FO-DICOM：在C＃Windows Forms应用程序中使用呈现的位图调整窗口大小会导致崩溃

Question

I have recently started to evaluate fo-dicom as a possible DICOM library for a future project, so I am quite new with it.

I built a basic C# Windows Forms application that only reads a DICOM file, converts it into a System.Drawing.Bitmap and displays in a PictureBox :

public partial class TestFoDicomForm : Form
{
    public TestFoDicomForm()
    {
        InitializeComponent();

        DicomImage di               = new DicomImage("Image_01.dcm");
        Bitmap bmp                  = di.RenderImage().AsBitmap();
        this._pbDicomImage.Image    = bmp;
    }
}

This code functions, but if I start to resize the form, an exception comes more earlier than later telling:

System.ArgumentException: Parameter is not valid.

at System.Drawing.Image.get_RawFormat()
at System.Drawing.Graphics.DrawImage(Image image, Int32 x, Int32 y, Int32 width, Int32 height)
at System.Drawing.Graphics.DrawImage(Image image, Rectangle rect)
at System.Windows.Forms.PictureBox.OnPaint(PaintEventArgs pe)
at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer)
at System.Windows.Forms.Control.WmPaint(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

The exception occurs actually in Main()

Application.Run(new TestFoDicomForm());

but I was unable to add a functioning try/catch to investigate what effectively happens.

I added the reference to fo-dicom 3.0.2 via NuGet (the project's target framework being 4.6.1). Environment: Windows 10 Pro, VS 2017.

An interesting thing is that if I produce the bitmap as shown in the code above, then store it, and in the application read it (with no reference to DICOM) and place into the picture box, nothing similar happens. This makes me to think that the problem lies in the bitmap itself, but I was unable to discover, what.

I also have an old test application made with fo-dicom.1.0.37 which does not crash when being resized.

I am very curious what the reason may be, how to get rid of this effect or/and what is it I am possibly doing wrong.

(The test application can be downloaded - I hope - from http://jmp.sh/UGOg8Ai ).

Answer 1

This is a known issue in fo-dicom and there is already a fix, that will be included in the next release. The explanation is, that the AsBitmap() method returns a Bitmap, whose pixel data points to a memory that is owned by the IImage instance. If the IImage instance disposes, then the pointer of the Bitmap is invalid. This is great for performance reasons and memory consumption because the pixeldata does not have to be duplicated. Therefore this is not a bug, but as designed.

The new release will have two methods: one das behaves like currently to have best performance, and an other that returns a Bitmap with its own pixel data copied.

If you have suggenstions or comments, feel free to add them to the issue on github:

https://github.com/fo-dicom/fo-dicom/issues/634

Answer 2

A colleague of mine knew the answer. The following code does the thing:

public partial class TestFoDicomForm : Form
{
    private IImage image;

    public TestFoDicomForm()
    {
        InitializeComponent();

        this.image = new DicomImage("Image_01.dcm").RenderImage();
        Bitmap bmp = image.AsBitmap();
        this.pictureBox1.Image  = bmp;
    }
}

The trick here is that you need to save the instance of your IImage (necessarily in this form, as IImage , due to the return type of RenderImage() ).