如何将RGBA颜色代码转换为PHP中的8位十六进制？

发布于 2025-01-26 02:26:35 字数 1055 浏览 4 评论 0原文

我正在尝试转换一些 rgba 值值适用于适合变电站alpha字幕文件。 .ass文件格式需要一种颜色格式，例如＆amp; h12345690，其中十六进制字节为蓝色，绿色，红色，alpha顺序。

我发现将8位十六进制颜色转换为RGBA的示例，但不相反。这是我基于一个答案之一组合的函数，但是alpha频道始终返回为零：

function rgbtohex($string) {
    $string = str_replace("rgba","",$string);
    $string = str_replace("rgb","",$string);
    $string = str_replace("(","",$string);
    $string = str_replace(")","",$string);
    $colorexplode = explode(",",$string);    
    $hex = '&H';
    
    foreach($colorexplode AS $c) {
        echo "C" . $c . " " . dechex($c) . "<br><br>";
        $hex .= dechex($c);      
    }
    return $hex;
}

但是，如果我使用rgba（123,223,215，.9）进行测试，则会产生＆amp; H7BDFD70只有7个字符而不是8个字符。

此外，Alpha Channel（.9）始终达到零，因此似乎无法正常工作。

原文

I'm attempting to convert some rgba values into a format suitable for SubStation Alpha subtitle files. The .ass file format requires a colour format like &H12345690 where the hex bytes are in blue, green, red, alpha order.

I am finding examples converting 8 digit hex colors into RGBA, but not the other way around. Here is a function I put together based one of the answers, but the alpha channel is always returned as zero:

function rgbtohex($string) {
    $string = str_replace("rgba","",$string);
    $string = str_replace("rgb","",$string);
    $string = str_replace("(","",$string);
    $string = str_replace(")","",$string);
    $colorexplode = explode(",",$string);    
    $hex = '&H';
    
    foreach($colorexplode AS $c) {
        echo "C" . $c . " " . dechex($c) . "<br><br>";
        $hex .= dechex($c);      
    }
    return $hex;
}

But if I test it with rgba(123,223,215,.9) it produces &H7bdfd70 which only has 7 characters instead of 8.

Also, the alpha channel (.9) always comes out to zero, so that doesn't appear to be working correctly.

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行雁书 2025-02-02 02:26:35

您可以使用printf（）函数系列来转换为正确填充的十六进制字符串。小数不能在十六进制中表示，因此该值被视为0xff的分数。

$rgba = "rgba(123,100,23,.5)";

// get the values
preg_match_all("/([\\d.]+)/", $rgba, $matches);

// output
$hex = sprintf(
    "&H%02X%02X%02X%02X",
    $matches[1][2], // blue
    $matches[1][1], // green
    $matches[1][0], // red
    $matches[1][3] * 255, // adjusted opacity
);
echo $hex;

输出：

&H17647B7F

You can use the printf() family of functions to convert to a properly padded hex string. Decimals cannot be represented in hex, so the value is taken as a fraction of 0xFF.

$rgba = "rgba(123,100,23,.5)";

// get the values
preg_match_all("/([\\d.]+)/", $rgba, $matches);

// output
$hex = sprintf(
    "&H%02X%02X%02X%02X",
    $matches[1][2], // blue
    $matches[1][1], // green
    $matches[1][0], // red
    $matches[1][3] * 255, // adjusted opacity
);
echo $hex;

Output: