Object Storage Service:Synchronous processing (Go SDK V2)

Prerequisites

Before you begin, make sure you have:

• An OSS bucket containing the object to process

• Access credentials configured as environment variables (OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET)

• The OSS Go SDK V2 installed (github.com/aliyun/alibabacloud-oss-go-sdk-v2)

Usage notes

• The examples in this document use the China (Hangzhou) region (cn-hangzhou) with a public endpoint. To access OSS from other Alibaba Cloud services in the same region, use an internal endpoint instead. See OSS regions and endpoints for the full list.

• Credentials are read from environment variables. See Configure access credentials for other authentication options.

Method definition

func (c *Client) ProcessObject(ctx context.Context, request *ProcessObjectRequest, optFns ...func(*Options)) (*ProcessObjectResult, error)

Resize an image and save the result

The Process field combines transformation directives with sys/saveas to save the output in one call. The target object key and bucket name in sys/saveas must be URL-safe Base64-encoded (o_ prefix for target object key, b_ prefix for target bucket name).

The following example resizes an image to a fixed 100x100 px and saves the result to the same bucket.

package main

import (
	"context"
	"encoding/base64"
	"flag"
	"fmt"
	"log"

	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
)

var (
	region     string
	bucketName string
	objectName string
)

func init() {
	flag.StringVar(&region, "region", "", "The region in which the bucket is located.")
	flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
	flag.StringVar(&objectName, "object", "", "The name of the object.")
}

func main() {
	flag.Parse()

	if len(region) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, region required")
	}
	if len(bucketName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, bucket name required")
	}
	if len(objectName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, object name required")
	}

	// Initialize the OSS client with credentials from environment variables.
	cfg := oss.LoadDefaultConfig().
		WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
		WithRegion(region)

	client := oss.NewClient(cfg)

	// Target bucket must be in the same region as the source bucket.
	targetBucketName := bucketName
	// If the target object is not in the bucket root, include the full path.
	targetImageName := "exampledir/example.jpg"

	// Build the process string:
	//   image/resize,m_fixed,w_100,h_100       — resize to a fixed 100x100 px
	//   sys/saveas,o_<base64>,b_<base64>        — save the result
	//     o_: target object key (URL-safe Base64-encoded)
	//     b_: target bucket name (URL-safe Base64-encoded)
	style := "image/resize,m_fixed,w_100,h_100"
	process := fmt.Sprintf("%s|sys/saveas,o_%v,b_%v",
		style,
		base64.URLEncoding.EncodeToString([]byte(targetImageName)),
		base64.URLEncoding.EncodeToString([]byte(targetBucketName)),
	)

	request := &oss.ProcessObjectRequest{
		Bucket:  oss.Ptr(bucketName),
		Key:     oss.Ptr(objectName),
		Process: oss.Ptr(process),
	}

	result, err := client.ProcessObject(context.TODO(), request)
	if err != nil {
		log.Fatalf("failed to process object %v", err)
	}

	log.Printf("process object result:%#v\n", result)
}

Add a blind watermark

The following example embeds a text blind watermark into an image using the blindwatermark directive.

package main

import (
	"context"
	"encoding/base64"
	"flag"
	"fmt"
	"log"

	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
)

var (
	region     string
	bucketName string
	objectName string
)

func init() {
	flag.StringVar(&region, "region", "", "The region in which the bucket is located.")
	flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
	flag.StringVar(&objectName, "object", "", "The name of the object.")
}

func main() {
	flag.Parse()

	if len(region) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, region required")
	}
	if len(bucketName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, bucket name required")
	}
	if len(objectName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, object name required")
	}

	// Initialize the OSS client with credentials from environment variables.
	cfg := oss.LoadDefaultConfig().
		WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
		WithRegion(region)

	client := oss.NewClient(cfg)

	// Build the process string:
	//   image/blindwatermark,content_<base64>   — embed a text blind watermark
	//     content_: watermark text (URL-safe Base64-encoded)
	//   sys/saveas,o_<base64>,b_<base64>        — save the result
	//     o_: target object key (URL-safe Base64-encoded)
	//     b_: target bucket name (URL-safe Base64-encoded)
	content := "Copyright Alibaba Cloud"
	targetImageName := "targetDir/target.jpg"

	style := fmt.Sprintf("image/blindwatermark,content_%s",
		base64.URLEncoding.EncodeToString([]byte(content)),
	)
	process := fmt.Sprintf("%s|sys/saveas,o_%s,b_%s",
		style,
		base64.URLEncoding.EncodeToString([]byte(targetImageName)),
		base64.URLEncoding.EncodeToString([]byte(bucketName)),
	)

	request := &oss.ProcessObjectRequest{
		Bucket:  oss.Ptr(bucketName),
		Key:     oss.Ptr(objectName),
		Process: oss.Ptr(process),
	}

	result, err := client.ProcessObject(context.TODO(), request)
	if err != nil {
		log.Fatalf("failed to process object %v", err)
	}

	log.Printf("process object result:%#v\n", result)
}

What's next

• Image processing parameters — full reference for all x-oss-process directives

• Synchronous processing — feature overview and limits

• ProcessObject API reference — complete API details on pkg.go.dev