Upload any size image into carousel I wanted to create a php which allow admin to upload their pictures in any resolution and image file type, but it has to display into a bootstrap carousel with fixed size. 
Does anyone has the similar script I can have a look?

It might needed to do the following;
Upload image into a specific location, convert image type into jpg, specific resolution, and be able to read by bootstrap carousel. My head is about to broke thinking of this script :(
You shouldn't need to create a custom plugin to do that.

You can easily create a Matrix content field for your carousel. Create a new block called slide. From there you can create an asset field to upload the slide image.

You can render this into whatever markup you'd like (even bootstrap).

As for cropping an image and converting it into a jpg, check out Aviary Image Editor. It's a wysiwyg editor in the admin panel for doing exactly what you are looking for.