Text Watermarking

Last updated: 2021-10-22 14:17:34

    Overview

    COS uses the watermark API provided by CI to add text watermarks in real time. 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.

    Note:

    Image processing is charged by CI. For detailed pricing, please see the image processing prices of CI.

    An image can be processed:

    • Upon download
    • Upon upload
    • In cloud

    API Format

    1. Processing upon download

    download_url?watermark/2/text/<encodedText>
                          /font/<encodedFont>
                          /fontsize/<fontSize>
                          /fill/<encodedColor>
                          /dissolve/<dissolve>
                          /gravity/<gravity>
                          /dx/<dx>
                          /dy/<dy>
                          /batch/<type>
                          /degree/<degree>
                          /shadow/<shadow>
    
    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/2/text/<encodedText>
                          /font/<encodedFont>
                          /fontsize/<fontSize>
                          /fill/<encodedColor>
                          /dissolve/<dissolve>
                          /gravity/<gravity>
                          /dx/<dx>
                          /dy/<dy>
                          /batch/<type>
                          /degree/<degree>
                          /shadow/<shadow>"
    }]
    }
    

    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/2/text/<encodedText>
                          /font/<encodedFont>
                          /fontsize/<fontSize>
                          /fill/<encodedColor>
                          /dissolve/<dissolve>
                          /gravity/<gravity>
                          /dx/<dx>
                          /dy/<dy>
                          /batch/<type>
                          /degree/<degree>
                          /shadow/<shadow>"
    }]
    }
    
    Note:

    Authorization: Auth String (For more information, please see Request Signature.)

    Parameters

    In the code above, watermark is the operation name and the number 2 indicates that the watermark is a text.

    Parameter Description
    download_url URL of the input image, formatted as &amp;dxlt;BucketName-APPID>.cos.&amp;dxlt;Region>.myqcloud.com/&amp;dxlt;picture name>
    Example: examplebucket-1250000000.cos.ap-shanghai.myqcloud.com/picture.jpeg
    /text/ Watermark text, which must be URL-safe Base64-encoded
    /font/ Font of the text, which must be URL-safe Base64-encoded. Default font: Tahoma.ttf (see supported fonts.)
    /fontsize/ Font size, in pt. Default value: 13
    /fill/ Font color. The value must be in hexadecimal format, for example, #FF0000. For format conversion, please see RGB Color Codes Chart. The value must be URL-safe Base64-encoded. Default value: #3D3D3D (gray)
    /dissolve/ Text opacity. Value range: 1−100. Default value: 90 (meaning 90% opacity)
    /gravity/ Position of the text 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
    /batch/ Whether to tile the text watermark. If this parameter is set to 1, the text watermark will be tiled across the input image.
    /degree/ Angle to rotate text watermarks. This parameter is valid only when /batch/ is set to 1. Value range: 0−360. Default value: 0
    /shadow/ Text shadow effect. Value range: 0−100. Default value: 0, indicating no shadow.

    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 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

    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.

    Example 1: adding a text watermark

    http://examples-1251000004.cos.ap-shanghai.myqcloud.com/sample.jpeg?watermark/2/text/6IW-6K6v5LqRwrfkuIfosaHkvJjlm74/fill/IzNEM0QzRA/fontsize/20/dissolve/50/gravity/northeast/dx/20/dy/20/batch/1/degree/45
    

    After text watermarks are added:

    Example 2: adding a text 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/2/text/6IW-6K6v5LqRwrfkuIfosaHkvJjlm74/fill/IzNEM0QzRA/fontsize/20/dissolve/50/gravity/northeast/dx/20/dy/20/batch/1/degree/45
    
    Note:

    You can obtain the value of <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, please see Request Signature.

    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