<?php
/**
* 裁切图片 高度冲裁
 * @param unknown $src_file   源文件
 * @param unknown $dst_file   新文件名
 * @param number $height      裁切掉的高度
*/
function my_image_resize($src_file, $dst_file, $height = 30) {
    if (! file_exists ( $src_file )) {
        echo $src_file . " is not exists !";
        exit ();
    }
    $type = exif_imagetype ( $src_file );
    $support_type = array (
            IMAGETYPE_JPEG,
            IMAGETYPE_PNG,
            IMAGETYPE_GIF
    );
    if (! in_array ( $type, $support_type, true )) {
        echo "this type of image does not support! only support jpg , gif or png";
        exit ();
    }
    switch ($type) {
        case IMAGETYPE_JPEG :
            $src_img = imagecreatefromjpeg ( $src_file );
            break;
        case IMAGETYPE_PNG :
            $src_img = imagecreatefrompng ( $src_file );
            break;
        case IMAGETYPE_GIF :
            $src_img = imagecreatefromgif ( $src_file );
            break;
        default :
            echo "Load image error!";
            exit ();
    }
    $w = imagesx ( $src_img );
    $h = imagesy ( $src_img );
    $ratio_w = $w;
    $ratio_h = $h - $height;
  
    $inter_img = imagecreatetruecolor ( $w, $h );
  
    imagecopyresampled ( $inter_img, $src_img, 0, 0, 0, 0, $w, $h, $w, $h );
    $new_img = imagecreatetruecolor ( $ratio_w, $ratio_h );
    imagecopy ( $new_img, $inter_img, 0, 0, 0, 0, $ratio_w, $ratio_h );
    switch ($type) {
        case IMAGETYPE_JPEG :
            imagejpeg ( $new_img, $dst_file, 100 );
            break;
        case IMAGETYPE_PNG :
            imagepng ( $new_img, $dst_file, 100 );
            break;
        case IMAGETYPE_GIF :
            imagegif ( $new_img, $dst_file, 100 );
            break;
        default :
            break;
    }
}