Google won’t thank you for it, any more than your customers will. Worse still WordPress may well throw overly large image files straight out of the pram.
Large image files slow websites down. Google increasingly penalises poor page speed and your viewers will tire of slow pages. The bottom line it is good practice to optimise your images before you upload them. PicNik will let you resize and edit your image and save a copy back to your computer ready to upload to your website or blog.
This video is part of a series aimed at those new to WordPress
Footnote, Unfortunately the bottom of the screen has been trimmed, there is a dialogue box that gives the image dimensions (bottom right). Also when I am referring to the screen size (1440 x 900) it is for the mac that I am working on, yours may differ.