PHP GD库文本渲染与像素化

Question

这是文本覆盖在图像上的问题，渐变在文本周围有一些奇怪的像素化，但我无法理解为什么。

- ＆gt;

以下是代码：

<?php
function hex2rgb($hex) {
    $rgb[0] = hexdec(substr($hex, 0, 2));
    $rgb[1] = hexdec(substr($hex, 2, 2));
    $rgb[2] = hexdec(substr($hex, 4, 2));
    return $rgb;
}

$sourceImage = imagecreatefromstring(file_get_contents("source.jpg"));

$imagePadding = 10;

$height = imagesy($sourceImage);
$width = imagesx($sourceImage);

$baseImage = imagecreatetruecolor($width, $height);

$backgroundColor = imagecolorallocate($baseImage, 0, 0, 0);
imagefill($baseImage, 0, 0, $backgroundColor);

imagecopyresampled($baseImage, $sourceImage, 0, 0, 0, 0, $width, $height, $width, $height);

//==== GRADIENT ====//
// Modified from: http://stackoverflow.com/questions/14684622/blend-transparent-gradient-with-an-image-using-php-gd-library
$gradientCanvas = imagecreatetruecolor($width, $height);
$transColor = imagecolorallocatealpha($gradientCanvas, 0, 0, 0, 127);

imagefill($gradientCanvas, 0, 0, $transColor);

$color = hex2rgb("000000");
$start = -40;
$stop = 120;
$range = $stop - $start;

for ($y = 0; $y < $height; ++$y) {
    $alpha = $y <= $start ? 0 : round(min(($y - $start) / $range, 1) * 127);
    $newColor = imagecolorallocatealpha($gradientCanvas, $color[0], $color[1], $color[2], $alpha);
    imageline($gradientCanvas, 0, $y, $width, $y, $newColor);
}

imagecopyresampled($baseImage, $gradientCanvas, 0, 0, 0, 0, $width, $height, $width, $height);

//==== TEXT ====//
putenv('GDFONTPATH=.');
$font = "HelveticaNeueBold.ttf";


$white = imagecolorallocate($baseImage, 255, 255, 255);
imagettftext($baseImage, 14, 0, $imagePadding, $imagePadding + 16, $white, $font, "Foobar");

header('Content-Type: image/jpeg');
imagejpeg($baseImage);
imagedestroy($baseImage);
imagedestroy($sourceImage);
?>

Answer 1

主要原因 - 您使用JPG作为输出和输入图像。编辑JPG图像通常会导致图像失真。尝试使用PNG图像作为源。 或者尝试将imagejpeg（）的“quality”参数设置为100

Answer 2

imagejpeg http://php.net/manual/en/function.imagejpeg.php的默认质量为~75，您需要将其设置为100

imagejpeg($baseImage, null, 100);