Why should I use PNG and not JPG?

Question

I'm building an app that uses a lot of images, so it's getting pretty big. I got more than 15mb in PNG images, and if I convert those images to JPG I would get 5MB or less! So, why should I use PNG instead of JPG?

I know that PNGs are preferred, but what would I lose with JPG?

EDIT: Thank you everybody!

Just a note: Since I got my answer and turns out that I will need to use PNG in most files, I found out that website http://tinypng.org/ , and that's helping me a lot. My 15mb of images are now 7mb. So, if anyone is in the same situation that I am, I hope that it helps!

Solution 1

Major reason - PNG will give you advantage of Alpha Transparency over JPG.

Also see: PNG vs. GIF vs. JPEG vs. SVG - When best to use?

Solution 2

PNGs are smaller for images a few solid colors (solid polygons) (because they make JPEG artifacts more obvious) JPEGs are better for photos and other images that don't have consistent patterns (JPEG artifacts are harder to notice here)

Comments

[leonbloy]

"important software like Photoshop have very poor implementation of the format" Some details or references about that?

[Adrian Pronk]

@leonbloy: See: graphicdesign.stackexchange.com/questions/5888

[Kornel]

@leonbloy Photoshop doesn't support Index+Alpha combination that gives smallest files with alpha.