在 php 获取图片尺寸的方法我们可以使用 getimagesize 获取图片尺寸的效率是很低的,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:

1. <?php
2. /*
3. * http://www.phpfensi.com
4. */
5. // Retrieve JPEG width and height without downloading/reading entire image.
6. function getjpegsize($img_loc) {
7. $handle = fopen($img_loc, "rb") or die("Invalid file stream.");
8. $new_block = NULL;
9. if(!feof($handle)) {
10. $new_block = fread($handle, 32);
11. $i = 0;
12. if($new_block[$i]=="xFF" && $new_block[$i+1]=="xD8" && $new_block[$i+2]=="xFF" && $new_block[$i+3]=="xE0") {
13. $i += 4;
14. if($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") {
15. // Read block size and skip ahead to begin cycling through blocks in search of SOF marker
16. $block_size = unpack("H*", $new_block[$i] . $new_block[$i+1]);
17. $block_size = hexdec($block_size[1]);
18. while(!feof($handle)) {
19. $i += $block_size;
20. $new_block .= fread($handle, $block_size);
21. if($new_block[$i]=="xFF") {
22. // New block detected, check for SOF marker
23. $sof_marker = array("xC0", "xC1", "xC2", "xC3", "xC5", "xC6", "xC7", "xC8", "xC9", "xCA", "xCB", "xCD", "xCE", "xCF");
24. if(in_array($new_block[$i+1], $sof_marker)) {
25. // SOF marker detected. Width and height information is contained in bytes 4-7 after this byte.
26. $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];
27. $unpacked = unpack("H*", $size_data);
28. $unpacked = $unpacked[1];
29. $height = hexdec($unpacked[6] . $unpacked[7] . $unpacked[8] . $unpacked[9]);
30. $width = hexdec($unpacked[10] . $unpacked[11] . $unpacked[12] . $unpacked[13]);
31. return array($width, $height);
32. } else {
33. // Skip block marker and read block size
34. $i += 2;
35. $block_size = unpack("H*", $new_block[$i] . $new_block[$i+1]);
36. $block_size = hexdec($block_size[1]);
37. }
38. } else {
39. return FALSE;
40. }
41. }
42. }
43. }
44. }
45. return FALSE;
46. }
47. ?>

2.实例代码如下:

1. $url='http://www.phpfensi.com/images/201203/08/1331189004_28093400.jpg';
2. $image_content = file_get_contents($url);
3. $image = imagecreatefromstring($image_content);
4. $width = imagesx($image);
5. $height = imagesy($image);
6. echo $width.'*'.$height."nr";