如何使用php上传透明的gif或png

问题描述 投票:2回答:4

我在下面具有此功能,可让我调整上传图像的大小,

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;
}

但是此函数有一个问题,当我有透明背景的png或gif时,它无法创建透明。

如何修复此功能以允许PHP透明?

php transparency gd2 imagecreatefrompng
4个回答
4
投票

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);
        }
    }

而且工作还不错


3
投票

我发现此解决方案非常有帮助!

http://www.php.net/manual/ru/function.imagecopyresampled.php#104028

您只需要在imagecreatetruecolor()和imagecopyresampled()之间添加此代码。不要忘记定义$ type。

$newImage = imagecreatetruecolor($newImageWidth,$newImageHeight);

// preserve transparency
if($type == "gif" || $type == "png"){
  imagecolortransparent($newImage, imagecolorallocatealpha($newImage, 0, 0, 0, 127));
  imagealphablending($newImage, false);
  imagesavealpha($newImage, true);
}

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

1
投票

查看开源的smart_resize_image方法,似乎他们检查了imagecolortransparent,如果存在,则将其重新应用于新图像。

也许值得一看,在github上签出该项目,而不是重新发明轮子。还为您提供了有关其工作方式的一些见解,并且是协作的工作(很多人在解决已知[和未知]错误的工作)。


0
投票

为了使GD Lib绘制透明,必须定义透明的颜色。您可以在图形上的某处采样颜色,然后使用它。

imagecolortransparent

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