wecenter学习笔记-上传图片并生成缩略图

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该文是wecenter学习笔记的一部分

上传图片并生成缩略图

这部分主要由两个模块合力完成

  • core_upload
  • core_image

上传图片

使用

AWS_APP::upload()->initialize(array(
    'allowed_types' => get_setting('allowed_upload_types'),
    'upload_path' => get_setting('upload_dir') . '/' . $item_type . '/' . gmdate('Ymd'),
    'is_image' => FALSE,
    'max_size' => get_setting('upload_size_limit')
));

...

AWS_APP::upload()->do_upload('qqfile');

...

if (AWS_APP::upload()->get_error())
{
    switch (AWS_APP::upload()->get_error())
    {
        default:
            H::ajax_json_output(AWS_APP::RSM(null, -1, AWS_APP::lang()->_t('错误代码: '.AWS_APP::upload()->get_error())));
        break;

        case 'upload_invalid_filetype':
            H::ajax_json_output(AWS_APP::RSM(null, -1, AWS_APP::lang()->_t('文件类型无效')));
        break;

        case 'upload_invalid_filesize':
           H::ajax_json_output(AWS_APP::RSM(null, -1, AWS_APP::lang()->_t("文件尺寸过大,最大允许尺寸为 ".get_setting('upload_size_limit')." KB")));
        break;
    }
}

if (! $upload_data = AWS_APP::upload()->data())
{
    H::ajax_json_output(AWS_APP::RSM(null, -1, AWS_APP::lang()->_t( '上传失败, 请与管理员联系' )));
}

步骤

  • 初始化(接受的文件类型、保存路径、是否必须是图片、最大文件尺寸)
  • 接受上传文件
  • 错误处理

实现

core_upload处理文件上传,涵盖了

文件存储和访问暴露

先会将文件存储到临时文件中,在完成后面的检查后再移动到目标目录

文件类型判定并只允许上传制定类型的文件(mimes)

根据上传文件的扩展名判定是否是allowed_types,
如果是图片文件,还会尝试获取图片尺寸(利用获取图片大小会解析图片头部信息的副作用)
另外还是通过函数finfo_filefile命令或者mime_content_type来分析文件的mimes type

system/core/upload.php#file_mime_type

// We'll need this to validate the MIME info string (e.g. text/plain; charset=us-ascii)
   $regexp = '/^([a-z\-]+\/[a-z0-9\-\.\+]+)(;\s.+)?$/';

  1. 优先先会尝试使用 `finfo_file`

    /* Fileinfo extension - most reliable method
     *
     * Unfortunately, prior to PHP 5.3 - it's only available as a PECL extension and the
     * more convenient FILEINFO_MIME_TYPE flag doesn't exist.
     */
    if (function_exists('finfo_file'))
    {
        $finfo = finfo_open(FILEINFO_MIME);
        if (is_resource($finfo)) // It is possible that a FALSE value is returned, if there is no magic MIME database file found on the system
        {
            $mime = @finfo_file($finfo, $file['tmp_name']);
            finfo_close($finfo);
    
            /* According to the comments section of the PHP manual page,
             * it is possible that this function returns an empty string
             * for some files (e.g. if they don't exist in the magic MIME database)
             */
            if (is_string($mime) && preg_match($regexp, $mime, $matches))
            {
                $this->file_type = $matches[1];
                return;
            }
        }
    }
    
  2. 其次是file --brief --mime命令

    /* This is an ugly hack, but UNIX-type systems provide a "native" way to detect the file type,
     * which is still more secure than depending on the value of $_FILES[$field]['type'], and as it
     * was reported in issue #750 (https://github.com/EllisLab/CodeIgniter/issues/750) - it's better
     * than mime_content_type() as well, hence the attempts to try calling the command line with
     * three different functions.
     *
     * Notes:
     *  - the DIRECTORY_SEPARATOR comparison ensures that we're not on a Windows system
     *  - many system admins would disable the exec(), shell_exec(), popen() and similar functions
     *    due to security concerns, hence the function_exists() checks
     */
    if (DIRECTORY_SEPARATOR !== '\\')
    {
        $cmd = 'file --brief --mime ' . @escapeshellarg($file['tmp_name']) . ' 2>&1';
    
        if (function_exists('exec'))
        {
            /* This might look confusing, as $mime is being populated with all of the output when set in the second parameter.
             * However, we only neeed the last line, which is the actual return value of exec(), and as such - it overwrites
             * anything that could already be set for $mime previously. This effectively makes the second parameter a dummy
             * value, which is only put to allow us to get the return status code.
             */
            $mime = @exec($cmd, $mime, $return_status);
            if ($return_status === 0 && is_string($mime) && preg_match($regexp, $mime, $matches))
            {
                $this->file_type = $matches[1];
                return;
            }
        }
    
        if ( (bool) @ini_get('safe_mode') === FALSE && function_exists('shell_exec'))
        {
            $mime = @shell_exec($cmd);
            if (strlen($mime) > 0)
            {
                $mime = explode("\n", trim($mime));
                if (preg_match($regexp, $mime[(count($mime) - 1)], $matches))
                {
                    $this->file_type = $matches[1];
                    return;
                }
            }
        }
    
        if (function_exists('popen'))
        {
            $proc = @popen($cmd, 'r');
            if (is_resource($proc))
            {
                $mime = @fread($proc, 512);
                @pclose($proc);
                if ($mime !== FALSE)
                {
                    $mime = explode("\n", trim($mime));
                    if (preg_match($regexp, $mime[(count($mime) - 1)], $matches))
                    {
                        $this->file_type = $matches[1];
                        return;
                    }
                }
            }
        }
    }
    
  3. 然后 mime_content_type

    // Fall back to the deprecated mime_content_type(), if available (still better than $_FILES[$field]['type'])
    if (function_exists('mime_content_type'))
    {
        $this->file_type = @mime_content_type($file['tmp_name']);
        if (strlen($this->file_type) > 0) // It's possible that mime_content_type() returns FALSE or an empty string
        {
            return;
        }
    }
    
  4. 最后才会考虑用 getimagesize

    if (function_exists('getimagesize'))
    {
        $imageinfo = @getimagesize($file['tmp_name']);
    
        if ($imageinfo['mime'])
        {
            $this->file_type = $imageinfo['mime'];
    
            return;
        }
    }
    
    $this->file_type = $file['type'];
    

文件大小检查

图片尺寸检查

文件名和文件内容安全校验(xss clean)

会去掉文件名中的各类非法字符

system/core/upload.php#clean_file_name

    $bad = array(
                   "<!--",
                   "-->",
                   "'",
                   "<",
                   ">",
                   '"',
                   '&',
                   '$',
                   '=',
                   ';',
                   '?',
                   '/',
                   "%20",
                   "%22",
                   "%3c",      // <
                   "%253c",    // <
                   "%3e",      // >
                   "%0e",      // >
                   "%28",      // (
                   "%29",      // )
                   "%2528",    // (
                   "%26",      // &
                   "%24",      // $
                   "%3f",      // ?
                   "%3b",      // ;
                   "%3d"       // =
               );

   $filename = str_replace($bad, '', $filename);

** 文件内容的xss clean **

system/core/upload.php#do_xss_clean

if (function_exists('memory_get_usage') && memory_get_usage() && ini_get('memory_limit') != '')
{
    $current = ini_get('memory_limit') * 1024 * 1024;

    // There was a bug/behavioural change in PHP 5.2, where numbers over one million get output
    // into scientific notation.  number_format() ensures this number is an integer
    // http://bugs.php.net/bug.php?id=43053

    $new_memory = number_format(ceil(filesize($file) + $current), 0, '.', '');

    @ini_set('memory_limit', $new_memory); // When an integer is used, the value is measured in bytes. - PHP.net
}

// If the file being uploaded is an image, then we should have no problem with XSS attacks (in theory), but
// IE can be fooled into mime-type detecting a malformed image as an html file, thus executing an XSS attack on anyone
// using IE who looks at the image.  It does this by inspecting the first 255 bytes of an image.  To get around this
// CI will itself look at the first 255 bytes of an image to determine its relative safety.  This can save a lot of
// processor power and time if it is actually a clean image, as it will be in nearly all instances _except_ an
// attempted XSS attack.

if (function_exists('getimagesize') && @getimagesize($file) !== FALSE)
{
    if (($file = @fopen($file, 'rb')) === FALSE) // "b" to force binary
    {
        return FALSE; // Couldn't open the file, return FALSE
    }

    $opening_bytes = fread($file, 256);
    fclose($file);

    // These are known to throw IE into mime-type detection chaos
    // <a, <body, <head, <html, <img, <plaintext, <pre, <script, <table, <title
    // title is basically just in SVG, but we filter it anyhow

    if ( ! preg_match('/<(a|body|head|html|img|plaintext|pre|script|table|title)[\s>]/i', $opening_bytes))
    {
        return TRUE; // its an image, no "triggers" detected in the first 256 bytes, we're good
    }
    else
    {
        return FALSE;
    }
}

if (($data = @file_get_contents($file)) === FALSE)
{
    return FALSE;
}

return $data;

处理步骤

  1. 调整内存memory_limit为读入文件保留足够的内存
  2. 如果是图片文件,要求文件不能有任何html标签(a|body|head|html|img|plaintext|pre|script|table|title
  3. 如果不是图片,只要不为空即可。

生成缩略图算法

使用

AWS_APP::image()->initialize(array(
    'quality' => 90,
    'source_image' => $upload_data['full_path'],
    'new_image' => $thumb_file[$key],
    'width' => $val['w'],
    'height' => $val['h']
))->resize();

core_image负责缩略图的生成

  • 生成指定大小的缩略图(resize)
  • 可以选择输出到文件或者浏览器

resize的算法支持缩放和裁剪,并支持压缩到一定清晰度

** 缩放 **

  • IMAGE_CORE_SC_NOT_KEEP_SCALE

    直接缩放或拉伸,不考虑比例

  • IMAGE_CORE_SC_BEST_RESIZE_WIDTH

    优先匹配缩放后的目标宽度

  • IMAGE_CORE_SC_BEST_RESIZE_HEIGHT

    高度优先匹配

** 裁剪 **

  • IMAGE_CORE_CM_DEFAULT

    不裁剪

  • IMAGE_CORE_CM_LEFT_OR_TOP

    对齐左上角,裁剪右下角

  • IMAGE_CORE_CM_MIDDLE

    居中对齐,裁剪四周

  • IMAGE_CORE_CM_RIGHT_OR_BOTTOM

    右下角对齐,裁剪左上角

实现

内部支持GDImageMagick来处理图片,支持jpg/png/gif三种格式的图片处理。

处理步骤:

  1. 根据图片的宽窄比计算目标缩放区域(优先按长边缩放)

    system/core/image.php#imageProcessImageMagick

    if ($this->source_image_w * $this->height > $this->source_image_h * $this->width)
    {
        $match_w = round($this->width * $this->source_image_h / $this->height);
        $match_h = $this->source_image_h;
    }
    else
    {
        $match_h = round($this->height * $this->source_image_w / $this->width);
        $match_w = $this->source_image_w;
    }
    
  2. 根据裁剪需求,设定目标区域

    system/core/image.php#imageProcessImageMagick

    switch ($this->clipping)
    {
        case IMAGE_CORE_CM_LEFT_OR_TOP:
            $this->source_image_x = 0;
            $this->source_image_y = 0;
        break;
    
        case IMAGE_CORE_CM_MIDDLE:
            $this->source_image_x = round(($this->source_image_w - $match_w) / 2);
            $this->source_image_y = round(($this->source_image_h - $match_h) / 2);
        break;
    
        case IMAGE_CORE_CM_RIGHT_OR_BOTTOM:
            $this->source_image_x = $this->source_image_w - $match_w;
            $this->source_image_y = $this->source_image_h - $match_h;
        break;
    }
    
    $this->source_image_w = $match_w;
    $this->source_image_h = $match_h;
    $this->source_image_x += $this->start_x;
    $this->source_image_y += $this->start_y;
    
  3. 根据缩放设置,计算出目标图片的真实尺寸

    system/core/image.php#imageProcessImageMagick

    $resize_height = $this->height;
    $resize_width = $this->width;
    
    if ($this->scale != IMAGE_CORE_SC_NOT_KEEP_SCALE)
    {
        if ($this->scale == IMAGE_CORE_SC_BEST_RESIZE_WIDTH)
        {
            $resize_height = round($this->width * $this->source_image_h / $this->source_image_w);
            $resize_width = $this->width;
        }
        else if ($this->scale == IMAGE_CORE_SC_BEST_RESIZE_HEIGHT)
        {
            $resize_width = round($this->height * $this->source_image_w / $this->source_image_h);
            $resize_height = $this->height;
        }
    }
    
  4. 按目标区域裁剪图片

  5. 缩放图片到目标尺寸

  6. 输出图片

具体到图片处理记得,根据库的不同,略有不同

** imagemagick **

$im = new Imagick();

$im->readimageblob(file_get_contents($this->source_image));

$im->setCompressionQuality($this->quality);

if ($this->source_image_x OR $this->source_image_y)
{
    $im->cropImage($this->source_image_w, $this->source_image_h, $this->source_image_x, $this->source_image_y);
}

$im->thumbnailImage($resize_width, $resize_height, true);

if ($this->option == IMAGE_CORE_OP_TO_FILE AND $this->new_image)
{
    file_put_contents($this->new_image, $im->getimageblob());
}
else if ($this->option == IMAGE_CORE_OP_OUTPUT)
{
    $output = $im->getimageblob();
            $outputtype = $im->getFormat();

    header("Content-type: $outputtype");
    echo $output;
    die;
}

** gd **

通过 imagecopyresampledimagecopyresized可以一步作为裁剪和缩放

$func_resize($dst_img, $im, $dst_x, $dst_y, $this->source_image_x, $this->source_image_y, $fdst_w, $fdst_h, $this->source_image_w, $this->source_image_h);


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