Cropping a bitmap gives an empty bitmap

I've taken a code from here (SO) that crops images. I tried it o开发者_运维知识库n bitmaps containing black text on white font. The result i get in return is a completely white output with no content.

        // create new bitmap with desired size and same pixel format
        Bitmap croppedBitmap = new Bitmap(rect.Width, rect.Height, bitmap.PixelFormat);

        // create Graphics "wrapper" to draw into our new bitmap
        // "using" guarantees a call to gfx.Dispose()
        using (Graphics gfx = Graphics.FromImage(croppedBitmap))
        {
            // draw the wanted part of the original bitmap into the new bitmap
            gfx.DrawImage(bitmap, 0, 0, rect, GraphicsUnit.Pixel);
        }

        return croppedBitmap;

Any guess?

PS if i crop in paint of course it does work

edit

If I crop a picture of me for example it works....

Appendix

Code:

Rectangles:

        Rectangle 1: 8 50, 95, 80, 30 // invoice number
        Rectangle 2: 625, 778, 475, 22 // Total amount

CropImage():

    public static Bitmap CropImage(Bitmap bitmap, Rectangle rect)
    {
        Bitmap croppedBitmap = new Bitmap(rect.Width, rect.Height, bitmap.PixelFormat);

        using (Graphics gfx = Graphics.FromImage(croppedBitmap))
        {
            gfx.DrawImage(bitmap, 0, 0, rect, GraphicsUnit.Pixel);
        }

        return croppedBitmap;
    }

Image: (Sensitive data is hidden, I only left the part I'm trying to crop) http://img33.imageshack.us/img33/5703/modelx.png

Fixed code:

    Rectangle rect = new Rectangle(625, 778, 475, 22);

    Bitmap bitmap = Bitmap.FromFile(@"C:\m.png") as Bitmap;

    Bitmap croppedBitmap = new Bitmap(bitmap, rect.Width, rect.Height);
    croppedBitmap.SetResolution(bitmap.HorizontalResolution, bitmap.VerticalResolution);

    using (Graphics gfx = Graphics.FromImage(croppedBitmap))
    {
        gfx.DrawImage(bitmap, 0, 0, rect, GraphicsUnit.Pixel);
    }

    croppedBitmap.Save(@"C:\m-1.png", System.Drawing.Imaging.ImageFormat.Png);