PHP implementation of generating PNG thumbnail function with transparent background sharing, png thumbnail_PHP tutorial

PHP implements sharing of PNG thumbnail function for generating transparent background, png thumbnail

I wrote a PHP function to generate thumbnails in the WEB development notes before. Although that function can generate thumbnails, it has certain flaws. When generating PNG thumbnails, the background is black. I wrote another function today. Come make amends. The code is very simple, that is, imagealphablending($thumb,false); and imagesavealpha($thumb,true); are very important. The main thing is to save the alpha value of PNG and not lose it.

The function is as follows:

<&#63;PHP
/*
 *$sourePic:原图路径
 * $smallFileName:小图名称
 * $width:小图宽
 * $heigh:小图高
 * 转载注明 www.chhua.com*/
function pngthumb($sourePic,$smallFileName,$width,$heigh){
	$image=imagecreatefrompng($sourePic);//PNG
		 	imagesavealpha($image,true);//这里很重要 意思是不要丢了$sourePic图像的透明色;
		 	$BigWidth=imagesx($image);//大图宽度
			$BigHeigh=imagesy($image);//大图高度
			$thumb = imagecreatetruecolor($width,$heigh);
			imagealphablending($thumb,false);//这里很重要,意思是不合并颜色,直接用$img图像颜色替换,包括透明色;
			imagesavealpha($thumb,true);//这里很重要,意思是不要丢了$thumb图像的透明色;
			if(imagecopyresampled($thumb,$image,0,0,0,0,$width,$heigh,$BigWidth,$BigHeigh)){
			imagepng($thumb,$smallFileName);}
			return $smallFileName;//返回小图路径 转载注明 www.chhua.com
}
 
pngthumb("a.png", "c.png", 300, 300);//调用
&#63;>

Use PHOTOSHOP to do it, cut out what you need and make a copy, then delete the background layer and save it as PNG

Note

1: After judging the image, prepare it for output or save before using the method imagecreatefromjpeg

2: imagesy($src_img); Please consider using list($width,$ height) = getimagesize($src_img);

3: $ratio_h=1.0 * $new_height / $h;//n=unknown number, 1 multiplied by any n, the result is still n, why do we do this ?

4: Your program receives external input dimensions, which will cause the output or saved pictures to be distorted and deformed

5: $ratio=1.0;
if($ratio_w < ;=1 && $ratio_h <= 1) {
if($ratio_w < $ratio_h){}else {}//Note 4: Consider using the ternary algorithm

6: $inter_h= (int) ($new_height /$ratio);//PHP is not as sensitive to data types as Java, so there is no need to use int to force conversion

7: Remember to destroy the image after processing imagedestroy();

Finally: You can explain the effect you want