Quality adjustment compresses an image while retaining its original format. You can use quality adjustment parameters to modify the quality of source images stored in OSS. This topic describes the parameters and provides examples for image quality adjustment.
Quality adjustment does not work on images in lossless compression formats, such as PNG.
Parameters
Action: quality
The following are the metric descriptions:
Parameter | Description | Valid values |
q | Sets the relative quality of the image. This compresses the source image by a percentage. For example, if the source image quality is 100%, adding the Note The q parameter sets the relative quality for JPG images only. For WebP images, this parameter works the same as the Q parameter and sets the absolute quality. | [1,100] |
Q | Sets the absolute quality of the image.
| [1,100] |
Methods
Adjust the quality of a public-read or public-read-write image
You can add image processing parameters to the URL of a public-read or public-read-write image to adjust its quality.
The example in this topic uses the oss-console-img-demo-cn-hangzhou bucket in the Hangzhou region. The public endpoint for images is:
Adjust the relative quality of the image
Set the relative quality of the image to 80%: quality,q_80. The URL to process the image is: https://oss-console-img-demo-cn-hangzhou.oss-cn-hangzhou.aliyuncs.com/example.jpg?x-oss-process=image/quality,q_80
Adjust the absolute quality of the image
Set the absolute quality of the image to 90%: quality,Q_90. The URL to process the image is: https://oss-console-img-demo-cn-hangzhou.oss-cn-hangzhou.aliyuncs.com/example.jpg?x-oss-process=image/quality,Q_90
Adjust the quality of a private image
You can use Alibaba Cloud SDKs and REST APIs to adjust the quality of private images.
Use Alibaba Cloud SDKs
The following code provides examples of how to adjust the quality of a private image using Alibaba Cloud SDKs for common programming languages. For more information about how to use other SDKs, see Overview.
Java
Java SDK 3.17.4 or later is required.
import com.aliyun.oss.*;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.common.comm.SignVersion;
import com.aliyun.oss.model.GetObjectRequest;
import java.io.File;
public class Demo {
public static void main(String[] args) throws Throwable {
// The China (Hangzhou) endpoint is used as an example. Specify the actual endpoint.
String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
// Specify the region that corresponds to the endpoint, for example, cn-hangzhou.
String region = "cn-hangzhou";
// Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured.
EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
// Specify the bucket name, for example, examplebucket.
String bucketName = "examplebucket";
// Specify the full path of the object. The full path cannot include the bucket name.
String objectName = "example.jpg";
// Specify the full path of the local file, for example, D:\\dest.jpg. If the specified local file exists, it is overwritten. Otherwise, a new file is created.
String pathName = "D:\\dest.jpg";
// Create an OSSClient instance.
// When the OSSClient instance is no longer needed, call the shutdown method to release resources.
ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);
OSS ossClient = OSSClientBuilder.create()
.endpoint(endpoint)
.credentialsProvider(credentialsProvider)
.clientConfiguration(clientBuilderConfiguration)
.region(region)
.build();
try {
// Set the absolute quality of the source image to 80%.
String image = "image/quality,Q_80";
GetObjectRequest request = new GetObjectRequest(bucketName, objectName);
request.setProcess(image);
// Name the processed image dest.jpg and save it to a local path.
// If you specify only the filename, such as dest.jpg, without a full path, the file is saved to the local path of the project by default.
ossClient.getObject(request, new File("D:\\dest.jpg"));
} catch (OSSException oe) {
System.out.println("Caught an OSSException, which means your request made it to OSS, "
+ "but was rejected with an error response for some reason.");
System.out.println("Error Message:" + oe.getErrorMessage());
System.out.println("Error Code:" + oe.getErrorCode());
System.out.println("Request ID:" + oe.getRequestId());
System.out.println("Host ID:" + oe.getHostId());
} catch (ClientException ce) {
System.out.println("Caught an ClientException, which means the client encountered "
+ "a serious internal problem while trying to communicate with OSS, "
+ "such as not being able to access the network.");
System.out.println("Error Message:" + ce.getMessage());
} finally {
if (ossClient != null) {
ossClient.shutdown();
}
}
}
}PHP
PHP SDK 2.7.0 or later is required.
<?php
if (is_file(__DIR__ . '/../autoload.php')) {
require_once __DIR__ . '/../autoload.php';
}
if (is_file(__DIR__ . '/../vendor/autoload.php')) {
require_once __DIR__ . '/../vendor/autoload.php';
}
use OSS\Credentials\EnvironmentVariableCredentialsProvider;
use OSS\OssClient;
// Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured.
$provider = new EnvironmentVariableCredentialsProvider();
// Set yourEndpoint to the endpoint of the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com.
$endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
// Specify the bucket name, for example, examplebucket.
$bucket= "examplebucket";
// Specify the full path of the object, for example, exampledir/exampleobject.jpg. The full path cannot include the bucket name.
$object = "src.jpg";
// Specify the full path of the local file, for example, D:\\dest.jpg. If the specified local file exists, it is overwritten. Otherwise, a new file is created.
// If you specify only the filename, such as dest.jpg, without a full path, the file is saved to the local path of the project by default.
$download_file = "D:\\dest.jpg";
$config = array(
"provider" => $provider,
"endpoint" => $endpoint,
"signatureVersion" => OssClient::OSS_SIGNATURE_VERSION_V4,
// Specify the general-purpose region ID of Alibaba Cloud.
"region" => "cn-hangzhou"
);
$ossClient = new OssClient($config);
// Set the absolute quality of the source image to 80%.
$image = "image/quality,Q_80";
$options = array(
OssClient::OSS_FILE_DOWNLOAD => $download_file,
OssClient::OSS_PROCESS => $image);
// Save the processed image to a local path.
$ossClient->getObject($bucket, $object, $options); Python
Python SDK 2.18.4 or later is required.
# -*- coding: utf-8 -*-
import oss2
from oss2.credentials import EnvironmentVariableCredentialsProvider
# Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured.
auth = oss2.ProviderAuthV4(EnvironmentVariableCredentialsProvider())
# Set yourEndpoint to the endpoint of the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com.
## Set the endpoint of the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com.
endpoint = 'https://oss-cn-hangzhou.aliyuncs.com'
# Specify the general-purpose region ID of Alibaba Cloud.
region = 'cn-hangzhou'
bucket = oss2.Bucket(auth, endpoint, 'examplebucket', region=region)
# Specify the name of the source image. If the image is not in the root directory of the bucket, specify the full path, for example, exampledir/example.jpg.
key = 'src.jpg'
# Specify the name of the processed image.
new_pic = 'D:\\dest.jpg'
# Set the absolute quality of the source image to 80%.
image = 'image/quality,Q_80'
bucket.get_object_to_file(key, new_pic, process=image)Go
Go SDK 3.0.2 or later is required.
package main
import (
"fmt"
"os"
"github.com/aliyun/aliyun-oss-go-sdk/oss"
)
func HandleError(err error) {
fmt.Println("Error:", err)
os.Exit(-1)
}
func main() {
// Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured.
provider, err := oss.NewEnvironmentVariableCredentialsProvider()
if err != nil {
fmt.Println("Error:", err)
os.Exit(-1)
}
// Create an OSSClient instance.
// Set yourEndpoint to the endpoint of the bucket. The China (Hangzhou) endpoint is used as an example. Set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. Specify the actual endpoint for other regions.
client, err := oss.New("https://oss-cn-hangzhou.aliyuncs.com", "", "", oss.SetCredentialsProvider(&provider), oss.AuthVersion(oss.AuthV4), oss.Region("cn-hangzhou"))
if err != nil {
HandleError(err)
}
// Specify the name of the bucket where the source image is stored, for example, examplebucket.
bucketName := "examplebucket"
bucket, err := client.Bucket(bucketName)
if err != nil {
HandleError(err)
}
// Specify the name of the source image. If the image is not in the root directory of the bucket, specify the full path, for example, exampledir/example.jpg.
sourceImageName := "src.jpg"
// Specify the name of the processed image.
targetImageName := "D://dest.jpg"
// Set the absolute quality of the source image to 80%.
image := "image/quality,Q_80"
err = bucket.GetObjectToFile(sourceImageName, targetImageName, oss.Process(image))
if err != nil {
HandleError(err)
}
}Use the REST API
If your program has high customization requirements, you can directly make REST API requests. To make REST API requests, you must manually write code to calculate the signature. For more information, see Signature V4 (recommended).
You can process images by adding quality adjustment parameters to a GetObject request.
GET /oss.jpg?x-oss-process=image/quality,Q_80 HTTP/1.1
Host: oss-example.oss-cn-hangzhou.aliyuncs.com
Date: Fri, 28 Oct 2022 06:40:10 GMT
Authorization: OSS4-HMAC-SHA256 Credential=LTAI********************/20250417/cn-hangzhou/oss/aliyun_v4_request,Signature=a7c3554c729d71929e0b84489addee6b2e8d5cb48595adfc51868c299c0c218e