# Exporting Images in .NET Standard

The .NET Standard specification does not define APIs for getting image properties. SpreadProcessing needs access to GDI+ basic graphics functionality when exporting spreadsheets that contain images. To allow the library to get the image properties needed for saving the workbook, set an implementation inheriting the `ImagePropertiesResolverBase` abstract class to the `ImagePropertiesResolver` property of `SpreadExtensibilityManager`.

> note The **Telerik.Documents.ImageUtils** package provides a default implementation of the `ImagePropertiesResolver` class that you can use when exporting the document.

**Example 1: Set the default ImagePropertiesResolver implementation**

```C#
ImagePropertiesResolverBase imagePropertiesResolver = new ImagePropertiesResolver();
SpreadExtensibilityManager.ImagePropertiesResolver = imagePropertiesResolver;
```

**Example 2: Create a custom ImagePropertiesResolver implementation for Windows**

```C#
public class ImageInfo : ImagePropertiesResolverBase
{
    public override Size GetImageSize(byte[] imageData)
    {
        Size size = Size.Empty;
        try
        {
            using (SKBitmap decodedBitmap = SKBitmap.Decode(imageData))
            {
                size = new Size(decodedBitmap.Width, decodedBitmap.Height);
            }
        }
        catch (Exception ex)
        {
            // Image format not recognized.
            throw new NotSupportedException("Unsupported image format.", ex);
        }

        return size;
    }

    public override bool TryGetRawImageData(byte[] imageData, out byte[] rawRgbData, out byte[] rawAlpha, out Size size)
    {
        using (SKBitmap decodedBitmap = SKBitmap.Decode(imageData))
        {
            size = new Size(decodedBitmap.Width, decodedBitmap.Height);

            GetRawDataFromRgbaSource(decodedBitmap, out rawRgbData, out rawAlpha);

            return true;
        }
    }

    private static void GetRawDataFromRgbaSource(SKBitmap decodedBitmap, out byte[] data, out byte[] alpha)
    {
        bool shouldExportAlpha = false;

        List<byte> rawRgbData = new List<byte>(decodedBitmap.ByteCount / 4 * 3);
        List<byte> rawAlpha = new List<byte>(decodedBitmap.ByteCount / 4);

        SKColor[] pixels = decodedBitmap.Pixels;
        for (int i = 0; i < pixels.Length; i++)
        {
            SKColor pixel = pixels[i];
            byte r = pixel.Red;
            byte g = pixel.Green;
            byte b = pixel.Blue;
            byte a = pixel.Alpha;

            rawRgbData.Add(r);
            rawRgbData.Add(g);
            rawRgbData.Add(b);
            rawAlpha.Add(a);

            if (a != 255)
            {
                shouldExportAlpha = true;
            }
        }

        data = rawRgbData.ToArray();
        alpha = rawAlpha.ToArray();

        if (!shouldExportAlpha)
        {
            alpha = null;
        }
    }
}
```

**Example 3: Register a custom ImagePropertiesResolver implementation**

```C#
ImagePropertiesResolverBase imagePropertiesResolver = new ImageInfo();
SpreadExtensibilityManager.ImagePropertiesResolver = imagePropertiesResolver;
```

## See Also

* [Cross-Platform Support](https://www.telerik.com/document-processing-libraries/documentation/libraries/radspreadprocessing/cross-platform-support/cross-platform)
* [What is a Workbook?](https://www.telerik.com/document-processing-libraries/documentation/libraries/radspreadprocessing/working-with-workbooks/working-with-workbooks-what-is-workbook)
* [What is a Worksheet?](https://www.telerik.com/document-processing-libraries/documentation/libraries/radspreadprocessing/working-with-worksheets/what-is-worksheet)
* [Get, Set and Clear Cell Properties](https://www.telerik.com/document-processing-libraries/documentation/libraries/radspreadprocessing/working-with-cells/get-set-clear-properties)
* [Using XlsxFormatProvider](https://www.telerik.com/document-processing-libraries/documentation/libraries/radspreadprocessing/formats-and-conversion/import-and-export-to-excel-file-formats/xlsx/xlsxformatprovider)
* [Using PdfFormatProvider](https://www.telerik.com/document-processing-libraries/documentation/libraries/radspreadprocessing/formats-and-conversion/pdf/pdfformatprovider)
* [PdfProcessing Library Documentation](https://www.telerik.com/document-processing-libraries/documentation/libraries/radpdfprocessing/overview)