When i started my blog,i learned many famous blogs like Techcrunch,Techdirt,Read write web, Shoutmeloud.After noticing these blogs i found something interesting,there was a things which were common in all these blogs.In each of these blogs a picture comes on a page is smaller in size but when we click on the post to read the full article, i found that the size of image become bigger. I was unable to understant how this happen and how could i apply on a website.Thanks to @Nitesh who found the wordpress plugin for the same.
I am talking about a very ultimate wordpress plugin “WP thumbnail”,by installing this plugin you will get an option in the dashboard footer part to select the thumbnail and crop it.WP Post Thumbnail plugin adds an image upload, crop and save panel in ‘Write Post’ screen. It allows you to easily upload a .jpg image file. Once the image file is uploaded, you can crop it before saving it as your thumbnail.
Spend less time messing around with Photoshop everytime you need to make a thumbnail (or two) for your post. Also, saves you time and trouble from manually copy-and-pasting uploaded image URLs into custom key value fields.
now when you will download and install an option will shown under your post and will look like this then you just have to upload an image and crop it.
the croped image will something look like this and select the area and save it and you are donw with this.
Need of thumbnail plugin
So what is the need of thumbnail instead of full image,but it is to be noted that bigger image means more memory and more heavy page. So your website could take time to open if you are not using this plugin.