php实现高效获取图片尺寸的方法

本文实例讲述了php实现高效获取图片尺寸的方法。分享给大家供大家参考。具体分析如下：

php 获取图片尺寸的方法我们可以使用 getimagesize 获取图片尺寸，但是效率是很低的,首先需要获取整个的图片信息,然后再进行操作,下面的例子更科学算法更好,我们一起来看看吧.

方法可以用于快速获取图片尺寸信息,获取JPEG格式图片的尺寸信息,并且不需要下载读取整个图片,经测试这个函数不是对所有JPEG格式的图片都有效.

1.获取JPEG格式图片的尺寸信息,代码如下:

<?php 

/* 

* https://3water.com

*/ 

 

// Retrieve JPEG width and height without downloading/reading entire image. 

function getjpegsize($img_loc) { 

    $handle = fopen($img_loc, "rb") or die("Invalid file stream."); 

    $new_block = NULL; 

    if(!feof($handle)) { 

        $new_block = fread($handle, 32); 

        $i = 0; 

        if($new_block[$i]=="xFF" && $new_block[$i+1]=="xD8" && $new_block[$i+2]=="xFF" && $new_block[$i+3]=="xE0") { 

            $i += 4; 

            if($new_block[$i+2]=="x4A" && $new_block[$i+3]=="x46" && $new_block[$i+4]=="x49" && $new_block[$i+5]=="x46" && $new_block[$i+6]=="x00") { 

                 

// Read block size and skip ahead to begin cycling through blocks in search of SOF marker 

 

                $block_size = unpack("H*", $new_block[$i] . $new_block[$i+1]); 

                $block_size = hexdec($block_size[1]); 

                while(!feof($handle)) { 

                    $i += $block_size; 

                    $new_block .= fread($handle, $block_size); 

                    if($new_block[$i]=="xFF") { 

                         

// New block detected, check for SOF marker 

 

                        $sof_marker = array("xC0", "xC1", "xC2", "xC3", "xC5", "xC6", "xC7", "xC8", "xC9", "xCA", "xCB", "xCD", "xCE", "xCF"); 

                        if(in_array($new_block[$i+1], $sof_marker)) { 

                             

// SOF marker detected. Width and height information is contained in bytes 4-7 after this byte. 

 

                            $size_data = $new_block[$i+2] . $new_block[$i+3] . $new_block[$i+4] . $new_block[$i+5] . $new_block[$i+6] . $new_block[$i+7] . $new_block[$i+8]; 

                            $unpacked = unpack("H*", $size_data); 

                            $unpacked = $unpacked[1]; 

                            $height = hexdec($unpacked[6] . $unpacked[7] . $unpacked[8] . $unpacked[9]); 

                            $width = hexdec($unpacked[10] . $unpacked[11] . $unpacked[12] . $unpacked[13]); 

                            return array($width, $height); 

                        } else { 

                             

// Skip block marker and read block size 

 

                            $i += 2; 

                            $block_size = unpack("H*", $new_block[$i] . $new_block[$i+1]); 

                            $block_size = hexdec($block_size[1]); 

                        } 

                    } else { 

                        return FALSE; 

                    } 

                } 

            } 

        } 

    } 

    return FALSE; 

} 

?>

2.实例代码如下:

$url='http://www.xxxx.com/images/1331189004_28093400.jpg'; 

$image_content = file_get_contents($url); 

$image = imagecreatefromstring($image_content); 

$width = imagesx($image); 

$height = imagesy($image); 

echo $width.'*'.$height."nr";

希望本文所述对大家的PHP程序设计有所帮助。