I see, got it! Size around 1-2 MB not bad. But when I press the share button and use Iutlook, size becomes 300+ KB only. Hmm
WP compressed the pictures to save bandwidth, when sent through emails. This makes me frustrated too, there would be an option to toggle this. When on other phones or devices, WhatsApp and Facebook also compresses the pictures. You can try looking in your WhatsApp folder, from your computer.