jpeg compression

[Dynasoft]

"It will compress better and won't lose any quality."
PNG loses quality, thats why its not a huge filesize, if it didnt lose quality it would be bitmap BMP. Like with MP3, it stores only what you can see and removes what the human eye cannot see

Being lossless, what it actually does is remove redundant data, for example replacing Blue,Blue,Blue,Blue,Blue by 5xBlue. It's still much smaller than a raw bitmap (.bmp).

There are lossless audio formats that do similar things, like FLAC, which is still far smaller than a raw wave (.wav) file.

[Anders]

Yes PNG is lossless (PNG-24)
The PNG-8 format is lossy though, it is very similar to GIF in many ways but can't have transparency in any way.

[aidmm]

I use PNG mostly because of it's ability to include a transparency layer (alpha channel)... I'm supposing that's the 24 bit version Andos is talking about (PNG-24).

[neat_Kliker2]

ah right, thought png was lossy ;s

[Sphax]

Yes, PNG is lossless data compression.

[HammerBro]

Yes PNG is lossless (PNG-24)
The PNG-8 format is lossy though, it is very similar to GIF in many ways but can't have transparency in any way.

I didn't discover the PNG-8 format until recently, but unless Photoshop hacked in the functionality (which doesn't seem like something Adobe would do), PNG-8 does support transparency, as demonstrated here. Right click on it and go to View Image for a change of background.
(Fun fact: That's a 4 color PNG-8 image. White, black, grey, and an offwhite I used as transparent. It is 156x232, losslessly compressed, and only 2.22KB. Because the image was too big, deviantART automatically created a thumbnail JPEG, which is lossily compressed but only 101x150. It's 4.27KB, though. The moral of the story? Small color palettes are our friends! And it's only lossy if the number of colors in the palette is less than the number of colors in the image.)

[Dynasoft]

Actually that's not the strict definition of lossy, being paletted doesn't make it lossy, though if the original image is true colour you will obviously lose some.

Essentially the most obvious difference is that a lossy compression format will have a quality slider in the compressor.

[Sphax]

Or a number of colors to choose.

[Dynasoft]

Or a number of colors to choose.

As I said, that makes it paletted, not lossy.

Example: If you load a jpeg (lossy) compressed at 50% quality, and save it at 75% quality, the picture will change slightly, actually reducing the quality. In fact most lossy compressors will cause the image to change even if you load and re-save it with the exact same compression options it was originally saved with.
If you load a paletted image (eg 4-colour png) and save it with more colours (eg 8) then it will look exactly the same.

Though I have just found a lossy PNG compressor: http://membled.com/work/apps/lossy_png/
Which outputs a standard PNG image, just not one identical to the image passed in.

[gamer4fun]

but, what type of image can i use to reduce mmf2 proccessing?

using both jpg or png it spend the same memory when running, using the Picture Object