Help Weird display

[dipz]

Since last few days, display on my S4 mini goes weird; it shows patches of different colours usually on dark shades. This is observed randomly, and turns ok in few minutes.

I observed:
- this started happening after kitkat update
- doesn't occur in cool (air conditioned) atmosphere

Is this hardware problem?

~dipz

 

[dipz]

I have reset it to factory default, but problem remains, so it was not software fault at all, it must be some hardware issue.

~dipz