How to Change Thumbnail Sizes in WordPress
Wordpress will create several thumbnails automatically when we upload an image to our website. You can see so many thumbnails generated by wordPress, but the default sizes are not suitable for most of us apparently. Then we need to change the default settings in WordPress. Usually image size should not exceed the content width. So I want to close or prohibit thumbnail generation. For many bloggers, It seems there is no need of generating three types of thumbnails if he or she only concerns content, but not appearance. It is very simple to prohibit thumbnail generation in wordpress, follow these steps:
1. Log in your wordpress dashboard.
2. Click Settings->Media. Screenshot as:
Set Thumbnail size, Medium size and Large size's values to a proper size as you want it to be. then press Save changes to make them to take effect.
If you set one of them to zeros, Wordpress will not generate that type thumbnails anymore. for example, I set Large size Max Width=0, Max Height=0, then the large size thumbnail will not be see even I upload a 2304*3456 image to the website.
Note: When thumbnail generation is closed, you can not use Thumbnail, Medium, Large function(Screenshot shown above), all the pictures that will be insert into post are in full size. So you must pay attention to the original picture size, make sure it does not exceed the theme's limitation.