PHP实现对png图像进行缩放的方法(支持透明背景)_php技巧

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) {
        // 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。