Image Watermarking

Last updated: 2021-07-30 11:25:47

    Overview

    COS implements Image Watermarking using the watermark API provided by Cloud Infinite (CI) and thus only images stored in CI-bound buckets can be processed. For the restrictions on Basic Image Processing (including watermarking), please see Rules and Limits.

    An image can be processed:

    • Upon download
    • Upon upload
    • In cloud
    Note:

    • Image Processing is charged by CI. For detailed pricing, please see Basic image processing fee in Billing and Pricing.
    • You can overlay up to 10 image watermarks over a single image.
    • An animated image cannot be used as a watermark.

    API Format

    1. Processing upon download

    download_url?watermark/1/image/<encodedURL>
                          /gravity/<gravity>
                          /dx/<dx>
                          /dy/<dy>
                          /blogo/<type>
    
    Note:

    Spaces and line breaks above are for readability only and can be ignored.

    2. Processing upon upload

    PUT /<ObjectKey> HTTP/1.1
    Host: <BucketName-APPID>.cos.<Region>.myqcloud.com
    Date: GMT Date
    Authorization: Auth String
    Pic-Operations: 
    {
    "is_pic_info": 1,
    "rules": [{
        "fileid": "exampleobject",
        "rule": "watermark/1/image/<encodedURL>
                          /gravity/<gravity>
                          /dx/<dx>
                          /dy/<dy>
                          /blogo/<type>"
    }]
    }
    

    3. Processing in-cloud data

    POST /<ObjectKey>?image_process HTTP/1.1
    Host: <BucketName-APPID>.cos.<Region>.myqcloud.com
    Date: GMT Date
    Content-length: Size
    Authorization: Auth String
    Pic-Operations: 
    {
    "is_pic_info": 1,
    "rules": [{
        "fileid": "exampleobject",
        "rule": "watermark/1/image/<encodedURL>
                          /gravity/<gravity>
                          /dx/<dx>
                          /dy/<dy>
                          /blogo/<type>"
    }]
    }
    
    Note:

    Processing upon download is used as an example here, which does not store the output image in a bucket. If you need to store the output image, please see Persistent Image Processing and use Processing upon upload or Processing in-cloud data.

    Parameters

    In the code above, watermark is the operation name and the number 1 indicates that the watermark is an image.

    Parameter Description
    download_url URL of the input image, formatted as <bucketname-appid>.cos.<region>.myqcloud.com/<picture name="">
    Example: examplebucket-1250000000.cos.ap-shanghai.myqcloud.com/picture.jpeg
    /image/ URL-safe Base64-encoded URL of the image watermark. For example, if the image watermark URL is http://examplebucket-1250000000.cos.ap-shanghai.myqcloud.com/shuiyin_2.png, you should set this parameter to aHR0cDovL2V4YW1wbGVidWNrZXQtMTI1MDAwMDAwMC5jb3MuYXAtc2hhbmdoYWkubXlxY2xvdWQuY29tL3NodWl5aW5fMi5wbmc.
    /gravity/ Position of the image watermark, which is a square in a 3x3 grid. Default value: southeast
    /dx/ Horizontal offset in pixels. Default value: 0
    /dy/ Vertical offset in pixels. Default value: 0
    /blogo/ Adaptation mode for an image watermark that is larger than the input image. Valid values:
  • 1: scales the image watermark to the size of the input image.
  • 2: crops the image watermark to the size of the input image.
  • /scatype/ Scaling mode for the image watermark (relative to the input image). This parameter must be used together with /spcent/. Valid values:
  • 1: scales by width.
  • 2: scales by height.
  • 3: scales by area.
  • /spcent/ Scale ratio of the image watermark (relative to the input image), in permillage. This parameter must be used together with /scatype/. Value range: [1,1000]. By default, the image watermark is not scaled.
    Note:

    An image watermark must:

    • Be stored in the same bucket as the input image.
    • Have a URL containing a COS domain name (a CDN acceleration domain name such as examplebucket-1250000000.file.myqcloud.com/shuiyin_2.png is unsupported) and be accessible (if the image watermark is set to private-read, it must carry a signature).
    • Have a URL starting with http://. Note that “http://” cannot be omitted or changed to “https://”. For example, examplebucket-1250000000.cos.ap-shanghai.myqcloud.com/shuiyin_2.png and https://examplebucket-1250000000.cos.ap-shanghai.myqcloud.com/shuiyin_2.png are invalid watermark URLs.

    3x3 Grid Position Diagram

    The 3x3 grid position diagram is as follows. Once you specify the gravity parameter to position your watermark, the corresponding red dot becomes the reference point of the square, and offsets will be relative to this point.

    Note:

    • If gravity is set to center, dx and dy are invalid.
    • If gravity is set to north or south, dx is invalid and the watermark will be centered horizontally.
    • If gravity is set to west or east, dy is invalid and the watermark will be centered vertically.

    Examples

    Adding an image watermark

    http://examples-1251000004.cos.ap-shanghai.myqcloud.com/sample.jpeg?watermark/1/image/aHR0cDovL2V4YW1wbGVzLTEyNTEwMDAwMDQucGljc2gubXlxY2xvdWQuY29tL3NodWl5aW4uanBn/gravity/southeast
    

    After an image watermark is added:

    Adding an image watermark with a signature carried

    This example processes the image in the same way as in the example above except that a signature is added. The signature is joined with other processing parameters using an ampersand (&):

    http://examples-1251000004.cos.ap-shanghai.myqcloud.com/sample.jpeg?q-sign-algorithm=<signature>&watermark/1/image/aHR0cDovL2V4YW1wbGVzLTEyNTEwMDAwMDQucGljc2gubXlxY2xvdWQuY29tL3NodWl5aW4uanBn/gravity/southeast
    
    Note:

    You can obtain the value of <signature> by referring to Request Signature.