Mike Chaney's Tech Corner

When we resize for Web is sophisticated QImage maths involved?

In other words does QImage create technically better web size images?

As I see it reducing a 3354 wide image down to 1024 something must be lost, and I wonder if different programs give differing quality.

I have just done a quick comparison with QU and there is a considerable degrading, partly no due doubt to going from a monitor custom profile to sRGB (I always keep jpeg at 100pc)

and what happens if recipient resizes it down again to 800 x 600 and re saves?

Jeff   

Hi Jeff,
Yes, the same algorithm is used and in addition, users have control over anti-aliasing in the Interpolation dialogue. This is because some subjects like roofs with tiles can produce a strange pattern so an increased level of anti aliasing is required. Too much can soften the image.
Yes, a lot of pixels are lost but the way it is done should be superior in QU. The quality differences are usually less obvious in downsizing the the anti-aliasing can be significant I think.
But a downsized image is not expected to look as good as the original but should be reasonable when viewed at it's smaller on-screen size. The colours of an sRGB image will be subdued when compared to an Adobe RGB or a camera profile image but it is still best to view with a colour management aware application. For Web browsing, Firefox is colour management aware providing the profile is embedded. However, it only seems to work with Adobe RGB and sRGB.
Quality will be lost, not so much from downsizing again but by the fact of re-saving a jpeg. I don't really know how noticeable this will be but 1 extra save should not be significant on such a small image.
Terry
PS.
What exactly do you mean by this?
I wondered too what prompted your questions.
T

I double-downsized an image once using Qimage.  Degradation was obvious even when viewed on-screen.  I no longer recall details like image size or quality settings.  But I went back to the original image and downsized it in one step.  Much better quality.

This is very important to quality: Quality setting should be 90+ if you are looking for quality. It is the amount of compression vs file size.

Fred

Yep.  I just remembered that a couple of times when I was in a hurry, I downsized without bumping up the quality settings.  Makes a difference, no doubt.

I did a quick web size copy with QU and then conpaired side by side with the orig.  Quite a difference.

The question was prompted by there being a difference in the image quality on local camera club web site when compared with memory of original print or projection at club competitions etc.  There are images on club site by me, QU created and they look a better quality than some by other members.

The club insists on submitted images being 1024 x 768 @ 72dpi (leaving aside the 72dpi) I found out that the WebMaster reduces the 1024 x 768 down to 800 x 600 and resaves, this is to comply with max image size allowed by web hosting site.

I asked why they do not have the images submitted in 800 x 600 and got a blank look, I further pointed out that as far as I am aware it is not good practice to keep resaving jpeg on jpeg and got another blank look.

So I just thought I would ask if QU does a better web quality that other progs. (I don't think the current WebMaster is using PS.)



Just for you to have a laugh I copy below the club instructions for creating a Web size image.


''IMAGE SIZE
TO RESIZE IMAGES FOR DIGITAL PROJECTION IN COMPETITIONS

1. OPEN IMAGE IN PHOTOSHOP Flatten any layers (duplicate if wanted later)

2. From task bar click on IMAGE

3. From drop down menu for MODE check that RGB and 8 Bits Channel are ticked.

4. From same menu click on IMAGE SIZE.
In Image Size box
(a) Make sure that Resample Image is ticked
(b) Change Resolution to 72 p.p.i.
(c) Change largest Pixel Dimensions (may be Width or Height) to 1024 pixels
(d) If the Shorter dimension is now more than 768 change to 768 pixels.
Note: the longer side will now be less than 1024 (this is correct)
Example: With a square format image the end size will be 768 X 768

5. From FILE Select SAVE AS
In Save as Box
(a) File name: Type in the Exact Title you wish to give your entry.
(b) Format: From drop down menu select Jpeg
(c) Save In: (Top of Box) From drop down List choose Location of choice

6. Finally click on SAVE (bottom right of box)

This will save your image to a location (and folder) ready to Email or copy to a Disk for digital projection in the  Digital Competitions.
This leaves your original (photoshop) Image unaltered in its original location, provided you click NO when asked if you wish to save changes to your original image, when closing down.

QUICK METHOD To crop any part of your image down to 1024 X 768 pixels.

1. Open Image in Photoshop

2. Select Crop Tool

3. Change settings on Task Bar to Width 1024 px Height 768 px Resolution 72
Important that you type ‘px’ after the size. (Resolution is default at pixels per Inch)
You can toggle between 1024 for Width or Height in the Task Bar.

4. Crop area of your choice. (it can be as small an area as you wish) and it will always be 1024px X768px and 72ppi.

5. and 6. as above.

Please use the same method and sizes for submissions to the WEB (Web Master will resize down and save for the web). Send by email or disk to the Webmaster:  address and email can be found in the Programme issued to all members.''

Compare that lot with QU method.

Jeff

Jeff,
I think there's a feature in Qimage that might have escaped you.
With regard to the above, Qimage will keep the 1024 size even if the image is rotated so the first dimension is 768.

Let me do this by example. Then you can experiment with your own images.

I have a cropped image of a bird. Its resolution is 1623 x 2027.

Notice the first dimension, the horizontal one, is the smaller one.   
If I tell Qimage, or other software to make a 1024 x 768, I will get 615 x 768.  (As you described)
But Qimage has a little trick up it's sleeve....

If you right click on the image in the preview panel (right side of screen), and select make email web sized copies, as you normally would, and click 1024 x 768 as you normally would, now simply change the right side resolution in the text box so the requested resolution is 1024 x  1024.

Now, when you want a 1024 x 768 you will get it (as close as the aspect ratio will allow)
I leave mine that way all the time.

See screen snaps, please!
The first one shows the results of asking for 1024 x 768 with a portrait image  You can see 615 x 768
The second is the same image using 1024 1024.  You get 820 x 1024.

Just a trick that you can use even when just emailing pictures to royalty.

Fred

Good one, Fred, thank you!  I had indeed overlooked this technique, and I'll certainly be able to make use of it in the future.

If my thinking is correct--and I'm basing my thinking on your example--your method DOUBLES the choices in the QI menu when downsizing images...or allows some "fine tuning" of the downsized image dimensions, so to speak.

This is not something to which I've given a great deal of thought.  But I do remember many times making email/web size copies when I just had the vague feeling that I ought to have more choices than were in the drop-down menu.  I was right!  I DO have more choices.

Thanks for tip Fred

Next time if fire up QU I will certainly check suggestions.

Jeff

Wow Jeff!  The above sounds like the royal brush off!


... and Owen,
to reply to your thoughts, I would have to say, broadly, yes, you can fine tune your size, but always remember, the aspect ratio (ratio of horizontal to vertical) rules.
In other words, you can file tune one size, and the other side will take care of itself depending on aspect ratio.
By setting both sides the same, you assure yourself that one side will be the the requested size, and the other side will be as big as it can go, constrained my the aspect ratio.

There are two distinct places to use to create e-mail web size copies. That is what you are probably remembering.

 A right click on a thumbnail of a selected image and a click on Make email/web size copies, will provide a somewhat different set of options.

I use this a lot when Terry and I share images and the filters we made.

Hope I didn't muddy the water too much!

Fred

Yep.  That's what I like, even when I'm simply choosing from the pre-set sizes in the drop-down box.  Easy-peasey.  Downsizing in other programs (like in the example Jeff posted) is like jumping through hoops.

Don't know just what you mean by royal brush off, but then I have spent this morning and half afternoon concreting in a fancy post, wooden/steel post that is, not a forum post.  I am about knackered. :(

Any way got royal permission to fire up QU and checked tip.

I don't think I have used that method.  If I have well it's craft moments again.

Thanks

Jeff

Again.

Checked web size against sns hdr .tiff original.  Quite a difference.

jeff

Jeff,
You have to understand that knackered is not a word we hear on this side of the pond.
Could you, perhaps, put "Knackered" in some sort of level for us.?

Where would it fit; between what numbers?

1) Getting tired

2) Need a break

3) Getting bushed

4) Flagged out

5) Fagged out

6) Exhausted

7) Pooped

8) Dog tired

9) Need a nap

10) Last time I do one of these!

11) I don't care what it costs. Call the repairman!

Please explain!  "Quite a difference between what and what?

Ah, yes...British usage and American usage...

In the mid-1960s, I spent two summers working for a general contractor in my home town.  He was a WWII vet who saw combat in Belgium, but spent much of his service time in England.  Early on, he was allowed a period of R & R and went to a London hotel.

After he checked in, the attractive young lady behind the desk handed him his key and asked, "And what time would you like to be knocked up in the morning?"

He had previously received advice that this hotel was a good place to stay, and momentarily took the young lady's comment as confirmation of that advice.

He ultimately returned to the states with a British bride, so evidently the language barrier was not insurmountable.

Jeff,
I did some macro shots about an hour ago and sent a 1024 pixel image to Fred.
See attached below, a screen shot from QU comparator: - 1024 px jpeg on the left, the raw image on the right. The 1024 jpeg is zoomed in 1 click and the raw was zoomed out to get the on-screen size as close as possible.
Except for the resolution differences, and  a little colour error due the monitor profile in the screen capture, there's no real difference.
Terry

PS. corrected, the 1024 px was not zoomed in with the comparator.

and here is the same jpeg screen image corrected for monitor profile and re-saved at 80%.
Spot the difference other than colour?
Terry

Judging by your posts and the screen snaps, it seems like you are telling Jeff to stop "Bugging" you.    :-)
 ;D :D ;) :)

No, I just want to understand what the problem is; I wonder if something is going on that we are not aware of which is causing Jeff's downs-sized images to be degraded.
Terry

14568

It would make a good password :)

Knackered is a saying from the time of working horses.

When they were old and passed it they were sent to the Knackers Yard.  A place where knackered horses were dispatched.

I will post my before and after when I 'next fire up QU' but the tiff will be many megs.  Will see about posting on Zenfolio.

Out for the rest of day on orders of SWMBO

Jeff

Jeff,
Perhaps you can tell SWMBO (She who must be obeyed) that you are "knackered" and not have to go?

Seriously, getting back to the "degrading" question.
I have some settings to offer you.
I just did some experiments and posting is difficult because in order to fit the minuscule allowance of file size, I have to scrunch the screen snap.

The biggest difference in what seems to be quality degradation but is actually less sharpening, is the setting you choose in the Anti-Aliasing setting.
If you set that to low.... you are "golden"
Now, you can do 90% or 50% quality and can barely see the difference.

Terry touched on this earlier when he mentioned roof lines and certain line patterns that require a higher setting of Anti aliasing.
Set yours to LOW.

Snap 081 shows the setting I was talking about.
Snap 077 shows a Quality setting of 25%  (Pretty darn low and should compromise the quality
Snap 082 shows a Quality setting of 90%, and finally
Snap 078 is the Original Raw.

This shot is a beautiful image shot by Terry, so sharp and perfect that I want to smell the print.

What I am showing you is there is no degrading to be seen at all when downsizing using 90%, and even 25% (which is really an emergency extreme) is tolerable.

If you get poor results at your end, then you need to send me or/and Terry your original.
You have done it before... using WETRANSFER or YOUSENDIT, both free!

Fred

Thanks to you all for comments.

I have not previously messed about with the Anti aliasing settings, always been satisfied with default, but had a quick look yesterday morning and did notice differences.

Any way have now well and truly run out of time, and will have to investigate further in a week or so.  All next week I am as they say 'tied up'

Jeff 

Lucky man!!
Does your wife have the fuzzy handcuffs?

Here's an odd turn of events.
I shot this a few days ago, and was sending it to some friends when I couldn't believe my eyes!
Horrors!!

I had left the compression/quality setting on 25 from when I was trying to show the flowers in a previous post.

So, I had to redo it, but it does afford me a striking example to show how the image degrades.

Look at the blue sky....
One is 25 Quality and the other is 90

Easier to see than the flowers.

Fred

Jeff and others,
I took a photograph at the weekend that seemed ideal to show the differences with the Anti Alias settings. I've put them on Pbase and linked to this post below.
I chose this image particularly because of the roof tiles and the moire pattern that can occur. The original image is a 5202 x 3465 pixel CR2 image downsized to 900 pixels on the long side.
Anti Alias OFF                                                                                                                                                      Anti Alias HIGH
(http://www.pbase.com/tjm04/image/145977463/original.jpg) (http://www.pbase.com/tjm04/image/145977469/original.jpg)

Anti Alias LOW                                                                                                                                                      Anti Alias MED
(http://www.pbase.com/tjm04/image/145977467/original.jpg) (http://www.pbase.com/tjm04/image/145977468/original.jpg)

I normally use the Low setting but in this case, if the moire patterns bother you, the Medium setting is better.
Terry
PS. Jeff, you may know this place as it's in your county, Belton House near Grantham.  ;)

Thanks for the excellent examples.  Just getting back to the subject (been away to the Mosel area of Germany, a photographic disaster :))

I have seen moire patterns mainly on thumbnails and camera screen, they seem to be taken care of in the raw development.

I will be looking through my image stock to try to find some examples to mess about with.

I am told we have never been to Belton House, Burghley House some years ago but I cannot remember much about it.

Thanks again for your efforts

Jeff

H Jeff,
welcome home.
Thumbnails and screens require a big pixel size reduction and it's unlikely the downsizing is very sophisticated so it's not surprising moire patterns appear. As soon as you look at the full size image, raw or jpeg, they'll not usually be visible.
Terry