Coding Journal

Andy Beaulieu had posted how to "print" from Silverlight 3 using a WriteableBitmap that's converted to a png image (post here.) I wanted to use a jpeg image. After looking around found the FJCore library which provides jpeg encoding/decoding. After struggling with how to convert the pixel array from WriteableBitmap to the format that FJCore expects I finally got it working. Here is the code if anyone is interested.

private static string GetBase64Jpg(WriteableBitmap bitmap)
{
    int width = bitmap.PixelWidth;
    int height = bitmap.PixelHeight;
    int bands = 3;
    byte[][,] raster = new byte[bands][,];

    for (int i = 0; i < bands; i++)
    {
        raster[i] = new byte[width, height];    
    }

    for (int row = 0; row < height; row++)
    {
        for (int column = 0; column < width; column++)
        {
            int pixel = bitmap.Pixels[width * row + column];
            raster[0][column, row] = (byte)(pixel >> 16);
            raster[1][column, row] = (byte)(pixel >> 8);
            raster[2][column, row] = (byte)pixel;
        }
    }

    ColorModel model = new ColorModel { colorspace = ColorSpace.RGB };
    FluxJpeg.Core.Image img = new FluxJpeg.Core.Image(model, raster);
    MemoryStream stream = new MemoryStream();
    JpegEncoder encoder = new JpegEncoder(img, 90, stream);
    encoder.Encode();

    stream.Seek(0, SeekOrigin.Begin);
    byte[] binaryData = new Byte[stream.Length];
    long bytesRead = stream.Read(binaryData, 0, (int)stream.Length);

    string base64String =
            System.Convert.ToBase64String(binaryData,
                                          0,
                                          binaryData.Length);

    return base64String;
}

silverlight 3 writeablebitmap