In this post, I attached this file. It was a .png on my computer. It was changed to .jpg, apparently by the forum software. Was this done to minimize file size? I see that my original .png file was about 3 times the size of the posted .jpg.
No problem, I just hadn't seen this before.

 

Yep, it does that sometimes, though usually it is a .gif. .gif is my prefered format.

 

Cool feature!

However, I think under conditions a .png can be smaller. I haven't found which ones though.

 

Cool feature!

However, I think under conditions a .png can be smaller. I haven't found which ones though.

.PNG can be reduced to 8bit or even less.
24bit .PNGs are quite large.

Some web site scripts inflate 8bit PNG to 24bit- they sometimes become unreasonably large.

 

I have also had my very clear PNG file changed to a fuzzy JPG file by the software in this forum.

 

Hello,

I am using the .png image format for posting schematics.
I am reducing the colors to 8 Bits deep, to reduce its size.
The 24 Bits .png files can get converted to .jpg, to reduce space.

Bertus

 

I am reducing the colors to 8 Bits deep, to reduce its size.

Bertus

How do you do that?

 

Hello,

I am using open Suse linux.
http://en.opensuse.org/Welcome_to_openSUSE.org
In there you have KolourPaint.
http://kolourpaint.sourceforge.net/
In the save as dialog, you can choose the colour depth (here is choosen for 256 kleuren (=colors)).

This image has the reduced number of colours.

The image editing program The Gimp Also has a dialog for reducing the size of .png files:

The Gimp is also available for Windows.
You can download The Gimp over here:
http://www.gimp.org/

Bertus

 

i am running Windows and using IrfanView as image browser/manipulator that supports many file formats. It handles file conversions, and various functions like crop, rotate, effects etc. It is light and fast and - free.

for test I used screenshot with particular display content and saved it as BMP (no compression) so I could use it as same input and generate different outputs:

test 1: GIF , size 149kb
this file format is pretty good for graph content like computer generated artwork (windows etc.).
small file size, no artefacts but colour degradation was easy to see because GIF only supports up to 8-bit colours. this file format was infamously used to extort royalties, after it was used royalty-free for years. that was the main reason it was abandoned. it was great for computer generated content (lines, frames, windows etc.). for nature (people, photography) JPG was much better but neither GIF not JPEG could solve all problems. there is an improved JPEG (extension JP2) but it is not free. then PNG came along and saved the day.

test 2: JPG, high quality (set as "100"), size 578kb
bearable file size, some color degradation and no significant compression artefacts other t.

test 3: JPG, med quality (set as "60"), size 166kb
reasonable file size but more compression artefacts and more colour degradation.

test 4: PNG, 24BPP (compression set to 0), size 3Mb
nice image but way too large file for forum attachments

test 5: PNG, 24BPP (compression set to recommended value 6), size 162kb
nice image, no observable artefacts or color loss, small file size
minute color loss can be seen only in direct comparison.

test 6: PNG, 8BPP with compression value 6, size 120kb
Menu: Image: Decrease Color Depth, 8BPP then save as PNG with compression value 6.
even smaller file but looks like GIF, color degradation while noticeable it is still less than that of GIF.

As shown, some experimenting can help determine optimum but I would say that leaving everything as is, and using recommended compression setting for PNG produces very good results.

 

I've been using MS Paint for so long that I've gotten good at it. (That means minimum time wasted looking for features and the quality is pretty good, etc.) Anyway, I've been saving as PNG and the file sizes are pretty small, probably because I only use black and white. MS Paint doesn't have setting options. Lucky me, huh? It works for stupid people

I see here that PNG's can be outrageously large, so, Mods: which "save as" does this site prefer? Whatever makes it fairly small?

 

Most nOObs post their first schematic as an extremely fuzzy Jpeg instead of as a very clear PNG.

I used an old PAINT program to make schematics for many years but now I have a new PAINT program that is completely different. I must learn it all over again.

 

I usually use .png to save computer generated images, such as MSPaint scribbles and schematics.
I leave photos in their original .jpeg format, but I reduce their size to 800x600 when uploading them for a more easy to use resolution.

I believe that the filesize might actually increase if one converts a real-life image from .jpeg to .png. I don't have proof, though.

 

Most nOObs post their first schematic as an extremely fuzzy Jpeg instead of as a very clear PNG.

I used an old PAINT program to make schematics for many years but now I have a new PAINT program that is completely different. I must learn it all over again.

Yeah, but the new Paint is WAY better than the old one, and the learning curve, for me, was not steep at all.

 

Hello,

The main difference between life photos and a drawing is the number and randomness of colors.

Bertus

 

Tsk, tsk... bertus, are you losing your edge?
http://en.wikipedia.org/wiki/Portable_Network_Graphics#Comparison_to_JPEG

 

Hello,

To read and convert graphic formats, you can use XnView:
http://www.xnview.com/en/index.html

It supports the following graphic formats:
http://www.xnview.com/en/formats.html

It is available for windows and a lot of other operating systems:
http://www.xnview.com/en/download.html

Bertus

 

That's more like you!