PVRTC format compromises image quality

Question

Hi,

For iPhone game development, I switched from PNG format to PVRTC format for the sake of performance. But PVRTC compression is ruining the quality of the images.. I am using spritesheets with transparencies for the character animations.. and the pvrtc makes the edges look muddy around the character near the transparencies.

I read that pvrtc cant handle edges and all.. but is there a solution to it? Can we do something to these images whereby atleast there wont be these muddy boundaries around the character..

Sankar

Answer 1

PVRTC is a lossy compression algorithm -- it will cause compression artifacts. If you can't or don't want to deal with that, don't use it. See if you can't find other places in your game to optimize instead.

Answer 2

Could you post a set of images comparing these two formats: PNG and PVRTC? It would be interesting to see an example of this "muddiness" and could help someone here figure out a solution to your problem.

I've only ever used PNG in my iPhone apps so I wouldn't have anything to compare it to.

Do you need to use PVRTC? By that I mean are you already having performance problems in your application that this is to solve?

Answer 3

Hi All,

Thanks for the comments. Actually I used this tool called PVRTexTool from Imagination Technologies. And that seemed to help a lot. This tool allowed a pre-processing in which I used the option of Bleed Texture with RGB being (0,0,0) over the PNG file and then created the PVR using that.. The resulting PVR had much better quality..

Of course it is not as perfect as PNG, but.. you cant have the cake and eat it too..

Sankar

Answer 4

Hi,

As all of you are discussing pvrtc texture format when i use a pvr image in my game it works fine but when i use thouse image over video that is playing the edges of the sprites glow. even when the video finishes playing and i replace the background with pvr image it still glows. i have those images have transparency does any one know why it is happening i use linear 4bpp compression for pvr images