PHP 更新 imagettftext() 和 imagefttext() 函数的字距调整问题

Question

我们的开发服务器最近升级到 PHP v5.2.13。通过这次升级，我们发现我们的 png 图像存在字距调整（字母间距）问题。我们尝试了多种字体，但尚未找到解决方案。

我们使用 GD 库创建图像，并使用字体文件和 imagettftext() 或 imagefttext() 函数将文本写入图像。

还有其他人遇到过这个吗？我是否误解了什么，或者应该将其作为错误提交给 PHP？有什么我还没有想到的很酷的解决方法吗？

这是新旧 tahoma 粗体的示例。其他字体（粗体和非粗体）也有同样的问题。有些字母和数字看起来像是偏离中心或类似的东西。

坏 - 新 PHP

好 - 旧 PHP v5.2.11 （用词略有不同，因为这是我们的开发服务器，另一个是实时服务器）

Answer 1

“跟踪”是一个类似的术语，表示文本设置的松紧程度。您可能会更好地通过谷歌搜索，例如 此结果。

Answer 2

由于我们使用的字体，字距调整对我们不起作用，因此我们必须对特定字母组合（如 AV、AW 等）进行手动字距调整。

/**
 * This function lets you write a string with your own letter spacing ($t)
 * and kern specific letter combinations like AV
 * 
 * @param type $im An image resource, returned by one of the image creation functions
 * @param type $size The font size. Depending on your version of GD, this should be specified as the pixel size (GD1) or point size (GD2).
 * @param type $angle The angle in degrees, with 0 degrees being left-to-right reading text. Higher values represent a counter-clockwise rotation. For example, a value of 90 would result in bottom-to-top reading text.
 * @param type $t Letter Spacing
 * @param type $k Kerning Spacing
 * @param type $x The coordinates given by x and y will define the basepoint of the first character (roughly the lower-left corner of the character). This is different from the imagestring(), where x and y define the upper-left corner of the first character. For example, "top left" is 0, 0.
 * @param type $y The y-ordinate. This sets the position of the fonts baseline, not the very bottom of the character.
 * @param type $color The color index. Using the negative of a color index has the effect of turning off antialiasing. See imagecolorallocate().
 * @param type $font The path to the TrueType font you wish to use.
 * @param type $text Text to write/print to the image
 */
function ImageTTFTextWithSpacing($im, $size, $angle, $t, $k, $x, $y, $color, $font, $text) {
    $numchar = strlen($text);
    for($i = 0; $i < $numchar; $i++) {
        # Assign character
        $char[$i] = substr($text, $i, 1);

        //Top is wider than bottom of character
        $up = ['Y','V','W'];
        //Bottom is wider than top of character
        $down = ['A'];
        //From the second letter on
        if( $i > 0 && 
                //check whether we have TOP and BOTTOM type character 
                //next to each other so we need to adjust spacing
                ((in_array($char[$i], $up) && in_array($char[$i-1], $down)) || 
                (in_array($char[$i-1], $up) && in_array($char[$i], $down)) )) {
            $w -= $k;
        }

        # Write character
        imagettftext($im, $size, $angle, ($x + $w + ($i * $t)), $y, $color, $font, $char[$i]);

        # Get width of character
        $width = imagettfbbox($size, $angle, $font, $char[$i]);
        $w = $w + $width[2];
    }
}