exif_thumbnail()

(PHP 4 >= 4.2.0, PHP 5, PHP 7)

取得嵌入在 TIFF 或 JPEG 图像中的缩略图

说明

exif_thumbnail(string $filename[,int &$width[,int &$height[,int &$imagetype]]]): string

exif_thumbnail()读取TIFF或JPEG图像中的嵌入缩略图。如果图像不包含缩略图则返回FALSE。

If you want to deliver thumbnails through this function, you should send the mimetype information using the header() function.

It is possible that exif_thumbnail() cannot create an image but can determine its size. In this case, the return value is FALSE but$widthand$heightare set.

参数

$filename

The name of the image file being read. This image contains an embedded thumbnail.

$width

The return width of the returned thumbnail.

$height

The returned height of the returned thumbnail.

$imagetype

The returned image type of the returned thumbnail. This is either TIFF or JPEG.

返回值

Returns the embedded thumbnail, or FALSE if the image contains no thumbnail.

更新日志

范例

exif_thumbnail()例子

<?php
if (array_key_exists('file',$_REQUEST)) {
    $image = exif_thumbnail($_REQUEST['file'], $width, $height, $type);
} else {
    $image = false;
}
if ($image!==false) {
    header("Content-type: ".image_type_to_mime_type($type));
    echo $image;
    exit;
} else {
    // no thumbnail available, handle the error here
    echo "No thumbnail available";
}
?>

参见

• exif_read_data()从 JPEG 或 TIFF 文件中读取 EXIF 头信息
• image_type_to_mime_type()取得 getimagesize，exif_read_data，exif_thumbnail，exif_imagetype 所返回的图像类型的 MIME 类型

use this if you want to embed a thumbnail directly on the HTML page without writing it first to a file:
<?php
$image = exif_thumbnail($file, $width, $height, $type);
echo "<img width='$width' height='$height' src='data:image/gif;base64,".base64_encode($image)."'>";
?>

This will allow you to manipulate the thumbnail image ($imgJpeg) using the various gd commands:
<?php
 if (($imgJpeg = exif_thumbnail($strImagePath)) === false)
  print "No Thumbnail!";
 else
  $imgJpeg = imageCreateFromString($imgJpeg);
?>

If you've edited the image with image editing software and it no longer contains an exif thumbnail, I've created a script that will add one back into it, using the "PHP Exif Library": http://pel.sourceforge.net/index.php
<?php
require_once('../PEL/PelJpeg.php');
require_once('../PEL/PelIfd.php');
$fullpath = 'images/DSC_0013c.JPG'; # path of source image (does not contain an exif thumbnail)
   
$jpeg = new PelJpeg($fullpath);
 $exif = $jpeg->getExif();
 $tiff = $exif->getTiff();
 $ifd0 = $tiff->getIfd();    # need this so that we can later link it to the new IFD 
 $ifd1 = $ifd0->getNextIfd();
if (!$ifd1) {    # Only create thumbnail if one doesn't exist (i.e. there is no IFD1)
  $ifd1 = new PelIfd(1);
  $ifd0->setNextIfd($ifd1); # point ifd0 to the new ifd1 (or else ifd1 will not be read)
  $original = ImageCreateFromString($jpeg->getBytes()); # create image resource of original
  $orig_w=imagesx($original);
  $orig_h=imagesy($original);
  $wmax = 160;
  $hmax = 120;
  if ($orig_w>$wmax || $orig_h>$hmax) {
    $thumb_w=$wmax;
    $thumb_h=$hmax;
    if ($thumb_w/$orig_w*$orig_h>$thumb_h)
      $thumb_w=round($thumb_h*$orig_w/$orig_h); # maintain aspect ratio
    else
      $thumb_h=round($thumb_w*$orig_h/$orig_w);
  }
  else { # only set the thumb's size if the original is larger than 'wmax'x'hmax'
    $thumb_w=$orig_w;
    $thumb_h=$orig_h;
  }
    # create image resource with thumbnail sizing
  $thumb=imagecreatetruecolor($thumb_w,$thumb_h); 
    ## Resize original and copy to the blank thumb resource
  imagecopyresampled($thumb,$original,
                0,0,0,0,$thumb_w,$thumb_h,$orig_w,$orig_h);
    # start writing output to buffer
  ob_start();    
    # outputs thumb resource contents to buffer
  ImageJpeg($thumb);  
    # create PelDataWindow from buffer thumb contents (and end output to buffer)
  $window = new PelDataWindow(ob_get_clean()); 
  if ($window) {  
    $ifd1->setThumbnail($window); # set window data as thumbnail in ifd1
    $outpath = $fullpath; # overwrite original jpg file
    file_put_contents($outpath, $jpeg->getBytes()); # write everything to output filename
      # Show thumbnail in file:
    echo '<img src="thumb_exif.php?image='.$outpath.'" border=0 alt="If you see this, it did not work"><br>';
    
  }
}
else {
  echo 'ifd1 already exists! (IFD1 is where the thumbnail is stored)<br>';
}
?>
<?php # This is the code in thumb_exif.php :
    $imgdat = exif_thumbnail($_REQUEST['image'], $width, $height, $type);
    header('Content-type: ' . image_type_to_mime_type($type));
    echo($imgdat);
?>
If you have a lot of such files, you can easily make a script that searches them out and adds thumbnails to their exif.

If you want to convert from TIFF to JPG you can use ImageMagick if it is installed in your server.
<?php
$exec = 'convert /path/to/file.tiff /path/to/file.jpg 2>&1';
@exec($exec, $exec_output, $exec_retval);
//possible error
print_r($exec_output)
?>

Great that the thumbnail can be in TIFF format (f.i. Kodak cameras have embedded thumbnail in TIFF) BUT I have not been able to show TIFF as an embedded image in HTML (using the <IMG...> tag). There seems to be no function in PHP to change TIFF to, lets say, JPG. (imagecreatefromstring gives a 'unknown datatype' error for the TIFF stream. So below sample works great for JPEG embedded thumbnail, but not for TIFF embedded (but then, maybe I did something wrong?):
test_exif.php:
<HTML>
<HEAD>
  <TITLE>Test EXIF Read </TITLE>
</HEAD>
<BODY>
<?php
$image='P0000614.JPG';
echo("<B>". $image. "</B>:<BR><BR>\n");
$exif = exif_read_data($image, 'ANY_TAG',true);
if (!$exif===false)
{
  echo("Image contains headers<br><br>");
  echo("<A href=showthumb.php?image=" . $image ."> <IMG border=0 src=showthumb.php?image=" . $image ."></A><BR><BR>");
  foreach ($exif as $key => $section) 
  {
    foreach ($section as $name => $val) 
    {
      echo "$key.$name: $val<br>\n";
    }
  }
}
else
{
  echo("Sorry, image <B>".$image . "</B> does not contain (readable) EXIF data.");
}
?>
</BODY>
</HTML>
showthumb.php:
<?php
$imgdat = exif_thumbnail($_REQUEST['image'],$width, $height, $type);
header('Content-type: ' . image_type_to_mime_type($type));
echo($imgdat);
?>
When clicking on the <A> opens the TIFF image in the program that windows assigned to this type, but the JPEG opens in the browser.
I am using PHP 4.3.6 on windows iis 4 (yeah, I know.....)