I have 2 images.
The first one (@2x: 50x50, 72 pixels/ inches) is like this:
It look so ugly in Tab Bar:
The second one (@2x: 48x42, 72 pixels/inches) is like this:
Even it is smaller, it look good in Tab Bar:
I cannot see the different between the 2 images. Can you see and tell me why? I'm new in designing images for iphone. How can I design good image for tab bar? Here you can download the images.
After hours of researching finally I found out the reason. It's so silly of myself but I have to post this with hope that it will save time for other iOS developers who also want to design their own app:
Basically when exporting images to be used inside your app, your need to export with with PNG-24 type. That's all. (See image below as an example).