php生成图片缩略图的函数_PHP教程

$a=thumbImage('1.jpg',200,100,'2.jpg');//将1.jpg生成宽为200，高为100的缩略图，并保存为2.jpg
print_r($a);

$a=thumbImage('1.jpg',200,100);//将1.jpg生成宽为200，高为100的缩略图，并直接覆盖1.jpg，不生成新图片

<?php
/*
*php生成图片缩略图的函数
*www.phpernote.com
*/
function thumbImage($file,$thumbWidth,$thumbHeight,$savePath='',$isCut=true,$quality=100){
	$result=array('status'=>0,'file'=>'','width'=>0,'height'=>0,'savePath'=>'','info'=>'');
	if(!file_exists($file)){
		return array('status'=>1,'file'=>'','width'=>0,'height'=>0,'savePath'=>'','info'=>'图片文件不存在');
	}
	//检测文件类型
	$fp=fopen($file,'rb');
	$str=fread($fp,2); //只读2字节
	fclose($fp);
	$str=@unpack("c2chars",$str);
	$typeCode=intval($str['chars1'].$str['chars2']);
	$fileType='';
	switch($typeCode){
		case 255216:
			$fileType='jpg';
		break;
		case 7173:
			$fileType='gif';
		break;
		case 6677:
			$fileType='bmp';
		break;
		case 13780:
			$fileType='png';
		break;
		default:
			$fileType=$typeCode;
		break;
	}
	if($str['chars1']=='-1'&&$str['chars2']=='-40'){
		$fileType='jpg';
	}
	if($str['chars1']=='-119'&&$str['chars2']=='80'){
		$fileType='png';
	}
	if(!in_array($fileType,array('jpg','gif','bmp','png'))){
		return array('status'=>2,'file'=>'','width'=>0,'height'=>0,'savePath'=>'','info'=>'图片文件类型不正确:'.$fileType);
	}
	//图片缩放处理
	if($fileType=='jpg'){
		$im=imagecreatefromjpeg($file);
	}
	if($fileType=='gif'){
		$im=imagecreatefromgif($file);
	}
	if($fileType=='png'){
		$im=imagecreatefrompng($file);
	}
	if(empty($savePath))
	$savePath=$file;
	$width=imagesx($im);
	$height=imagesy($im);
	if($width<$thumbWidth&&$height<$thumbHeight){
		return array('status'=>3,'file'=>'','width'=>0,'height'=>0,'savePath'=>'','info'=>'图片尺寸小于生成缩略图的尺寸');
	}
	$ratio=$width/$height;//实际图象的比例
	$thumbRatio=$thumbWidth/$thumbHeight;//改变后的图象的比例
	if($isCut){//裁切处理
		if(function_exists('imagepng')&&(str_replace('.','',PHP_VERSION)>=512)){//针对php版本大于5.12参数变化后的处理情况
			$quality=9;
		}
		if($ratio>=$thumbRatio){//高度优先
			$newimg=imagecreatetruecolor($thumbWidth,$thumbHeight);
			imagecopyresampled($newimg,$im,0,0,0,0,$thumbWidth,$thumbHeight,(($height)*$thumbRatio),$height);
			imagejpeg($newimg,$savePath,$quality);
		}
		if($ratio<$thumbRatio){//宽度优先
			$newimg=imagecreatetruecolor($thumbWidth,$thumbHeight);
			imagecopyresampled($newimg,$im,0,0,0,0,$thumbWidth,$thumbHeight,$width,(($width)/$thumbRatio));
			imagejpeg($newimg,$savePath,$quality);
		}
	}else{//不裁切处理
		if($ratio>=$thumbRatio){
			$newimg=imagecreatetruecolor($thumbWidth,($thumbWidth)/$ratio);
			imagecopyresampled($newimg,$im,0,0,0,0,$thumbWidth,($thumbWidth)/$ratio,$width,$height);
			imagejpeg($newimg,$savePath,$quality);
		}
		if($ratio<$thumbRatio){
			$newimg=imagecreatetruecolor(($thumbHeight)*$ratio,$thumbHeight);
			imagecopyresampled($newimg,$im,0,0,0,0,($thumbHeight)*$ratio,$thumbHeight,$width,$height);
			imagejpeg($newimg,$savePath,$quality);
		}
	}
	ImageDestroy($im);//www.phpernote.com/php-function/1007.html
	return array('status'=>0,'file'=>$file,'width'=>$thumbWidth,'height'=>$thumbHeight,'savePath'=>$savePath,'info'=>'缩略图片生成成功');
}