How do I use large bitmaps in .NET?

Question

I'm trying to write a light-weight image viewing application. However, there are system memory limitations with .NET.

When trying to load large bitmaps (9000 x 9000 px or larger, 24-bit), I get a System.OutOfMemoryException. This is on a Windows 2000 PC with 2GB of RAM (of which 1.3GB is used up). It also takes a lot of time to attempt loading the files.

The following code generates this error:

Image image = new Bitmap(filename);
using (Graphics gfx = this.CreateGraphics())
{
    gfx.DrawImage(image, new Point(0, 0));
}

As does this code:

Stream stream = (Stream)File.OpenRead(filename);
Image image = Image.FromStream(stream, false, false);
using (Graphics gfx = this.CreateGraphics())
{
    gfx.DrawImage(image, new Rectangle(0, 0, 100, 100), 4000, 4000, 100, 100, GraphicsUnit.Pixel);
}

Also, it is enough to do just this:

Bitmap bitmap = new Bitmap(filename);
IntPtr handle = bitmap.GetHbitmap();

The latter code was intended for use with GDI. While researching this, I found out that this is in fact a memory issue where .NET tries to allocate twice as much as is needed in a single contigous block of memory.

http://bytes.com/groups/net-c/279493-drawing-large-bitmaps

I know from other applications (Internet Explorer, MS Paint etc.) that it IS possible to open large images, and rather quickly. My question is, how do I use large bitmaps with .NET?

Is there anyway to stream them, or non-memory load them?

Answer 1

One thing just struck me. Are you drawing the entire image and not only the visible part? You should not draw a bigger portion of the image than you are showing in your application, use the x, y, width and heigth parameters to restrict the drawn area.