Image vs Bitmap class

I have trouble understanding the differences between the Image class and the Bitmap class. Now, I know that the Bitmap inherits from the Image but from what I understand both are very similar. Can anyone shed some light on this please?

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最佳答案

The Bitmap class is an implementation of the Image class. The Image class is an abstract class;

The Bitmap class contains 12 constructors that construct the Bitmap object from different parameters. It can construct the Bitmap from another bitmap, and the string address of the image.

See more in this comprehensive sample.

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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.

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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!


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