Issue with rendering WriteableBitmap from Image in Silverlight

Question

I have a next problem, I need to convert array of bytes to WriteableBitmap with resize. I write next code.

private byte[] ResizeImage(byte[] array, double maxWidth, double maxHeight)
{
    WriteableBitmap wb = null;

    var stream = new MemoryStream(array);
    stream.Seek(0, SeekOrigin.Begin);
    var bmp = new WriteableBitmap(0, 0);
    bmp.SetSource(stream);
    stream.Close();
    var img = new Image();
    img.Source = bmp;
    double scaleX = 1;
    double scaleY = 1;
    if (bmp.PixelHeight > maxHeight)
    {
        scaleY = maxHeight / bmp.PixelHeight;
    }
    if (bmp.PixelWidth > maxWidth)
    {
        scaleX = maxWidth / bmp.PixelWidth;
    }
    wb = new WriteableBitmap(0, 0);
    var scale = Math.Min(scaleY, scaleX);
    wb.Render(img, new ScaleTransform() { ScaleX = scale, ScaleY = scale });
    wb.Invalidate();
    return Utils.Encode(wb);

}

After call wb.Render(img, new ScaleTransform() { ScaleX = scale, ScaleY = scale });, wb has zero pixels.

Help please.

score 1 · Answer 1 · answered Nov 29 '11 at 20:36

1

private byte[] ResizeImage(byte[] array, int maxWidth, int maxHeight)
{
    var stream = new MemoryStream(array);
    stream.Seek(0, SeekOrigin.Begin);

    var bmp = new BitmapImage();
    bmp.SetSource(stream);
    stream.Close();
    var img = new Image();
    img.Source = new BitmapImage();

    double scaleX = 1;
    double scaleY = 1;
    if (bmp.PixelHeight > maxHeight)
    {
        scaleY = maxHeight / bmp.PixelHeight;
    }
    if (bmp.PixelWidth > maxWidth)
    {
        scaleX = maxWidth / bmp.PixelWidth;
    }

    WriteableBitmap wb = new WriteableBitmap(maxWidth, maxHeight);
    var scale = Math.Min(scaleY, scaleX);
    wb.Render(img, new ScaleTransform() { ScaleX = scale, ScaleY = scale });
    wb.Invalidate();

    return Utils.Encode(wb);
}

answered Nov 29 '11 at 20:36

David

1,052
1
8
19

as I say it's not help all pixels has 0 value see image dl.dropbox.com/u/16517591/screen.png – Artem Holodnyak Nov 29 '11 at 20:45
That's not the only thing I changed. Try the code. I tested it and it works for me. – David Dec 01 '11 at 22:04
I try it, situation is the same – Artem Holodnyak Dec 04 '11 at 07:46

score 0 · Answer 2 · answered Nov 29 '11 at 20:07

0

Try changing:

wb = new WriteableBitmap(0, 0);

To:

wb = new WriteableBitmap(maxWidth, maxHeight);

answered Nov 29 '11 at 20:07

p.wilt

536
1
4
6

Issue with rendering WriteableBitmap from Image in Silverlight

2 Answers2