Godot generates PVRTC-compressed texture with all zeros

[DrMoriarty]

Godot version:
Godot 3.2.2.beta1

OS/device including version:
MacOSX 10.14.6 (18G95)

Issue description:
Set texture VRAM compressed, enable pvrtc compression. Reimport texture, after GDST header it contains only zeros.

Original file:

Compressed file:

background.png-14973fd1de8b151436931643db6aa461.pvrtc.stex.zip

Steps to reproduce:

Minimal reproduction project:

[DrMoriarty]

It was broken after 3.1.1
For example this file generated by godot-3.1.1.stable:
background.png-14973fd1de8b151436931643db6aa461.pvrtc.stex.zip

[DrMoriarty]

I'm trying to fix it and it seems that our pvrtc encoder completely broken.
So my game looks on an emulator:

And this is screenshot from iphone:

One texture (container in the center of screen) is vram packed.

[Zireael07]

IIRC VRAM packing isn't supported on mobiles?

[DrMoriarty]

@Zireael07 what is it IIRC?

[Zireael07]

IIRC = If I recall correctly

[DrMoriarty]

@Zireael07 therefore there is a reason to make it workable.

[Calinou]

Related to #28669, #28683?

[DrMoriarty]

@Calinou yes, exactly. Now I'm working on new pvrtc compressor for godot. Hope it will be ready in couple of days.