Add-Type -AssemblyName System.Web;
$url='https://aip.baidubce.com/rest/2.0/ocr/v1/general_basic';
$pic='C:\1.png';
$imagedata=[Web.HttpUtility]::UrlEncode([Convert]::ToBase64String([IO.File]::ReadAllBytes($pic)));
$poststr=@(
    'access_token=24.b305c9822131e65eda05e29c157dd719.2592000.1559103982.282335-16139329',
    $('image='+$imagedata),
    'language_type=CHN_ENG',
    'detect_direction=false',
    'detect_language=false',
    'probability=false'
) -join '&';
$web=New-Object System.Net.WebClient;
$web.Headers.Add('Content-Type', 'application/x-www-form-urlencoded');
[byte[]]$postdata=[Text.Encoding]::UTF8.GetBytes($poststr);
[byte[]]$responsedata=$web.UploadData($url, 'POST', $postdata);
[Text.Encoding]::UTF8.GetString($responsedata);