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。