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Image Watermark

Last updated: 2022-10-19 12:15:46

    Feature Overview

    COS implements image watermarking through the watermark API provided by CI; therefore, only images stored in CI-bound buckets can be processed. For the restrictions on basic image processing (including watermarking), see Specifications and Limits.

    An image can be processed:

    • During download
    • During upload
    • In the cloud
    Note:

    • Image processing is charged by CI. For detailed pricing, see Image Processing Fees.
    • Up to ten image watermarks can be added to an image.
    • Animated images cannot be used as watermarks.

    API Sample

    1. Processing during download

    GET /<ObjectKey>?watermark/1/image/<encodedURL>
                          /gravity/<gravity>
                          /dx/<dx>
                          /dy/<dy>
                          /blogo/<type> HTTP/1.1
    Host: <BucketName-APPID>.cos.<Region>.myqcloud.com
    Date: <GMT Date>
    Authorization: <Auth String>
    
    Note:

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

    2. Processing during 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>"
    }]
    }
    
    Note:

    Pic-Operations is a JSON string. Its parameters are as described in Persistent Image Processing.

    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:

    Parameters

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

    Parameter Description
    ObjectKey Object name, such as folder/sample.jpg.
    /image/ Image watermark URL, which must be URL-safe Base64-encoded. 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 px. Default value: 0.
    /dy/ Vertical offset in px. 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). Valid values:
  • 1: Scales by width.
  • 2: Scales by height.
  • 3: Scales by area.
  • /spcent/ Scale ratio of the image watermark in permillage. This parameter must be used together with /scatype/. Value range:
  • 1−1000 (if /scatype/ is set to 1)
  • 1−1000 (if /scatype/ is set to 2)
  • 1−250 (if /scatype/ is set to 3)
    Example: http://examples-1251000004.cos.ap-shanghai.myqcloud.com/sample.jpeg?watermark/1/image/xxxxxxx/scatype/3/spcent/250
  • /dissolve/ Image watermark opacity. Value range: 1−100. Default value: 90 (meaning 90% opacity).
    /batch/ Whether to tile the image watermark. If this parameter is set to 1, the image watermark will be tiled across the input image.
    /degree/ Angle to rotate the image watermark. This parameter will take effect only when /batch/ is set to 1. Value range: 0−360. Default value: 0.
    Note:

    An image watermark must:

    • Be stored in the same bucket as the input image.
    • Be accessible at a URL containing a COS domain name (CDN acceleration domain names such as examplebucket-1250000000.file.myqcloud.com/shuiyin_2.png are not supported). If the image watermark is set to privately readable, the URL 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 for an operation, the corresponding red dot becomes the reference point, 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.
    • If gravity is set to west or east, dy is invalid.

    Samples

    Note:

    Processing during 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, see Persistent Image Processing and use the processing during upload or processing in-cloud data feature.

    Sample 1: Adding an image watermark

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

    The effect of an added image watermark is as follows:

    Sample 2: Adding an image watermark with the tile mode and opacity specified

    https://examples-1251000004.cos.ap-shanghai.myqcloud.com/sample.jpeg?watermark/1/image/aHR0cDovL2V4YW1wbGVzLTEyNTEwMDAwMDQucGljc2gubXlxY2xvdWQuY29tL3NodWl5aW4uanBn/gravity/southeast/batch/1/degree/45/dissolve/40/
    

    The effect of an added image watermark rotated by 45 degrees and tiled with 40% opacity is as follows:

    Sample 3: 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 carried. The signature is concatenated with other processing parameters by 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 get the value of <signature> as instructed in Request Signature.

    Notes

    To prevent unauthorized users from accessing or downloading the input image by using a URL that does not contain any processing parameter, you can add the processing parameters to the request signature, making the processing parameters the key of the parameter with the value left empty. The following is a simple sample for your reference (it might have expired or become inaccessible). For more information, see Upload via Pre-Signed URL.

    http://examples-1251000004.cos.ap-shanghai.myqcloud.com/sample.jpeg?q-sign-algorithm=sha1&q-ak=AKID********************&q-sign-time=1593342360;1593342720&q-key-time=1593342360;1593342720&q-header-list=&q-url-param-list=watermark%252f1%252fimage%252fahr0cdovl2v4yw1wbgvzlteyntewmdawmdqucgljc2gubxlxy2xvdwquy29tl3nodwl5aw4uanbn%252fgravity%252fsoutheast&q-signature=26a429871963375c88081ef60247c5746e834a98&watermark/1/image/aHR0cDovL2V4YW1wbGVzLTEyNTEwMDAwMDQucGljc2gubXlxY2xvdWQuY29tL3NodWl5aW4uanBn/gravity/southeast
    
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