如何旋轉圖像，並使用PHP GD

Question

使用旋轉圖像，下面的代碼與透明背景調整和調整大小相同，

<?php 

$src = "41611326.png"; 

// Get new dimensions 
list($width, $height) = getimagesize($src); 

$new_width = 192; 
$new_height = 192; 
$dstimage=imagecreatetruecolor($new_width,$new_height); 

$srcimage = imagecreatefrompng($src); 

$degrees = -30; 

$srcimage = imagerotate($srcimage, $degrees, 0) ; 

imagealphablending($dstimage, false); 
imagesavealpha($dstimage, true); 

imagecopyresampled($dstimage,$srcimage,0,0,0,0, $new_width,$new_height,$width,$height); 

header('Content-type: image/png') ; 
imagepng($dstimage) ; 

?> 

但其輸出圖像沒有得到透明背景。如何保持透明背景。

請任何幫助

Answer 1

我認爲你需要使用imagecolortransparent（）函數。

Documentation

Answer 2

變化：

$srcimage = imagerotate($srcimage, $degrees, 0) ; 

到：

$srcimage = imagerotate($srcimage, $degrees, -1); 

Answer 3

function rotate_transparent_img($img_resource, $angle){ 

    $pngTransparency = imagecolorallocatealpha($img_resource , 0, 0, 0, 127); 
    imagefill($img_resource , 0, 0, $pngTransparency); 

    $result = imagerotate($img_resource, $angle, $pngTransparency); 
    imagealphablending($result, true); 
    imagesavealpha($result, true); 

    return $result; 
} 

用法：

$img_resource = imagecreatefrompng('transparent_img.png'); 
$angle = 30; 

$res = rotate_transparent_img($img_resource, $angle); 
header('Content-Type: image/png'); 
imagepng($res);