Limiting Output Image Size

Last updated: 2021-10-22 14:17:36

    Overview

    COS uses the imageMogr2/size-limit API provided by CI to limit the size of an image processed (e.g., scaled or compressed).

    Restrictions

    • Format: Currently, JPG, BMP, GIF, PNG, and WebP images can be processed, and HEIF images can be decoded and processed.
    • Size: The 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, the total number of pixels (Width x Height x Number of frames) cannot exceed 250 million pixels.
    • Number of frames (for animated images): For GIF, the number of frames cannot exceed 300.

    API Format

    download_url?imageMogr2/size-limit
    

    Parameters

    Operation: size-limit

    Parameter Description
    download_url URL of the input image, formatted as &dxlt;BucketName-APPID>.cos.&dxlt;Region>.myqcloud.com/&dxlt;picture name>
    Example: examplebucket-1250000000.cos.ap-shanghai.myqcloud.com/picture.jpeg
    size-limit Limits the size of an output image. The unit can be k (KB) or m (MB).
    1. Only JPG images are supported.
    2. Appending an exclamation mark (!) means to compare the sizes of the input and output images. If the output image is smaller than the input image, the output image will be returned. Otherwise, the input image will be returned. Example: examplebucket-1250000000.cos.ap-shanghai.myqcloud.com/picture.jpg?imageMogr2/size-limit/15k!
    3. You are advised to use this parameter together with strip to remove redundant image metadata. Example: examplebucket-1250000000.cos.ap-shanghai.myqcloud.com/picture.jpg?imageMogr2/strip/format/png/size-limit/15k!
    /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

    Example 1: converting image format and limiting the output image size

    This example converts a JPG image into PNG format and limits the output image size to 15 KB:

    http://examples-1251000004.cos.ap-shanghai.myqcloud.com/sample.jpeg?imageMogr2/strip/format/png/size-limit/15k!
    

    Example 2: converting image format and limiting the output image size 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/strip/format/png/size-limit/15k!
    
    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