PHP Implementation of PNG Thumbnail Function Sharing for Generating Transparent Background

Before, I wrote an PHP thumbnail generation function in WEB development notes. Although that function can generate thumbnails, it has a definite defect. When generating PNG thumbnails, the background is black. Today, I wrote another function to make up for it. The code is simple, that is, imagealphablending ($thumb, false); With imagesavealpha ($thumb, true); It is very important. The main thing is to save the alpha value of PNG, and don't lose it.

The function is as follows:

<?PHP
/*
 *$sourePic: Original path 
 * $smallFileName: Small picture name 
 * $width: Small picture width 
 * $heigh: Small figure height 
 *  Reproduced note  www.chhua.com*/
function pngthumb($sourePic,$smallFileName,$width,$heigh){
	$image=imagecreatefrompng($sourePic);//PNG
		 	imagesavealpha($image,true);// It's important here   It means don't lose it $sourePic Transparent color of image ;
		 	$BigWidth=imagesx($image);// Large graph width 
			$BigHeigh=imagesy($image);// Height of large map 
			$thumb = imagecreatetruecolor($width,$heigh);
			imagealphablending($thumb,false);// It's important here , It means not to merge colors , Direct use $img Image color replacement , Includes transparent colors ;
			imagesavealpha($thumb,true);// It's important here , It means don't lose it $thumb Transparent color of image ;
			if(imagecopyresampled($thumb,$image,0,0,0,0,$width,$heigh,$BigWidth,$BigHeigh)){
			imagepng($thumb,$smallFileName);}
			return $smallFileName;// Returns the path of the small picture   Reproduced note  www.chhua.com
}
 
pngthumb("a.png", "c.png", 300, 300);// Call 
?>