Which is the correct filter to apply?

注意:我来自Photoshop背景，因此，如果我对色相"的解释与其他人不同，这就是我的意思...

Note: I'm from a photoshop background, so in the event my interpretation of "hue" is different from others, here's what I mean...

在photoshop中，您可以使用色调"滤镜更改图像的颜色，而不会实际影响图像的设计.

In photoshop, you can use the "Hue" filter to change the color of an image without actually affecting the design of the image.

我目前正在使用下面的功能为图像重新着色，但是由于该功能完全重新绘制了图像而丢失了设计，因此该功能无法满足我的需求.

I'm currently using the function below to recolor my images, but the function fails to meet my needs due to the fact that it completely repaints the image, losing the design.

    function set_theme_color_header($hex)
    {
        $info = hexToRGB($hex); //utility function that converts hex to rgb
        $token = "header.gif";
        $img = imagecreatefromgif("header-template.gif";
        $color = imagecolorallocate($img, $info["red"], $info["green"], $info["blue"]);
        imagecolorset($img, 0, $info["red"], $info["green"], $info["blue"]);
        imagegif($img, $token);
    }
    ?>

推荐答案

我很确定PHP中没有可以处理色调变化的函数.但是您可以编写自己的函数来执行此操作，以下是更改图像色调的步骤:

I'm pretty sure there are no functions in PHP that can handle the change of hue. But you can write your own function to do this, here are the steps to change the image's hue:

1. 逐像素遍历图像
2. 使用 imagecolorat()
获取像素处的RGB颜色
3. 将RGB值转换为HSL值
4. 更改色相值，不设置饱和度和亮度(色相值介于0到360之间)
5. 将新的HSL值转换回RGB
6. 更改当前像素的颜色

1. Traverse the image pixel by pixel
2. Get the RGB color at pixel using imagecolorat()
3. Transform the RGB value into a HSL value
4. Change the hue value, leave saturation and lightness alone (Hue is a value from 0 to 360)
5. Transform the new HSL value back to RGB
6. Change the color at current pixel

实际上，尝试一下似乎很有趣，因此，如果您找不到其他解决方案，我可以自己做，然后将其发布在这里.

Actually this seems quite an interesting thing to try out, so I might just do this myself and post it here if you don't find any other solution.

编辑

编写功能.要在PHP中更改色相，您将需要在RGB和HSL颜色空间之间进行转换的函数，以及用于遍历图像的函数.这可能有点难看，但效果很好.在较大的图像上相当慢.

Wrote the function. To change hue in PHP, you'll need functions to transform between RGB and HSL color spaces and a function that does the traversing of the image. This might be a bit ugly but it works nicely. Quite slow on larger images.

function imagehue(&$image, $angle) {
    if($angle % 360 == 0) return;
    $width = imagesx($image);
    $height = imagesy($image);

    for($x = 0; $x < $width; $x++) {
        for($y = 0; $y < $height; $y++) {
            $rgb = imagecolorat($image, $x, $y);
            $r = ($rgb >> 16) & 0xFF;
            $g = ($rgb >> 8) & 0xFF;
            $b = $rgb & 0xFF;            
            $alpha = ($rgb & 0x7F000000) >> 24;
            list($h, $s, $l) = rgb2hsl($r, $g, $b);
            $h += $angle / 360;
            if($h > 1) $h--;
            list($r, $g, $b) = hsl2rgb($h, $s, $l);            
            imagesetpixel($image, $x, $y, imagecolorallocatealpha($image, $r, $g, $b, $alpha));
        }
    }
}

以下是转换色彩空间所需的帮助器功能，该功能可以从 http://www.actionscript.org/forums/showthread.php3?t=50746 进行了一些细微改动:

Here's the required helper functions for converting color space, shamelessly copied from http://www.actionscript.org/forums/showthread.php3?t=50746 with minor alterations:

function rgb2hsl($r, $g, $b) {
   $var_R = ($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--;
   }

   return array($h, $s, $v);
}

function hsl2rgb($h, $s, $v) {
    if($s == 0) {
        $r = $g = $B = $v * 255;
    } else {
        $var_H = $h * 6;
        $var_i = floor( $var_H );
        $var_1 = $v * ( 1 - $s );
        $var_2 = $v * ( 1 - $s * ( $var_H - $var_i ) );
        $var_3 = $v * ( 1 - $s * (1 - ( $var_H - $var_i ) ) );

        if       ($var_i == 0) { $var_R = $v     ; $var_G = $var_3  ; $var_B = $var_1 ; }
        else if  ($var_i == 1) { $var_R = $var_2 ; $var_G = $v      ; $var_B = $var_1 ; }
        else if  ($var_i == 2) { $var_R = $var_1 ; $var_G = $v      ; $var_B = $var_3 ; }
        else if  ($var_i == 3) { $var_R = $var_1 ; $var_G = $var_2  ; $var_B = $v     ; }
        else if  ($var_i == 4) { $var_R = $var_3 ; $var_G = $var_1  ; $var_B = $v     ; }
        else                   { $var_R = $v     ; $var_G = $var_1  ; $var_B = $var_2 ; }

        $r = $var_R * 255;
        $g = $var_G * 255;
        $B = $var_B * 255;
    }    
    return array($r, $g, $B);
}

最后是一个用法示例.本示例打开图像，将其色相偏移180°.并输出到浏览器:

And finally, an usage example. This example opens an image, shifts its hue by 180° and outputs to the browser:

header('Content-type: image/png');
$image = imagecreatefrompng('image.png');
imagehue($image, 180);
imagepng($image);

由于将色相角度设置为度，所以将0、360、720或360的任意倍数设置都不会改变图像.

As the angle of hue is set in degrees, giving 0, 360, 720 or any multiple of 360 will result in no change to the image.

这篇关于更改“色相" PHP GD Library生成图像的过程?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！