PHP uses GD library to generate high-quality thumbnail image sample code

On the website, the GD library is usually used to generatethumbnails, or to add watermarks to pictures, or to generate Chinese charactersverification codes, or to generate reports on website data, etc. . To process images in PHP, you can use the GD library. The GD library initially supported GIF. However, because GIF used the copyright-controversial LZW algorithm, it would cause legal issues, so all GIF support has been moved from GD library version 1.6 onwards. Except, but it was added back in GD library version 2.0.28. If you use a version of the GD library between the two, the GIF relatedfunctionsare not available. This article mainly introduces the sample code for generating high-quality thumbnail images in PHP using the GD library

The following is the PHP source code (ResizeImage.php).

 $maxwidth) || ($maxheight && $height > $maxheight)){ if($maxwidth && $width > $maxwidth){ $widthratio = $maxwidth/$width; $RESIZEWIDTH=true; } if($maxheight && $height > $maxheight){ $heightratio = $maxheight/$height; $RESIZEHEIGHT=true; } if($RESIZEWIDTH && $RESIZEHEIGHT){ if($widthratio < $heightratio){ $ratio = $widthratio; }else{ $ratio = $heightratio; } }elseif($RESIZEWIDTH){ $ratio = $widthratio; }elseif($RESIZEHEIGHT){ $ratio = $heightratio; } $newwidth = $width * $ratio; $newheight = $height * $ratio; if(function_exists("imagecopyresampled")){ $newim = imagecreatetruecolor($newwidth, $newheight); imagecopyresampled($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height); }else{ $newim = imagecreate($newwidth, $newheight); imagecopyresized($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height); } ImageJpeg ($newim,$name . ".jpg"); ImageDestroy ($newim); }else{ ImageJpeg ($im,$name . ".jpg"); } } if($_FILES['image']['size']){ if($_FILES['image']['type'] == "image/pjpeg"){ $im = imagecreatefromjpeg($_FILES['image']['tmp_name']); }elseif($_FILES['image']['type'] == "image/x-png"){ $im = imagecreatefrompng($_FILES['image']['tmp_name']); }elseif($_FILES['image']['type'] == "image/gif"){ $im = imagecreatefromgif($_FILES['image']['tmp_name']); } if($im){ if(file_exists("$FILENAME.jpg")){ unlink("$FILENAME.jpg"); } ResizeImage($im,$RESIZEWIDTH,$RESIZEHEIGHT,$FILENAME); ImageDestroy ($im); } } ?>

The following is the test code (demo.php)The code is as follows:

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