Corrupted File when I save a Bitmap image on HardDrive

Question

I have a Silverlight Out-of-browser application and I want to save pictures on a specified directory. In the application, I have the picture loaded in a BitmapImage and I wish to save it on the HardDrive (in jpg if possible). My code :

private void SaveImageToImagePath(BitmapImage image)
{
    string path = System.IO.Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "Images");
    if (!Directory.Exists(path))
    {
        Directory.CreateDirectory(path);
    }

    Save(image, new FileStream(Path.Combine(path, String.Format("{0}.jpg", _imageName)), FileMode.OpenOrCreate));
}

private void Save(BitmapSource bitmapSource, FileStream stream)
{
    var writeableBitmap = new WriteableBitmap(bitmapSource);

    for (int i = 0; i < writeableBitmap.Pixels.Length; i++)
    {
        int pixel = writeableBitmap.Pixels[i];

        byte[] bytes = BitConverter.GetBytes(pixel);
        Array.Reverse(bytes);

        stream.Write(bytes, 0, bytes.Length);
    }
} 

I have also tried with this method to pass from BitmapImage to ByteArray:

private byte[] ToByteArray(WriteableBitmap bmp)
{
    // Init buffer 
    int w = bmp.PixelWidth;
    int h = bmp.PixelHeight;
    int[] p = bmp.Pixels;
    int len = p.Length;
    byte[] result = new byte[4 * w * h];

    // Copy pixels to buffer 
    for (int i = 0, j = 0; i < len; i++, j += 4)
    {
        int color = p[i];
        result[j + 0] = (byte)(color >> 24); // A 
        result[j + 1] = (byte)(color >> 16); // R 
        result[j + 2] = (byte)(color >> 8);  // G 
        result[j + 3] = (byte)(color);       // B 
    }

    return result;
} 

The problem is that the file I get is unreadable (corrupted) and when I try to read it from the application, I got a Catastrophic Failure. I also noticed that the file generated by the application is four time heavier than the original...

Thank you for your help !

Philippe

Sources :

Can I get a byte[] from a BitmapImage in Silverlight?

Silverlight: image to byte[]

Answer 1

A JPG file is a complex set of compressed data, optimized to give the best compression for photo-realistic images. It does this by identifying patterns of colour in square areas throughout the image and removing redundancy.

It is not just a set of RGB values, but you are simply writing the pixel byte values out to a file. What you are writing is basically a RAW image file. If you load a photo tool that reads RAW image files (and specify the size) you will be able to view it but that is not the problem you are trying to solve.

Your best bet in Silverlight is to save them to PNG files using a PNGEncoder or maybe .Net Image Tools, else you will need to find another custom library that can duplicate JPG compression/saving.