php - 如何允许使用 php 上传透明 gif 或 png

Question

我在下面有这个功能，可以让我调整上传图片的大小，

function resize_image($image,$width,$height,$scale) 
{
    list($imagewidth, $imageheight, $imageType) = getimagesize($image);
    $imageType = image_type_to_mime_type($imageType);
    $newImageWidth = ceil($width * $scale);
    $newImageHeight = ceil($height * $scale);
    $newImage = imagecreatetruecolor($newImageWidth,$newImageHeight);

    switch($imageType) 
    {
        case "image/gif":
            $source = imagecreatefromgif($image); 
            break;
        case "image/pjpeg":
        case "image/jpeg":
        case "image/jpg":
            $source = imagecreatefromjpeg($image); 
            break;
        case "image/png":
        case "image/x-png":
            $source = imagecreatefrompng($image); 
            break;
    }

    imagecopyresampled($newImage,$source,0,0,0,0,$newImageWidth,$newImageHeight,$width,$height);

    switch($imageType) 
    {
        case "image/gif":
            imagegif($newImage,$image); 
            break;
        case "image/pjpeg":
        case "image/jpeg":
        case "image/jpg":
            imagejpeg($newImage,$image,90); 
            break;
        case "image/png":
        case "image/x-png":
            imagepng($newImage,$image);  
            break;
    }

    chmod($image, 0777);
    return $image;
}

但是这个函数有一个问题，就是当我有一个透明背景的png或gif时，它不能创建透明度。

如何修复此功能以允许 php 透明化？

Answer 1

这是我的答案，

# This is the resizing/resampling/transparency-preserving magic
    if ( ($imageType == "image/gif") || ($imageType == "image/png") ) 
    {
        $transindex = imagecolortransparent($source);

        if($transindex >= 0) 
        {
            $transcol = imagecolorsforindex($source, $transindex);
            $transindex = imagecolorallocatealpha($newImage, $transcol['red'], $transcol['green'], $transcol['blue'], 127);
            imagefill($newImage, 0, 0, $transindex);
            imagecolortransparent($newImage, $transindex);
        }

        elseif ($imageType == "image/png" || $imageType == "image/x-png") 
        {
            imagealphablending($newImage, false);
            $color = imagecolorallocatealpha($newImage, 0, 0, 0, 127);
            imagefill($newImage, 0, 0, $color);
            imagesavealpha($newImage, true);
        }
    }

而且工作得很好