PHP实现图片裁剪与缩放的几种方法

图片裁剪缩放函数，支持方位裁剪和自定义坐标裁剪
    /**
     * 图片裁剪函数，支持指定定点裁剪和方位裁剪两种裁剪模式
     * @param   $src_file       原图片路径
     * @param      $new_width      裁剪后图片宽度（当宽度超过原图片宽度时，去原图片宽度）
     * @param      $new_height     裁剪后图片高度（当宽度超过原图片宽度时，去原图片高度）
     * @param      $type           裁剪方式，1-方位模式裁剪；0-定点模式裁剪。
     * @param      $pos            方位模式裁剪时的起始方位（当选定点模式裁剪时，此参数不起作用）
     *                                      1为顶端居左，2为顶端居中，3为顶端居右；
     *                                      4为中部居左，5为中部居中，6为中部居右；
     *                                      7为底端居左，8为底端居中，9为底端居右；
     * @param      $start_x        起始位置X （当选定方位模式裁剪时，此参数不起作用）
     * @param      $start_y        起始位置Y（当选定方位模式裁剪时，此参数不起作用）
     * @return                  裁剪图片存储路径
     */
    function thumb($src_file, $new_width, $new_height, $type = 1, $pos = 5, $start_x = 0, $start_y = 0) {
        $pathinfo = pathinfo($src_file);
        $dst_file = $pathinfo['dirname'] . '/' . $pathinfo['filename'] .'_'. $new_width . 'x' . $new_height . '.' . $pathinfo['extension'];
        if (!file_exists($dst_file)) {
            if ($new_width < 1 || $new_height < 1) {
                echo "params width or height error !";
                exit();
            }
            if (!file_exists($src_file)) {
                echo $src_file . " is not exists !";
                exit();
            }
            // 图像类型
            $img_type = exif_imagetype($src_file);
            $support_type = array(IMAGETYPE_JPEG, IMAGETYPE_PNG, IMAGETYPE_GIF);
            if (!in_array($img_type, $support_type, true)) {
                echo "只支持jpg、png、gif格式图片裁剪";
                exit();
            }
            /* 载入图像 */
            switch ($img_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 "载入图像错误!";
                exit();
            }
            /* 获取源图片的宽度和高度 */
            $src_width = imagesx($src_img);
            $src_height = imagesy($src_img);
            /* 计算剪切图片的宽度和高度 */
            $mid_width = ($src_width < $new_width) ? $src_width : $new_width;
            $mid_height = ($src_height < $new_height) ? $src_height : $new_height;
            /* 初始化源图片剪切裁剪的起始位置坐标 */
            switch ($pos * $type) {
                case 1://1为顶端居左
                    $start_x = 0;
                    $start_y = 0;
                    break;
                case 2://2为顶端居中
                    $start_x = ($src_width - $mid_width) / 2;
                    $start_y = 0;
                    break;
                case 3://3为顶端居右
                    $start_x = $src_width - $mid_width;
                    $start_y = 0;
                    break;
                case 4://4为中部居左
                    $start_x = 0;
                    $start_y = ($src_height - $mid_height) / 2;
                    break;
                case 5://5为中部居中
                    $start_x = ($src_width - $mid_width) / 2;
                    $start_y = ($src_height - $mid_height) / 2;
                    break;
                case 6://6为中部居右
                    $start_x = $src_width - $mid_width;
                    $start_y = ($src_height - $mid_height) / 2;
                    break;
                case 7://7为底端居左
                    $start_x = 0;
                    $start_y = $src_height - $mid_height;
                    break;
                case 8://8为底端居中
                    $start_x = ($src_width - $mid_width) / 2;
                    $start_y = $src_height - $mid_height;
                    break;
                case 9://9为底端居右
                    $start_x = $src_width - $mid_width;
                    $start_y = $src_height - $mid_height;
                    break;
                default://随机
                    break;
            }
            // 为剪切图像创建背景画板
            $mid_img = imagecreatetruecolor($mid_width, $mid_height);
            //拷贝剪切的图像数据到画板，生成剪切图像
            imagecopy($mid_img, $src_img, 0, 0, $start_x, $start_y, $mid_width, $mid_height);
            // 为裁剪图像创建背景画板
            $new_img = imagecreatetruecolor($new_width, $new_height);
            //拷贝剪切图像到背景画板，并按比例裁剪
            imagecopyresampled($new_img, $mid_img, 0, 0, 0, 0, $new_width, $new_height, $mid_width, $mid_height);
            /* 按格式保存为图片 */
            switch ($img_type) {
                case IMAGETYPE_JPEG :
                    imagejpeg($new_img, $dst_file, 100);
                    break;
                case IMAGETYPE_PNG :
                    imagepng($new_img, $dst_file, 9);
                    break;
                case IMAGETYPE_GIF :
                    imagegif($new_img, $dst_file, 100);
                    break;
                default:
                    break;
            }
        }
        return ltrim($dst_file, '.');
    }

list($src_w,$src_h)=getimagesize($src_img);  // 获取原图尺寸
$dst_scale = $dst_h/$dst_w; //目标图像长宽比
$src_scale = $src_h/$src_w; // 原图长宽比

if($src_scale>=$dst_scale)
{ 
 // 过高
 $w = intval($src_w);
 $h = intval($dst_scale*$w);
 $x = 0;
 $y = ($src_h - $h)/3;
}
else
{
// 过宽
 $h = intval($src_h);
 $w = intval($h/$dst_scale);
 $x = ($src_w - $w)/2;
 $y = 0;
}
// 剪裁
$source=imagecreatefromjpeg($src_img);
$croped=imagecreatetruecolor($w, $h);
imagecopy($croped,$source,0,0,$x,$y,$src_w,$src_h);
// 缩放
$scale = $dst_w/$w;
$target = imagecreatetruecolor($dst_w, $dst_h);
$final_w = intval($w*$scale);
$final_h = intval($h*$scale);
imagecopysampled($target,$croped,0,0,0,0,$final_w,$final_h,$w,$h);
// 保存
$timestamp = time();
imagejpeg($target, "$timestamp.jpg");
imagedestroy($target);
?>

$source_path string 源图路径

$target_width integer 目标图宽度

$target_height integer 目标图高度

支持图片类型: image/gif, image/jpeg, image/png.

function imagecropper($source_path, $target_width, $target_height)
{
 $source_info   = getimagesize($source_path);
 $source_width  = $source_info[0];
 $source_height = $source_info[1];
 $source_mime   = $source_info['mime'];
 $source_ratio  = $source_height / $source_width;
 $target_ratio  = $target_height / $target_width;

 // 源图过高
 if ($source_ratio > $target_ratio)
 {
  $cropped_width  = $source_width;
  $cropped_height = $source_width * $target_ratio;
  $source_x = 0;
  $source_y = ($source_height - $cropped_height) / 2;
 }
 // 源图过宽
 elseif ($source_ratio < $target_ratio)
 {
  $cropped_width  = $source_height / $target_ratio;
  $cropped_height = $source_height;
  $source_x = ($source_width - $cropped_width) / 2;
  $source_y = 0;
 }
 // 源图适中
 else
 {
  $cropped_width  = $source_width;
  $cropped_height = $source_height;
  $source_x = 0;
  $source_y = 0;
 }

 switch ($source_mime)
 {
  case 'image/gif':
   $source_image = imagecreatefromgif($source_path);
   break;

  case 'image/jpeg':
   $source_image = imagecreatefromjpeg($source_path);
   break;

  case 'image/png':
   $source_image = imagecreatefrompng($source_path);
   break;

  default:
   return false;
   break;
 }

 $target_image  = imagecreatetruecolor($target_width, $target_height);
 $cropped_image = imagecreatetruecolor($cropped_width, $cropped_height);

 // 裁剪
 imagecopy($cropped_image, $source_image, 0, 0, $source_x, $source_y, $cropped_width, $cropped_height);
 // 缩放
 imagecopyresampled($target_image, $cropped_image, 0, 0, 0, 0, $target_width, $target_height, $cropped_width, $cropped_height);

 header('Content-Type: image/jpeg');
 imagejpeg($target_image);
 imagedestroy($source_image);
 imagedestroy($target_image);
 imagedestroy($cropped_image);
}