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PNG images can be optimized in different ways.

Reducing PNG size for websites seems to be a good choice in order to reduce bandwidth usage and data transport (and reduce the impact on environment). It's recommended by Google and other services.

But does optimize PNG have an impact on CPU load when the computer read it to render it? In other words, is reducing PNG size to optimize size always a good idea to limit environment impact or is there some caveats?

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  • Dear downvoter, could you explain me why you downvoted? – rap-2-h Jul 12 '17 at 15:30
  • It's hard to see how reduced PNG file size could make any measurable impact on sustainability. – Earthliŋ Jul 12 '17 at 22:06
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    @Earthliŋ that clearly wasn't obvious to the asker though! Do you think a more general question would be better such as "Can website optimisation substantially reduce electricity use for web servers or users' computers?" – Highly Irregular Jul 13 '17 at 2:43
  • @HighlyIrregular I think that would be a better question. Of course this topic is always a difficult one. Is the time and effort spent to make something more "sustainable" really worth it? I guess in programming, this would correspond to the question of premature optimisation. – Earthliŋ Jul 13 '17 at 10:48
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It's a better question than it appears at first. Consider the amount of energy consumed by data centres, the proportion of data held and transferred in graphic formats and the increasing use of png. The effect on power usage in data centres and communication systems will be an important consideration for the decision makers. The end user's energy use, probably less so. The energy requirement at both ends will be affected by the level of compression. There's a good discussion about this here.

Modern computer devices are quite capable of dealing with the rendering without too much power usage. I would say that, having gained wide usage, this is a good format. I do most of my PC work on a "green" machine with a 10 Watt motherboard which is low in comparisons with most desktops. Large .jpgs are noticeable slow. I haven't noticed any problems with .png files and I have come to use the format routinely. Very large graphics in any format can slow things down as can uncompressed formats like bitmaps (.bmp).

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  • Welcome to Sustainable Living! You say "...rendering without too much power usage". Can you quantify your statements, or provide references to other work where this is explained? How would power consumption of transfer and rendering a .png image compare to transfer and rendering the same image in .jpg or .bmp? – THelper♦ Jul 13 '17 at 7:57
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    @THelper, I hope my edit improves the answer. The fact is that it's a very complex question and would require a lot of research and tests to provide a comprehensive answer. If you can raise the funding, I could probably find a phd to do the work. – Gannet Jul 14 '17 at 10:41
  • Thanks for your edit. It helps a bit, but I was really hoping to see some power consumption numbers. Perhaps no one investigated this so far. One would probably first need to determine some sort of 'standardized' hardware situation to make a good comparison. This could be difficult given the large variety of hardware that's available. – THelper♦ Jul 14 '17 at 14:04

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