php旋转图像的透明度

Question

我发现有几篇关于在php中旋转图像的文章。但是，它们都将图像的透明部分变为黑色。

旋转时替换的部分是透明的（imagerotate函数$transparency变量工作正常，但原始图像本身不会保持透明。在此图像中，白色区域（替换为imagerotate）应该是透明的，但黑色区域也应该是透明的：

感谢您的帮助。我的代码如下。

<?php

//$mapim=imagecreatefrompng('http://maps.googleapis.com/maps/api/staticmap?center=40.039299261014,-76.112831236771&zoom=20&size=600x600&sensor=false&maptype=satellite');
$panel=base64_decode('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');

//ob_start();
$degrees=60;
$srcpanelim=imagecreatefromstring($panel);
$panelim=imagecreatetruecolor(600,600);
$transparency = imagecolorallocatealpha($panelim,0,0,0,127);
imagealphablending( $panelim, false );
imagesavealpha( $panelim, true );
imagecopyresampled($panelim,$srcpanelim,0,0,0,0,600,600,600,600);
ob_start();
    imagepng($panelim, NULL, 9);
    $rawImageBytes = ob_get_clean();
    echo "<img src='data:image/png;base64,".base64_encode($rawImageBytes ) . "' />";
$transparency = imagecolorallocatealpha($panelim,0,0,0,127);
$panelim = imagerotate( $panelim, $degrees, $transparency, 1);

ob_start();
//header( 'Content-Type: image/png' );
imagepng( $panelim );
$rawImageBytes = ob_get_clean();
    echo "<img src='data:image/png;base64,".base64_encode($rawImageBytes ) . "' />";  
imagedestroy( $panelim );

/*$panelim
ob_start();
    imagepng($panelim, NULL, 9);
    $rawImageBytes = ob_get_clean();
    echo "<img src='data:image/png;base64,".base64_encode($rawImageBytes ) . "' />";
    */


?>

Answer 1

使用Imagecopy合并而不是imagecopyresampled。 Imagecopyresample与imagecopy以及其他重新采样相同。这里的问题是iamgecopy不适用于透明度。

你可以在php.net上找到关于这个的说明： http://www.php.net/manual/en/function.imagecolortransparent.php