Scsl.Drawing 8.0.17

How to Use the ConvertImageToWebp Extension Method

This guide explains how to use the ConvertImageToWebp extension method to convert an uploaded image file (IFormFile) into WebP format.

Method Definition

public static Task<MemoryStream> ToWebpFormat(this IFormFile formFile, int quality = 75)

Parameters

• formFile: An instance of IFormFile representing the uploaded file. It must be an image file.
• quality (optional): An integer between 1 and 100 specifying the quality of the Webp image (default is 75)

Returns

• A Task<MemoryStream> containing the converted image in Webp format.

Prerequisites

1. Library Reference: Ensure you have the Scsl.Drawing library installed for image processing. You can install it via NuGet:

dotnet add package Scsl.Drawing

2. Webp Encoder: The method uses ConvertImageToWebp and ConvertImageToWebpAsync, which is part of Scsl.Drawing.

Usage Exmaple

Here is an example of how to use the ConvertImageToWebp extension method in an ASP.NET Cor application:

1. Accept an Image File in the a Controller:

[HttpPost("upload-image")]
public async Task<IActionResult> UploadImage(IFormFile file)
{
    try
    {
        // Convert the uploaded image to WebP format
        MemoryStream webpStream = await file.ConvertImageToWebpAsync(80);

        // Example: Save the WebP file to disk (optional)
        var filePath = Path.Combine("wwwroot", "images", "converted-image.webp");
        await System.IO.File.WriteAllBytesAsync(filePath, webpStream.ToArray());

        return Ok(new { Message = "Image converted to WebP successfully.", Path = filePath });
    }
    catch (Exception ex)
    {
        // Handle exceptions (e.g., invalid file format)
        return BadRequest(new { Message = ex.Message });
    }
}

2. Client-Side Example (Postman or cURL):

Send POST request with an image file:

curl -X POST "http://localhost:5000/upload-image" -F "file=@path-to-image.jpg"

Detailed Behavior

1. Input Validation

• If the formFile is null, an ArgumentNullException is thrown.
• If the file is not an image, a UnknownImageFormatException is thrown.
• if the image quality is less than 1 and greater than 100, a FormatException is thrown.

2. Conversion

• The input image is loaded into memory
• It is than encoded in Webp format using the specified quality setting.

3. Output

• The converted image is returned as a MemoryStream, ready to be saved or processed further.

Notes

• Supported Formats: The input file must be an image format supported by Scsl.Drawing (e.g., JPG, PNG, JPEG, etc.).
• Peformanace: Webp compression can be computationally intensive for large images. Consider handling large file asynchronously.

Common Issues

1. Unsupported File Format:

• Error File format is not supported.
• Solution: Ensure the uploaded file's Content-Type starts with "image/".