JPEG versus PNG

gyroscope

Hi, I guess I should know this by now but anyway...

Each 1024 x 786 image I have is approx. 800KB. I use Save for Web in Photoshop, and save each one as 24bit PNG file, but these are 1.4MB in size, i.e almost twice the size. I always thought that PNG had some sort of nifty compression algorythm included so that they were even smaller than JPEGs, not larger. Any /info on this topic – or advice if I'm doing something wrong – appreciated, thanks.

Photics

As mentioned in The Unofficial GameSalad Textbook...

Use PNG

GameSalad doesn't care if it's jpeg, gif, tiff, it's just going to convert it to PNG.

RacetotheMoon

Seconded. Use *.PNG

Why are you using save for web?

gyroscope

Thanks guys; sure I understand that I should be using PNG, I'm just a bit confused by the fact that the file size is almost twice the size of JPG. I always thought they were smaller. I guess that's just the way it is... Could you confirm that I save the 24bit version of PNG please?

AkioAkemi said:

Why are you using save for web?

I used to bung in the JPG files into GS for it to convert automatically for me, but the size comes in at something like 1023.99 by 785.9. This is due to saving the thumnail, I think. It was Joe (firemaplegames) who suggested using save for web. This way the discrepency is avoided, and the image comes into GS exactly right, i.e 1024 x 786.

PS I keep meaning to buy copy of your The Unofficial GameSalad Textbook, Photics, but I'm a bit short of dosh at the moment. But I will... :-)

inception

PNG vs JPEG

Stormtrix

google PNGCrusher this will help compress your .png files a little smaller as well.
Sometimes on large pics cutting them in half for size.

I also use the save for web feature in PS

gyroscope

Thanks all. And cheers Stromtrix; I'll checkout PNGCrusher.

:-)

dotsonj23

Why use save for web rather than save as. Is there an advantage?

sebmacfly

Better using PNG, because you can use transparency! (you can't do that saving your file as jpeg)

gyroscope

That's true, sebmacfly, thanks.

Dotson123: have a read of my second post in this thread; that explains it! :-)

gyroscope

Hang on, just had a thought: if my backgrounds don't need any transparency, then I could use JPG, at almost half the file size of PNG? Could anyone confirm this please?

netdzynr

Both JPEG and PNG are compressed image formats. And JPEG is "lossy" (not lousy), which means some of your image data is lost when saved. Even if you could use JPEG and save a bit on filesize, both formats need to be decompressed when displayed, so neither will save more than the other in terms of memory use.

gyroscope

Understood, thanks for that netdzynr. :-)