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AppGameKit Classic Chat / Using SaveImage() can massively reduce the file size!!!

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Scraggle
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Posted: 17th Feb 2016 11:01
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I was just doing a simple test and discovered a rather bizarre but very welcome 'feature'.
SaveImage() can (in some cases) massively reduce the size of the PNG file. It isn't always the case - sometimes it is slightly bigger but I noticed that in many case the file size was more than halved!

Images that other people have created don't seem to benefit as much as ones that I create myself, so maybe it is Photoshop that is creating large files but it's still worth trying this on your images if you want to reduce the file size:



As an experiment, I tried several methods of saving a PNG from Photoshop.
No compression - 281,937 bytes
Compression, no interlace - 33,419 bytes
Compression, interlaced - 37,479 bytes
SaveImage() from AppGameKit - 15,381 bytes !!!!
AGK V2 user - Tier 1 (mostly)
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Digital Awakening
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Posted: 17th Feb 2016 12:13
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Try saving the PNG as 8 or 16 bit in Photoshop. Unless you need 32 bit? PS do add extra info to the file and there are programs available that can remove the extra info.
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JohnnyMeek
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Posted: 17th Feb 2016 12:24
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Or try this...

https://tinypng.com/

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Scraggle
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Posted: 17th Feb 2016 12:38
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Good tip!
TinyPNG is amazing! I tried the same file that gave the results above and tinyPNG got it down to 6k with no noticeable difference
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BatVink
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Posted: 17th Feb 2016 13:37
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Quote: "Or try this...

https://tinypng.com/"


Nice, added to my bookmarks!
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Markus
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Posted: 17th Feb 2016 14:50 Edited at: 17th Feb 2016 14:52
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Quote: "Advanced lossy compression"

if you have the original image its no problem.
normal the png is without loss at save, that was the advantage in compare with jpg.
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Phaelax
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Posted: 18th Feb 2016 20:47
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Quote: "24-bit PNG files can be converted to much smaller 8-bit indexed color images"


One would safely assume there would possibly be significant quality lost.

"I like offending people, because I think people who get offended should be offended." - Linus Torvalds
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BatVink
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Posted: 19th Feb 2016 09:14 Edited at: 19th Feb 2016 09:15
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Hopefully it is configurable, but this looks pretty damn good to me...

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Quidquid latine dictum sit, altum sonatur
TutCity is being rebuilt
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JohnnyMeek
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Posted: 19th Feb 2016 09:31
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There are a few of these online, plus there's a free plugin for photoshop.

http://www.fnordware.com/superpng/
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Scraggle
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Posted: 19th Feb 2016 09:38 Edited at: 19th Feb 2016 10:55
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The only issue I have come up with so far when using tinyPNG (and it is a TINY issue) is that monochrome images don't stay monochrome.
They are very close and not visible noticeable but not quite spot on.

The only reason I noticed is because I've created an image compression and encryption algorithm and it scans the image first to see if it has colour pixels or just a single colour image (think bitmap fonts) if it is just a single colour image then it can use a more efficient algorithm that discards all colour information and just processes the alpha channel.

If I use tinyPNG on a file first and then run it through my compression/encryption function it always selects the full colour option.

Like I said, it is a tiny issue and one that won't affect many users but it's worthy of pointing out.
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Digital Awakening
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Posted: 19th Feb 2016 15:26
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Regarding how many bits you should use for PNGs. 8 bit is fine as long as you don't need a better alpha channel and your image doesn't contain too may colors or gradients. You only get 256 colors or 255 + transparent pixels. 24 bit with transparency is usually the better option if you want smooth edges, because you get much better alpha information. 32 bit and 24 bit without transparency is however completely lossless.
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