imagerotate()中的背景透明性 [英] Background transperancy in imagerotate()

问题描述

最近两天以来，我一直在尝试使用imagerotate()PHP-GD函数旋转图像后向背景添加透明度.

Since last 2 days, I was trying to add transperancy to the background after rotating an image using imagerotate() PHP-GD function.

但是，令我非常失望的是，它根本没有用.

But, to my great disappointment, it's not working at all.

它只是在它后面散发出黑色背景.

It's just giving out a black background behind it.

这是我的代码-

$patchImageS    =   'image.png'; // the image to be patched over the final bg
$patchImage =   imagecreatefrompng($patchImageS); // resource of image to be patched
$patchImage     =   imagerotate($patchImage, 23, 0, 0);
imagepng($patchImage,'tt.png');

我试图将函数中传递的参数更改为

I tried to change the parameters being passed in function to

imagerotate($ patchImage，23，5，0);

imagerotate($patchImage, 23, 5, 0);

imagerotate($ patchImage，23，0，5);

imagerotate($patchImage, 23, 0, 5);

任何帮助将不胜感激.

推荐答案

在完成99％的回答后，这是我找到的解决方案:

After a number of 99% finished answers, here's the solution I've found:

// Create, or create from image, a PNG canvas
$png = imagecreatetruecolor($width, $height);

// Preserve transparency
imagesavealpha($png , true);
$pngTransparency = imagecolorallocatealpha($png , 0, 0, 0, 127);
imagefill($png , 0, 0, $pngTransparency);

// Rotate the canvas including the required transparent "color"
$png = imagerotate($png, $rotationAmount, $pngTransparency);

// Set your appropriate header
header('Content-Type: image/png');

// Render canvas to the browser
imagepng($png);

// Clean up
imagedestroy($png);

关键是要在imagerotate()调用中包含imagecolorallocatealpha()...

The key here is to include your imagecolorallocatealpha() in your imagerotate() call...

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