error in editing byte[] from images

I'm trying to do image processing on wp7, and now i finished convertImagetoBytes and convertByteToBitmapImage.

I suppose I can change the values in the byte array to do some image processing work, but it turns out to be a black image in the picturebox. (Now I just wanna process .jpg images)

convertImagetoBytes

byte[] data = null;

using (MemoryStream stream = new MemoryStream())
{
    WriteableBitmap wBitmap = new WriteableBitmap(bitmapImage);
    wBitmap.SaveJpeg(stream, wBitmap.PixelWidth, wBitmap.PixelHeight, 0, 100);
    stream.Seek(0, SeekOrigin.Begin);
    data = stream.GetBuffer();
}

convertBytestoImage

Memo开发者_如何学JAVAryStream stream = new MemoryStream(bytes);
stream.Position = 0;
BitmapImage bi = new BitmapImage();
bi.SetSource(stream);
return bi;

now if i change the values in the byte array,just like this(grayscale)

for (int i = 0; i < bytesCount; i+=4)
{
     colorTemp = data[i+2];
     data[i+1 ] =data[i+2]= data[i + 3] = (byte)colorTemp;
}

the image turns out to be black.

---

You've saved it as a JPEG - but you appear to be trying to change it as if it were raw data. You can't just mess around with the data of a JPEG file to fake greyscale.

By the way, you should use stream.ToArray instead of stream.GetBuffer() as the latter will usually be larger than the real data.

---

You should also look into using René Schulte's WriteableBitmapEx library.

And consider reading this article about a Windows Phone Picture Effects Application