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Image Watermarking

Last updated: 2024-02-18 10:36:35

    Feature Overview

    CI uses the watermark API to add image watermarks. Currently, only image watermarks stored in CI can be added. An input image cannot be larger than 32 MB, with its width and height not exceeding 30,000 pixels and the total number of pixels not exceeding 250 million. The width and height of the output image cannot exceed 9,999 pixels. For an input animated image, its total number of pixels (Width x Height x Number of frames) cannot exceed 250 million.
    An image can be processed:
    Upon download
    Upon upload
    In cloud
    Note:
    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

    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 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>"
      }]
    }
    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:
    Authorization: Auth String (See Request Signature for details.)
    When this feature is used by a sub-account, relevant permissions must be granted as instructed in Authorization Granularity Details.

    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/
    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, 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/
    Opacity of the image watermark. 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 is valid 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.
    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 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.

    Examples

    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, see Persistent Image Processing and use Processing upon upload or Processing in-cloud data.

    Example 1: 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:
    
    

    Example 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:
    
    

    Example 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 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 &lt;signature> by referring to 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 example 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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