PHP实现对png图像进行缩放的方法(支持透明背景)

本文实例讲述了PHP实现对png图像进行缩放的方法。分享给大家供大家参考。具体实现方法如

本文实例讲述了PHP实现对png图像进行缩放的方法。分享给大家供大家参考。具体实现方法如下：

function smart_resize_image( $file, $width = 0, $height = 0, $proportional = false, $output = 'file', $delete_original = true, $use_linux_commands = false )
{
 if ( $height <= 0 && $width <= 0 ) {
 return false;
 }
 $info = getimagesize($file);
 $image = '';
 $final_width = 0;
 $final_height = 0;
 list($width_old, $height_old) = $info;
 if ($proportional) {
 if ($width == 0) $factor = $height/$height_old;
 elseif ($height == 0) $factor = $width/$width_old;
 else $factor = min ( $width / $width_old, $height / $height_old); 
 $final_width = round ($width_old * $factor);
 $final_height = round ($height_old * $factor);
 }
 else { 
 $final_width = ( $width <= 0 ) ? $width_old : $width;
 $final_height = ( $height <= 0 ) ? $height_old : $height;
 }
 switch ($info[2] ) {
 case IMAGETYPE_GIF:
 $image = imagecreatefromgif($file);
 break;
 case IMAGETYPE_JPEG:
 $image = imagecreatefromjpeg($file);
 break;
 case IMAGETYPE_PNG:
 $image = imagecreatefrompng($file);
 break;
 default:
 return false;
 }
 $image_resized = imagecreatetruecolor( $final_width, $final_height );
 if ( ($info[2] == IMAGETYPE_GIF) || ($info[2] == IMAGETYPE_PNG) ) {
 $trnprt_indx = imagecolortransparent($image);
 // If we have a specific transparent color
 if ($trnprt_indx >= 0) {
 // Get the original image's transparent color's RGB values
 $trnprt_color = imagecolorsforindex($image, $trnprt_indx);
 // Allocate the same color in the new image resource
 $trnprt_indx = imagecolorallocate($image_resized, $trnprt_color['red'], $trnprt_color['green'], $trnprt_color['blue']);
 // Completely fill the background of the new image with allocated color.
 imagefill($image_resized, 0, 0, $trnprt_indx);
 // Set the background color for new image to transparent
 imagecolortransparent($image_resized, $trnprt_indx);
 }
 // Always make a transparent background color for PNGs that don't have one allocated already
 elseif ($info[2] == IMAGETYPE_PNG) {
 // Turn off transparency blending (temporarily)
 imagealphablending($image_resized, false);
 // Create a new transparent color for image
 $color = imagecolorallocatealpha($image_resized, 0, 0, 0, 127);
 // Completely fill the background of the new image with allocated color.
 imagefill($image_resized, 0, 0, $color);
 // Restore transparency blending
 imagesavealpha($image_resized, true);
 }
 }
 imagecopyresampled($image_resized, $image, 0, 0, 0, 0, $final_width, $final_height, $width_old, $height_old);
 if ( $delete_original ) {
 if ( $use_linux_commands )
 exec('rm '.$file);
 else
 @unlink($file);
 }
 switch ( strtolower($output) ) {
 case 'browser':
 $mime = image_type_to_mime_type($info[2]);
 header("Content-type: $mime");
 $output = NULL;
 break;
 case 'file':
 $output = $file;
 break;
 case 'return':
 return $image_resized;
 break;
 default:
 break;
 }
 switch ($info[2] ) {
 case IMAGETYPE_GIF:
 imagegif($image_resized, $output);
 break;
 case IMAGETYPE_JPEG:
 imagejpeg($image_resized, $output);
 break;
 case IMAGETYPE_PNG:
 imagepng($image_resized, $output);
 break;
 default:
 return false;
 }
 return true;
}

希望本文所述对大家的php程序设计有所帮助。