Tutorial: How to Resize Images with Aspose.Imaging Cloud

Learning Objectives

In this tutorial, you’ll learn how to:

Resize images by specifying new width and height
Optionally convert the image format during resizing
Implement image resizing both with and without cloud storage

Prerequisites

Before you begin this tutorial, make sure you have:

An Aspose Cloud account (obtain a free trial here)
Your Client ID and Client Secret from the dashboard
Basic understanding of REST API concepts
Your preferred development environment set up (.NET, Java, or cURL)

Practical Use Case

Image resizing is essential in numerous applications:

Creating thumbnails for media galleries
Optimizing images for web pages to improve loading speed
Preparing images for specific display dimensions on different devices
Standardizing image sizes in a collection

Tutorial Steps

Step 1: Understanding Image Resize API Options

Aspose.Imaging Cloud provides two API endpoints for resizing images:

With Storage (GET method): Upload your image to Cloud Storage first, then resize it using its name.
- Endpoint: GET /imaging/{name}/resize
Without Storage (POST method): Directly send your image in the request body for resizing.
- Endpoint: POST /imaging/resize

Both methods allow you to specify new dimensions and optionally change the output format.

Step 2: Authentication

Before making API calls, you need to obtain a JWT token:

curl -v "https://api.aspose.cloud/connect/token" \
-X POST \
-d 'grant_type=client_credentials&client_id=YOUR_CLIENT_ID&client_secret=YOUR_CLIENT_SECRET' \
-H "Content-Type: application/x-www-form-urlencoded" \
-H "Accept: application/json"

Save the returned JWT token for use in subsequent API calls.

Step 3: Resize an Image (With Storage)

3.1 First, upload your image to cloud storage

curl -X PUT "https://api.aspose.cloud/v3/imaging/storage/file/image.jpg" \
-H "Authorization: Bearer YOUR_JWT_TOKEN" \
-H "Content-Type: application/octet-stream" \
-T /path/to/your/image.jpg

3.2 Resize the uploaded image

curl -v "https://api.aspose.cloud/v3/imaging/image.jpg/resize?format=png&newWidth=400&newHeight=300" \
-X GET \
-H "Content-Type: application/json" \
-H "Accept: application/json" \
-H "Authorization: Bearer YOUR_JWT_TOKEN" \
-o resized_image.png

Step 4: Resize an Image (Without Storage)

For quick one-off resizing without storing the image first:

curl -v "https://api.aspose.cloud/v3/imaging/resize?format=png&newWidth=400&newHeight=300" \
-X POST \
-T /path/to/your/image.jpg \
-H "Content-Type: application/json" \
-H "Accept: application/json" \
-H "Authorization: Bearer YOUR_JWT_TOKEN" \
-o resized_image.png

Try It Yourself

Now it’s your turn! Choose an image from your computer and try:

Resizing it to 300x200 pixels
Changing its format to PNG if it’s not already in PNG format
Trying both the storage and non-storage methods

Remember to replace the placeholder values with your actual image path, JWT token, and desired parameters.

SDK Implementation Examples

C# (.NET) Example

// Resize an image in cloud storage
public static void ResizeImageInCloud()
{
    // Get your clientId and clientSecret from https://dashboard.aspose.cloud/
    var imagingApi = new ImagingApi("YOUR_CLIENT_ID", "YOUR_CLIENT_SECRET");
    
    try
    {
        // Upload an image to cloud storage (required for this example)
        string localInputImage = "YourImage.jpg";
        string uploadedImageName = "sample_image.jpg";
        string cloudFolder = "imaging_samples";
        
        using (FileStream imageStream = new FileStream(localInputImage, FileMode.Open))
        {
            UploadFileRequest uploadRequest = 
                new UploadFileRequest(cloudFolder + "/" + uploadedImageName, imageStream);
            imagingApi.UploadFile(uploadRequest);
        }
        
        // Set resize parameters
        int newWidth = 400;
        int newHeight = 300;
        string format = "png"; // Convert to PNG format
        
        // Create request to resize the image
        ResizeImageRequest request = new ResizeImageRequest(
            uploadedImageName, newWidth, newHeight, format, cloudFolder);
            
        // Perform the resize operation
        using (var resultStream = imagingApi.ResizeImage(request))
        {
            // Save the resized image to a local file
            using (FileStream fileStream = 
                new FileStream("resized_image.png", FileMode.Create))
            {
                resultStream.CopyTo(fileStream);
            }
        }
        
        Console.WriteLine("Image has been successfully resized!");
    }
    catch (Exception ex)
    {
        Console.WriteLine("Error: " + ex.Message);
    }
}

Java Example

// Resize an image in the request body
public static void resizeImageWithoutStorage() throws Exception 
{
    // Get your clientId and clientSecret from https://dashboard.aspose.cloud/
    ImagingApi imagingApi = new ImagingApi("YOUR_CLIENT_ID", "YOUR_CLIENT_SECRET");
    
    try 
    {
        // Specify the local image file path
        String localInputImage = "YourImage.jpg";
        
        // Prepare parameters for resize operation
        int newWidth = 400;
        int newHeight = 300;
        String format = "png"; // Convert to PNG format
        
        // Read the image into a byte array
        byte[] imageData = Files.readAllBytes(Paths.get(localInputImage));
        
        // Create request for resize operation
        CreateResizedImageRequest request = 
            new CreateResizedImageRequest(imageData, newWidth, newHeight, format, null);
        
        // Perform the resize operation
        byte[] resultImage = imagingApi.createResizedImage(request);
        
        // Save the resized image to a local file
        Files.write(Paths.get("resized_image.png"), resultImage);
        
        System.out.println("Image has been successfully resized!");
    } 
    catch (Exception e) 
    {
        System.out.println("Error: " + e.getMessage());
        e.printStackTrace();
    }
}

Troubleshooting Tips

Authentication Errors: Ensure your Client ID and Client Secret are correct and your subscription is active.
404 Not Found: Check if the image path in cloud storage is correct.
Invalid Dimensions: Width and height must be positive integers.
Format Support: Not all image formats support all operations. Check format support documentation for compatibility.

What You’ve Learned

In this tutorial, you’ve learned how to:

Authenticate with the Aspose.Imaging Cloud API
Resize images by specifying new width and height
Convert image formats during the resize operation
Implement resizing with both storage and non-storage approaches
Handle the API responses to save the resized image

Further Practice

To strengthen your understanding, try these additional exercises:

Create a thumbnail generator that resizes multiple images to the same dimensions
Implement proportional resizing (maintaining aspect ratio)
Integrate error handling for various edge cases

Next Tutorial

Ready to learn more? Continue to our Crop Images Tutorial to discover how to extract specific portions of an image.

Helpful Resources

Have questions about this tutorial? Feel free to visit our forum for assistance.