Displaying full size image may effect your Blogger Layout. So, you are also suggested to display compressed form of a Full Size Picture. Compressed form will display a HQ image with actual resolution and will fit the image in your post body. For Example: If you upload 1024x760 pixels wallpaper, This full size wallpaper may effect your blogger layout. So, its important to display a compressed version of the image. You can choose any compression size that fits for your blog post body.

Suppose you choose 600px compression width size. All images will be displayed in 600px width and height will be set automatically. Whenever some one will Right Click and Save the picture, they will get the image in Original Resolution.


How to Compress the Size of Full Size Images
Go to Your Blogger Account > Dashboard > Desgin > EDIT HTML
Find This Code
]]></b:skin>
 Replace this code with
img { max-width: 560px; width: expression(this.width > 560 ? 560: true); } ]]></b:skin>

Save the Template and its Done :)

You can change 560 according to size of your Post body.


Troubleshoot:
If this does not work for you, then it means your template is already using img parameter in stylesheet. Follow this tip then.

Search for img { and replace it with this new code
img { max-width: 560px; width: expression(this.width > 560 ? 560: true);
Save Your Template and Its done.
Thats it

This is not only for Blogger. You can use this for WordPress and other web pages as well using Troubleshoot method.