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Vehicle License Plate Recognition
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Last updated: 2025-11-19 18:34:10
Vehicle License Plate Recognition
Last updated: 2025-11-19 18:34:10
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Feature Description

The vehicle license plate detection feature uses a synchronous request method. You can use this interface to detect vehicles in images and identify information such as the vehicle's brand, color, position, and license plate location.
Note:
This interface is a GET request, uses a synchronous request method, and requires carrying a signature. For specific signature settings, please see Request Signature.
Unsupported for processing images of archive storage type and deep archive storage type on COS. If you need to process such images, please first restore archived file.

Authorization Description

When used by a sub-account, the ci:CreateLicensePlateJob permission is required. For details, see Cloud Infinite action.

Service Activation

Using this feature requires enabling Cloud Infinite in advance and binding a bucket. For details, see Bind bucket.
Use this feature requires enabling AI Content Recognition service in advance via console or API. For details, see Enable AI Content Recognition service.

Use Limits

When using this API, please confirm the relevant restrictions first. For details, see Usage limits.
Supported image formats: PNG, JPG, JPEG.
Image size: The downloaded image after encoding must not exceed 4MB.
Image pixels: It is advisable to be larger than 50*50 pixels; otherwise, it will affect the recognition effect.
Aspect ratio: It is advisable that the ratio of the long side to the short side is less than 5:1.

Fee Description

Successful API calls incur vehicle license plate detection fees and COS read request fees.
If the image belongs to the infrequent storage type on COS, a successful API call will incur COS infrequent data retrieval fees.


Request

Request sample:

GET /<ObjectKey>?ci-process=DetectCar HTTP/1.1
Host: <BucketName-APPID>.cos.<Region>.myqcloud.com
Date: <GMT Date>
Authorization: <Auth String>
Note:
Authorization: Auth String. For details, see Request Signature document.

Request parameters

Parameter Name
Description
Type
Required or Not
ObjectKey
object filename, for example: folder/document.jpg
String
Yes
ci-process
Cloud Infinite processing capability, vehicle identification fixed as DetectCar
String
Yes

Request header.

This API only uses common request headers. For details, see Common Request Headers documentation.

Request body.

The request does not have a request body.

Response

Response Headers

This API only returns the public response header. For details, see Common Response Headers documentation.

Response Body

The response body is returned as application/xml. An example including the complete node data is shown below:
<Response>
    <RequestId></RequestId>
    <CarTags>
        <Serial></Serial>
        <Brand></Brand>
        <Type></Type>
        <Color><Color>
        <Confidence></Confidence>
        <Year></Year>
        <CarLocation>
            <X></X>
            <Y></Y>
        </CarLocation>
        <PlateContent>
            <Plate></Plate>
            <Color></Color>
            <Type></Type>
            <PlateLocation>
                <X></X>
                <Y></Y>
            </PlateLocation>
        </PlateContent>
    </CarTags>
</Response>
The data are as follows:
Node Name (Keyword)
Parent Node
Description
Type
Response
None.
Container for saving results
Container
The content of Response
Node Name (Keyword)
Parent Node
Description
Type
RequestId
Response
Unique request ID, which is returned for each request. RequestId is required for locating a problem.
String
CarTags
Response
Result array of vehicle attribute recognition, support returning multiple vehicle information
Container
content of the CarTags node
Node Name (Keyword)
Parent Node
Description
Type
Serial
CarTags
Car series
String
Brand
CarTags
Vehicle brand
String
Type
CarTags
Vehicle type
String
Color
CarTags
Vehicle color
String
Confidence
CarTags
Confidence degree, 0 - 100
Int
Year
CarTags
Year, return 0 if the year cannot be identified
Int
CarLocation
CarTags
Coordinate information of the vehicle in the image, may return multiple coordinate points
Container
PlateContent
CarTags
license plate information, including license plate number, license plate color, and license plate location. Supports returning multiple license plates.
Container
content of the CarLocation node
Node Name (Keyword)
Parent Node
Description
Type
X
CarLocation
Horizontal coordinate x
Int
Y
CarLocation
Vertical coordinate y
Int
content of the PlateContent node
Node Name (Keyword)
Parent Node
Description
Type
Plate
PlateContent
License plate number information
String
Color
PlateContent
Color of the license plate
String
Type
PlateContent
Type of license plate, such as ordinary blue plate
String
PlateLocation
PlateContent
LocatioC of the license plate
Container
content of the PlateLocation node
Node Name (Keyword)
Parent Node
Description
Type
X
PlateLocation
X coordinates of the license plate's upper-left, upper-right, lower-left, and lower-right corners
Int
Y
PlateLocation
Y coordinates of the license plate's upper-left, upper-right, lower-left, and lower-right corners
Int

Error Codes

This request returns common error responses and error codes. For more information, see Error Codes.

Examples

Request

GET test.jpg?ci-process=DetectCar HTTP/1.1
Authorization: q-sign-algorithm=sha1&q-ak=**********************************&q-sign-time=1497530202;1497610202&q-key-time=1497530202;1497610202&q-header-list=&q-url-param-list=&q-signature=**************************************
Host: examplebucket-1250000000.cos.ap-beijing.myqcloud.com

Response

HTTP/1.1 200 OK
Content-Type: application/xml
Content-Length: 414641
Date: Thu, 15 Jun 2017 12:37:29 GMT
Server: tencent-ci
x-ci-request-id: NTk0MjdmODlfMjQ4OGY3XzYzYzhf****

<Response>
    <RequestId>NjE1MzEyMDlfOTBmYTUwNjRfNzUz****</RequestId>
    <CarTags>
        <Serial>Mercedes-Benz S-Class</Serial>
        <Brand>Mercedes-Benz</Brand>
        <Type>Sedan</Type>
        <Color>Black</Color>
        <Confidence>98</Confidence>
        <Year>0</Year>
        <CarLocation>
            <X>8</X>
            <Y>364</Y>
        </CarLocation>
        <CarLocation>
            <X>8</X>
            <Y>5</Y>
        </CarLocation>
        <CarLocation>
            <X>637</X>
            <Y>5</Y>
        </CarLocation>
        <CarLocation>
            <X>637</X>
            <Y>364</Y>
        </CarLocation>
        <PlateContent>
            <Plate>Shaanxi ASxxxL</Plate>
            <Color>Blue</Color>
            <Type>Ordinary blue plate</Type>
            <PlateLocation>
                <X>263</X>
                <Y>309</Y>
            </PlateLocation>
            <PlateLocation>
                <X>263</X>
                <Y>239</Y>
            </PlateLocation>
            <PlateLocation>
                <X>459</X>
                <Y>239</Y>
            </PlateLocation>
            <PlateLocation>
                <X>459</X>
                <Y>309</Y>
            </PlateLocation>
        </PlateContent>
    </CarTags>
    <CarTags>
        <Serial>Wuling Hongguang</Serial>
        <Brand>Wuling</Brand>
        <Type>Van</Type>
        <Color>White</Color>
        <Confidence>0</Confidence>
        <Year>0</Year>
        <CarLocation>
            <X>0</X>
            <Y>228</Y>
        </CarLocation>
        <CarLocation>
            <X>0</X>
            <Y>81</Y>
        </CarLocation>
        <CarLocation>
            <X>73</X>
            <Y>81</Y>
        </CarLocation>
        <CarLocation>
            <X>73</X>
            <Y>228</Y>
        </CarLocation>
    </CarTags>
</Response>

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