php - 用php旋转png图像后如何获得透明背景？

Question

所以我有 png 图像并旋转它但我得到黑色背景..或者如果我使用白色的颜色代码我会变成白色..我试过这样做..

$trans = imagecolorallocatealpha(image, 0, 0, 0, 127);
imagerotate($image, $degree, $trans)

我也试过..

$trans = imagecolorallocatealpha($image, 255, 255, 255, 127);

有人可以帮帮我吗？

这是我的代码.. 如果我将 allocatealpha 更改为 0, 0, 255, 0 然后它会变成蓝色。但是 0, 0, 0, 127 它仍然是黑色的。

function rotate($degrees) {
    $image = $this->image;
    imagealphablending($image, false);
    $color = imagecolorallocatealpha($image, 0, 0, 0, 127);
    imagefill($this->image, 0, 0, $color);
    $rotate = imagerotate($image, $degrees, $color);
    imagesavealpha($image, TRUE);
    $this->image = $rotate;
}

Answer 1

$destimg = imagecreatefromjpeg("image.png");
$transColor = imagecolorallocatealpha($destimg, 255, 255, 255, 127);
$rotatedImage = imagerotate($destimg, 200, $transColor);
imagesavealpha($rotatedImage, true);
imagepng($rotatedImage,"rotated.png");

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根据下面的正确评论，这应该是:

$destimg = imagecreatefrompng("image.png");
$transColor = imagecolorallocatealpha($destimg, 255, 255, 255, 127);
$rotatedImage = imagerotate($destimg, 200, $transColor);
imagesavealpha($rotatedImage, true);
imagepng($rotatedImage,"rotated.png");