php png水印不透明的方法：首先通过“public function water(){...}”给图片添加水印；然后通过“imagecolorallocate($wImage...);”等函数防止png透明背景变黑即可。
本文操作环境：Windows7系统、PHP7.1版，DELL G3电脑
php图片添加水印（水印png图片透明处变黑）
首先是给图片添加水印，该函数的使用很简单，写的很详细
/**
* 为图片添加水印
* @static public
* @param string $source 原文件名
* @param string $water 水印图片
* @param string $$savename 添加水印后的图片名
* @param string $alpha 水印的透明度
* @return void
*/
public function water($source, $water, $savename=null, $alpha=80 ,$w_pos = 9) {
//检查文件是否存在
if (!file_exists($source) || !file_exists($water))
return false;
//图片信息
$sInfo = self::getImageInfo($source);
$wInfo = self::getImageInfo($water);
//如果图片小于水印图片，不生成图片
if ($sInfo["width"] < $wInfo["width"] || $sInfo['height'] < $wInfo['height'])
return false;
//建立图像
$sCreateFun = "imagecreatefrom" . $sInfo['type'];
$sImage = $sCreateFun($source);
$wCreateFun = "imagecreatefrom" . $wInfo['type'];
$wImage = $wCreateFun($water); //$wImage
//2.上色 //防止png透明背景变黑
$color=imagecolorallocate($wImage,255,255,255);
//3.设置透明
imagecolortransparent($wImage,$color);
imagefill($wImage,0,0,$color);
//设定图像的混色模式
imagealphablending($wImage, true);
//imageAlphaBlending($wImage, false);
//imageSaveAlpha($wImage, true);
//图像位置,默认为右下角右对齐
//$posY = $sInfo["height"] - $wInfo["height"];
//$posX = $sInfo["width"] - $wInfo["width"];
switch($w_pos) {
case 1:
$wx = 5;
$wy = 5;
break;
case 2:
$wx = ($sInfo["width"] - $wInfo["width"]) / 2;
$wy = 0;
break;
case 3:
$wx = $sInfo["width"] - $wInfo["width"];
$wy = 0;
break;
case 4:
$wx = 0;
$wy = ($sInfo["height"] - $wInfo["height"]) / 2;
break;
case 5:
$wx = ($sInfo["width"] - $wInfo["width"]) / 2;
$wy = ($sInfo["height"] - $wInfo["height"]) / 2;
break;
case 6:
$wx = $sInfo["width"] - $wInfo["width"];
$wy = ($sInfo["height"] - $wInfo["height"]) / 2;
break;
case 7:
$wx = 0;
$wy = $sInfo["height"] - $wInfo["height"];
break;
case 8:
$wx = ($sInfo["width"] - $wInfo["width"]) / 2;
$wy = $sInfo["height"] - $wInfo["height"];
break;
case 9:
$wx = $sInfo["width"] - $wInfo["width"];
$wy = $sInfo["height"] - $wInfo["height"];
break;
case 10:
$wx = rand(0,($sInfo["width"] - $wInfo["width"]));
$wy = rand(0,($sInfo["height"] - $wInfo["height"]));
break;
default:
$wx = $sInfo["width"] - $wInfo["width"];
$wy = $sInfo["height"] - $wInfo["height"];
break;
}
//生成混合图像
imagecopymerge($sImage, $wImage, $wx, $wy, 0, 0, $wInfo['width'], $wInfo['height'], $alpha);
//输出图像
$ImageFun = 'Image' . $sInfo['type'];
//如果没有给出保存文件名，默认为原图像名
if (!$savename) {
$savename = $source;
@unlink($source);
}
//保存图像
$ImageFun($sImage, $savename);
imagedestroy($sImage);
}补充，上面的函数中需要用到下面这个函数
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/**
* 取得图像信息
* @static
* @access public
* @param string $image 图像文件名
* @return mixed
*/
static function getImageInfo($img) {
$imageInfo = getimagesize($img);
if ($imageInfo !== false) {
$imageType = strtolower(substr(image_type_to_extension($imageInfo[2]), 1));
$imageSize = filesize($img);
$info = array(
"width" => $imageInfo[0],
"height" => $imageInfo[1],
"type" => $imageType,
"size" => $imageSize,
"mime" => $imageInfo['mime']
);
return $info;
} else {
return false;
}
}
后来会遇到这样的问题————当水印有透明底色时，生成的图片背景为黑色；
如图
这样就需要对水印图片做一下处理，如下
//2.上色 //防止png透明背景变黑
$color=imagecolorallocate($wImage,255,255,255);
//3.设置透明
imagecolortransparent($wImage,$color);
imagefill($wImage,0,0,$color);这样再进行加水印的操作就可以了
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