Compression speed

[kuckir]

Hi,
I would like to encode large images (e.g. 8000 x 8000 pixels) into PNG. I tried to encode my image, which has 512x512 pixels, into PNG, resulting file had 38 kB and it took 1400 ms.
I tried the same thing via Canvas.toDataURL("image/png"), resulting file had 52 kB and it took 45 ms.

Do you think you can optimize your code a little, so it runs faster? Is there any way to change compression quality and make it run faster?