tencent cloud

Quality Change
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Last updated: 2025-07-11 16:30:28
Quality Change
Last updated: 2025-07-11 16:30:28
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Feature Overview

COS uses the imageMogr2 API provided by CI to adjust the quality of an image.
An image can be processed:
Upon download
Upon upload
In cloud
Note:
Image Processing is charged by CI. For detailed pricing, see Image Processing Fees.
This API supports images in JPG, WebP, TPG, HEIF, or AVIF format.

API Format

1. Processing upon download

GET /<ObjectKey>?imageMogr2/quality/<Quality>
                       /rquality/<quality>
                       /lquality/<quality> HTTP/1.1
Host: <BucketName-APPID>.cos.<Region>.myqcloud.com
Date: <GMT Date>
Authorization: <Auth String>

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": "imageMogr2/quality/<Quality>
                       /rquality/<quality>
                       /lquality/<quality>"
  }]
}
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": "imageMogr2/quality/<Quality>
                       /rquality/<quality>
                       /lquality/<quality>"
  }]
}
Note:
Authorization: Auth String (see Request Signature for more information)
When this feature is used by a sub-account, relevant permissions must be granted as instructed in Authorization Granularity Details.

Parameters

Operation: quality
Parameter
Description
ObjectKey
Object name, such as folder/sample.jpg.
/quality/<Quality>
Absolute quality of the image. Value range: 0−100. Default value: quality of the input image. The smaller value between the input image quality and the specified quality is used. If there is an exclamation mark (!) after <Quality> (for example, 90!), the specified quality is used.
/rquality/<quality>
Relative quality of the image, relative to that of the input image. Value range: 0−100. For example, if the input image quality is 80 and rquality is set to 80, the quality of the output image is 64 (that is, 80 x 80%).
/lquality/<quality>
The lowest quality of the output image. Value range: 0−100.
If the input image quality is 85 and lquality is set to 80, the quality of the output image is 85.
If the input image quality is 60 and lquality is set to 80, the quality of the output image will be improved to 80.
/ignore-error/1
If this parameter is carried and the image failed to be processed because it is too large, the input image will be returned with no error reported.

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: Setting absolute quality

This example sets the absolute quality to 60:
http://examples-1251000004.picsh.myqcloud.com/sample.jpeg?imageMogr2/quality/60
Output image:



Example 2: Setting relative quality

This example sets the relative quality to 60:
http://examples-1251000004.cos.ap-shanghai.myqcloud.com/sample.jpeg?imageMogr2/rquality/60
Output image:



Example 3: Setting the relative quality to 60 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>&imageMogr2/rquality/60
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 not be valid or accessible anymore). 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

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