when we save a photo as PNG should we interlace or non?

I don't know in the specific case of a PNG, but generally interlacing refers to reducing the quality of an image to make the file size smaller.

actually .. interlacing means that when the image loads to the screen for a viewer to see it (over the internet) .. it loads every other scan line (pixel line) .. so that a viewer of the image or a web page using PNGs will see results sooner ..

the image will look ODD at first and then resolve to a solid final image over time .. depending on how many passes you told it to take .. 4 passes, for example

JPEG has the same deal, called "progressive"


I have always chosen to skip it .. just personal preference, really .. being a dial upper I don't like to figure out if it's done yet

so option none is the one, right! that's what i've been doing. thanks for your other comments today!

of course .. I may have mixed my metaphors ..

Progressive JPEG asks you for a number of "scans" .. PNG does not ...

but, until I'm corrected, that's my story and I'm stickin' to it

I upload in PNG and go 'none'. I have tried auto but didn't see any difference so I just stay with none because I know it works.

thanks, everyone!

That's it? Thanks everyone? What...no party?

GIMP is particularly good at compressing PNGs. PNGs have lossless compression, so the better the compression, the less useless information in your picture.

You mean the beer cans and other garbage will disappear?

PNGS are not compressed as such so saying GIMP compresses PNG well is a bit of a misnomer...or is that just me? as far as am I aware - the only possible variations in PNG are bit depth (irrelevant here as the server only seams to accept 8bit) and interlaced or non interlaced. Other than that - the PNG parameters should be exactly the same regardless of the application that created them.

Images saved in PNG format are indeed compressed; the difference with regard to JPEG is that PNG uses a lossless compression scheme that doesn't fiddle with any of the original image content. It uses logical compression similar to the way ZIP format archives compress your generic files (no information is lost due to the compression). If you have trouble understanding how such lossless compression of information is possible then consider an example of two images: a photo of a dog and a solid red background. If both images are the same pixel size then both will be stored in the exact same file size if saved as a Bitmap (because Bitmap images simply store the image by recording each pixel color individually and use no compression). However, an image format that uses compression can store the red image in a smaller file by simply saying "every pixel is red", but this is not as easy to do with the dog photo. Therefore we would expect the red image to be stored in a smaller file than the photo. The compression rate that can be achieved is related closely to the concept of Entropy.

sorry for the misunderstanding of my post - I meant that it didnt compress as in the traditional perception of image compression by removing physical data and reconstituting it as in JPEG.

so in lay terms, PNG is fresh squeezed, and JPEG is from concentrate...?

*edit - that was a joke..

No .. (*shakes head*) .. PNG is "tastes great" .. JPG is "less filling"

Being a QLD'er, I live quite close, geographically, to PNG.

I have no idea where JPG is though. But I use my JPEG's to hang my JWASHING on the JLINE.

you do know the J is copywritten for me.. lol.. let me see how much you owe me for using all my J merchandise... lol

Ca - ching !! Says Jackie all the way to the bank.

Sam means Poo Poo New Ginny.

u know what sucks?

i did a design for a band banquet program cover.
i saved it in PNG, and took it to kinko's...

THE BLOODY IDIOTS COULDN"T OPEN IT!

Try saving it in BMP format for that..

I'm not exactly a member of the "Geek Squad" so bear with me. I've been away from Caedes for a while and couldn't wait to post again. I noticed upon uploading it's now recommended to do so in PNG format. No problem I converted my jpg to PNG and uploaded without a hitch. My question concerns the difference in bits. PNG on my computer shows an extreme difference in bit count. Megabytes vs Kilobytes. I'm wondering if the Caedes server reverses the process once uploaded. ( Which seems to me would negate the purpose for PNG in the first place ) If not the storage space would be considerably different ... and at the rate pics come in everyday ... well you see what I'm getting at ... McGees closet in no time at all. Uh ... forgot my age ... "McGees closet" probably means nothing to you youngsters.

ok - the general idea is JPEG is a pretty crude compression system that degrades your image data every time you re-save it - even at max setting. Jpeg 2000 sorts a lot of that out and PNG is pretty much the same scenario. yes, there is some compression involved but not in the destructive sense. the Caedes server recompresses data when it creates new versions of images so starting out with a relatively undamaged original works best.

Thanks Phil ... I think I've got it straight. I had mental images of the Caedes server bursting at the seams in no time at all.

McGees Closet = McGeri's Closet ??


what'd I win??

John: the best is to set your cam with an uncompressed format (raw or tiff), then to save your postproccessed photos in PNG without saving them in JPG between the two processes