You can specify Image Processing (IMG) parameters in GetObject requests to process image objects that are stored in Object Storage Service (OSS). For example, you can add image watermarks to images or convert image formats.

IMG parameters

OSS allows you to use one or more parameters to process images. You can also specify multiple IMG parameters in a style to process images at a time. For more information about image styles, see Image styles.

If you specify multiple IMG parameters, OSS processes the image in the order in which the parameters are specified. The following table describes IMG parameters.

IMG operation Parameter Description
Resize images resize Resizes images.
Add watermarks watermark Adds image watermarks or text watermarks to images.
Custom crop crop Crops rectangular images based on the specified size.
Adjust image quality quality Adjusts the quality of images in the JPG format and WebP format.
Format conversion format Converts images to specified formats.
Query the EXIF data of an image info Obtains image information, including basic information and Exchangeable Image File Format (EXIF) information.
Auto-rotate auto-orient Auto-rotates images for which the auto-orient parameter is configured.
Circle crop circle Crops images into circles of the specified size based on the center point of images.
Indexed cut indexcrop Crops images along the specified horizontal axis or vertical axis and selects one of the images.
Rounded rectangle rounded-corners Crops images into rounded rectangles based on the specified rounded corner size.
Blur blur Blurs images.
Rotate rotate Rotates images clockwise based on the specified angle.
Gradual display interlace Configures gradual display for JPG images.
Query the average tone average-hue Queries the dominant color of images.
Brightness bright Adjusts the brightness of images.
Sharpen sharpen Sharpens images.
Contrast contrast Adjusts the contrast of images.
For example, if you add the resize and quality parameters to process the example.jpg image, the URL of the image in the request is,w_300/quality,q_90. You can configure CDN back-to-origin rules to filter or retain the IMG parameters contained in the URLs of images that you want to retrieve. This way, you can retrieve source images or images that are processed by using IMG parameters.
  • Retrieve source images

    You can enable the parameter filtering feature of CDN to filter out all parameters that follow the question mark (?) in the URL of the image that you want to retrieve. In this example, the example.jpg source image is retrieved.

  • Retrieve processed images

    You can enable the parameter retaining feature of CDN to retain all parameters that follow the question mark (?) in the URL of the image that you want to retrieve. In this example, the processed image is retrieved.

For more information about how to configure CDN back-to-origin rules, see Ignore parameters.

IMG methods

You can use object URLs, API operations, and SDKs to process images. For more information, see IMG implementation modes.


When you use IMG, take note of the following items:
  • Limits on source images
    • Only JPG, PNG, BMP, GIF, WebP, and TIFF images are supported.
    • The source image cannot exceed 20 MB in size.
    • For the rotate operation, the height or width of the source image cannot exceed 4,096 pixels. For other operations, the width or height of the source image cannot exceed 30,000 pixels, and the total pixel number of the source image cannot exceed 250 million.

      The total pixel number of a dynamic image, such as a GIF image, is calculated based on the following formula: Width × Height × Number of image frames. The total pixel number of a static image, such as a PNG image, is calculated based on the following formula: Width × Height.

  • Limits on dynamic images

    You can resize, crop, rotate, and add image watermarks to only dynamic images, such as GIF images.

    To encode and decode dynamic images in the WebP format, submit a ticket.

  • Limits on resized images

    The width or height of a resized image cannot exceed 16,384 pixels. The total pixel number of the resized image cannot exceed 16,777,216.

  • Limits on image styles

    You can create up to 50 image styles for each bucket. To create more than 50 styles for a bucket, submit a ticket.


You are charged the following fees when you use IMG:
  • API operation calling fees

    A GetObject request is generated each time you use IMG to process an image. You are charged based on the number of generated requests. For more information about API operation calling fees, see API operation calling fees.

  • Traffic fees

    You are charged for the outbound traffic over the Internet based on the size of the processed images. For more information about traffic fees, see Traffic fees.

Release notes

IMG provides two versions of API operations. This topic describes the API operations of the new version. The API operations of the previous version are not updated. For more information about the compatibility between the new version and the previous version of API operations, see FAQ on using old and new versions of APIs and domain names.