Best way to down size images for IIS

[PKay]

This one comes up a lot.

I will give my take on it, please feel free to add your thoughts.

A good one for our famous moderator :)

If you look down in the deep space section, the reduced images are mostly JPEG.
Some random examples:
JPEG 167.4kB , 1024 x 632
JPEG 191.5kB, 1387 x 1181


The download page that comes up says the max. file size is 200kb.

I have found that it will accept up to 2Mb, but will then scale down your image to 200kb.

After downsizing an image (using the 'save as JPEG' function) I will open it with a previewer and check the files size and resolution.

So all that means if you get your image below 2MB (in JPEG), your good to go.

[JA]

Hello Peter,

For me that would beg the question of whether it is better to downsize the image yourself OR have the website (IIS in this case) downsize the image for you. I suppose there is no substitute for a back to back test with one's own image; however, here is some suggestion that it might be best to do it yourself (atleast on Facebook FOR COVERPHOTOS)......

https://photography.tutsplus.com/tutorials/facebook-jpeg-compression-how-to-get-the-best-image-quality-on-your-timeline--cms-23043

In this example one can see increased JPEG artifacting around the bird for COVERPHOTO IMAGES (Not Timeline images) images down-sampled from larger masters. It was also suggested as best to select "Save for Web" .Best to try a back to back test and see.

Best
JA

[jenchris]

It's why I seldom post pics.
I hate seeing decent photos macerated.

[leon]

I know what you are saying, however I usually take them to Photo Shop, (it is not the top version by the way) and then use image size on any image i wish to reduce, plus all the others one at a time.

Type in 800 on the wide side the rest is looked after, go to the left of screen to file, top left, and save for web, and your image will be reduced uniformly.

Save to your designated file and there you have it, one can also tweak it a bit to get it to the maximum just under 200kb's

Works really good for me :)

Leon :thumbsup:

[Merlin66]

Easy.
I use Irfanview to resize images and generally to provide a "quick" view of image files (including fits).
http://www.irfanview.com/

Highly recommended.

[muletopia]

In my thread below I posted small images which are not too degraded.
The first image started out at 87.2 MB. Irfanview made a terrible mess of it.

The posted image was reduced with the resize option in plain old Paint on Windows.
The posted image can be enlarged to view with control+.

Chris

[Allan_L]

For quick simple seamless integration I use...
FREE Download Image Resizer for Windows 10.

once installed it forms part of the right click drop down.

Right click on image file, select Image Resizer.
Enter required size parameters, etc.
Save or save copy.
Its nothing fancy, but quick and easy.

sorry can't recall from where downloaded
Just checking
I think its a newer version than the one I am using, but seems to be available from Microsoft Store.

Hope this helps

[PKay]

Oh dear, a can of worms is appearing!

It might seem that different processing software treats differing formats differently (I hope that makes sense).

So, back to basics.

I look at the images below (deep space), don't we all?
Those guys & girls know what they are doing :)

There seems a common theme...

Pixinsight and Photoshop.

Added: DSS, Auto Stakkert & Registax can be added to the mix.

And what ever works for you (covering bases) :-)

[raymo]

JA, It doesn't work for me. If I attempt to post to IIS any image over about 200.5kb it just keeps apparently downloading for a minute or two, and
finally stops, and tells me the file was too large.
raymo

[JA]

testing ....

1st image (DSC_5796ed50) was 1.96MB when uploaded and became 199KB with IIS resizing

2nd Image (DSC_5796ed12) was 186KB when uploaded and remained that size

They are almost the same finished size (199kB v 186kB), so the question really is: when enlarged to the same size on screen is there any quality difference? Unfortunately I can't get the on-screen enlargement function (Control +) to work differentially on these images on twin screens for a quick answer! Grrrrr! I will have to download them and recomposit something to check.

Best
JA

[raymo]

Perhaps its a recently introduced function; I'll have to try it as well.
This M4 was 1.78Mb.
raymo

P.S. Well, it did it, but the image is huge, have to take screen down to 33% to view it at right size.

[Merlin66]

Hmmmm
I still find changing image size to a jpg in Irfanview seems to work for me.

[JA]

I can't speak for every bit of software, but getting IIS to resize the image in the above comparison is better, at least than using MS Paint, that I used for this quick peek. Much better !

Have a look see at this EXCERPT from the top left hand corner of my previously posted image above....

The original 1.96MB image uploaded and resized to 199kB by IIS is much better than the same 1.96MB image resized to 186kB in MS Paint and subsequently uploaded to IIS (of course when viewed at the same on-screen size, which I've ensured here by compositing this sample image). I'm sure this won't be the case with all resize software (esp, if choosing "resize for web options", which isn't an option in MS Paint), but an interesting result nonetheless.


Best
JA

[kinetic]

Animation GIFs are a pain.
Only a 5 frame GIF that has been severely cropped fits under 200kB

Steve

[PKay]

Good tip Ken.
Have downloaded and tested Irfanview.

Started with a 6M jpeg file, and reduced it to 1.4M.
Up loaded the image (Omega Centauri) and compared with original.

It works a treat, so the thumbs up from me.

Good testing JA. Proves the 'down scaling' done on the server works for jpeg.