Image provides an abstract access to an arbitrary image , it defines a set of methods that can loggically be applied upon any implementation of Image. Its not bounded to any particular image format or implementation . Bitmap is a specific implementation to the image abstract class which encapsulate windows GDI bitmap object. Bitmap is just a specific implementation to the Image abstract class which relay on the GDI bitmap Object.
You could for example , Create your own implementation to the Image abstract , by inheriting from the Image class and implementing the abstract methods.
Anyway , this is just a simple basic use of OOP , it shouldn't be hard to catch.
This is a clarification because I have seen things done in code which are honestly confusing - I think the following example might assist others.
As others have said before - Bitmap inherits from the Abstract Image class
Abstract effectively means you cannot create a New() instance of it.
Image imgBad1 = new Image(); // Bad - won't compile
Image imgBad2 = new Image(200,200); // Bad - won't compile
But you can do the following:
Image imgGood; // Not instantiated object!
// Now you can do this
imgGood = new Bitmap(200, 200);
You can now use imgGood as you would the same bitmap object if you had done the following:
Bitmap bmpGood = new Bitmap(200,200);
The nice thing here is you can draw the imgGood object using a Graphics object
Graphics gr = default(Graphics);
gr = Graphics.FromImage(new Bitmap(1000, 1000));
Rectangle rect = new Rectangle(50, 50, imgGood.Width, imgGood.Height); // where to draw
gr.DrawImage(imgGood, rect);
Here imgGood can be any Image object - Bitmap, Metafile, or anything else that inherits from Image!
Source: Stackoverflow.com