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;}