WEBP Export questions

[Pšenda]

9 minutes ago, DarkClown said:

How can lossless compression be about "image quality"?? I can undestand that it may be about compression speed and file size - but not "image quality". If that's the case "lossless" is the completely wrong term!

Excuse me, but did you read my post? What is incomprehensible about the sentence "Which is of course directly related to image quality, and at the same time related to compressed file size and compression/decompression speed"?
It is perhaps understandable that in some cases of "compression quality" the context with image quality ceases to be decisive - because the maximum has already been reached, but other factors (size and speed) start to prevail.

[DarkClown]

3 minutes ago, Pšenda said:

Excuse me, but did you read my post? What is incomprehensible about the sentence

Of course I did. And there is nothing incomprehensible  - it's just wrong from my perspective. A lossless format is NEVER about image quality! (That's why it's called "lossless"). What you write is correct for lossy formats.

[Pšenda]

2 minutes ago, DarkClown said:

A lossless format is NEVER about image quality!

Why not?!! After all, it is about the highest possible image quality!

[walt.farrell]

7 hours ago, carl123 said:

And none of the default preset dropdown options for Lossless actually activate the Lossless checkbox.

That's just been reported as a bug. But with an analysis that shows the checkbox is active, just not displaying properly.

 

[v_kyr]

Better show the cwebp manpage ...

• cwebp - Man Page

Quote

-lossless

Encode the image without any loss. For images with fully transparent area, the invisible pixel values (R/G/B or Y/U/V) will be preserved only if the -exact option is used.

-near_lossless int

Specify the level of near-lossless image preprocessing. This option adjusts pixel values to help compressibility, but has minimal impact on the visual quality. It triggers lossless compression mode automatically. The range is 0 (maximum preprocessing) to 100 (no preprocessing, the default). The typical value is around 60. Note that lossy with -q 100 can at times yield better results.

-q float

Specify the compression factor for RGB channels between 0 and 100. The default is 75.
In case of lossy compression (default), a small factor produces a smaller file with lower quality. Best quality is achieved by using a value of 100.
In case of lossless compression (specified by the -lossless option), a small factor enables faster compression speed, but produces a larger file. Maximum compression is achieved by using a value of 100.

...

Examples

cwebp -q 50 -lossless picture.png -o picture_lossless.webp
cwebp -q 70 picture_with_alpha.png -o picture_with_alpha.webp

... as one already can see there, the "-q float" option specifies the compression factor for RGB channels between 0 and 100. The default is 75.
In case of lossy compression (the default), a small factor produces a smaller file with lower quality. Best quality is achieved by using a value of 100.

In case of lossless compression (specified by the -lossless option), a small factor enables faster compression speed, but produces a larger file. Maximum compression is achieved by using a value of 100.

As an lossless example call:    cwebp -q 50 -lossless picture.png -o picture_lossless.webp

[DarkClown]

13 hours ago, walt.farrell said:

That's just been reported as a bug. But with an analysis that shows the checkbox is active, just not displaying properly.

I assume that's the same issue I mentioned earlier (the two "lossless" checkboxes seem to behave different)

I just wonder: if the "lossless" checkbox and the "Quality" slider do exactly the same - why are they duplicated? Or does the functionality of these two elements differ in the "Files Settings" and "Advanced" sections?

[Pšenda]

10 hours ago, DarkClown said:

if the "lossless" checkbox and the "Quality" slider do exactly the same - why are they duplicated?

??? But they don't do the same thing! You seem to be missing, or not understanding, the previous posts where this has already been explained.

Try again to pay attention to the previous information, from which it is explicitly clear that these are two different/independent parameters for controlling the compression algorithm.

[DarkClown]

1 hour ago, Pšenda said:

??? But they don't do the same thing! You seem to be missing, or not understanding, the previous posts where this has already been explained.

Try again to pay attention to the previous information, from which it is explicitly clear that these are two different/independent parameters for controlling the compression algorithm.

Thank you for your valuable input ... as before I was already further down the road. I think by now (di a bit of reading in between) I've got a pretty good understanding of the available options and the functionality of each of them. But since you do not seem to get my point I guess I was unclear or unprecise. My apologies for that. Here again my point in a more visual way:

Red arroww settings are identical / green arrow settings are identical (or maybe not - that was my question) Why would you have identical sliders in the same dialog?
Just take your time to understand what I am referring to.

[walt.farrell]

You're not using a Preset, @DarkClown, so we can't be sure what the Lossless checkbox indicates just from that screenshot. If you click Lossless, so you can see the check mark, does the estimated file size change?

[DarkClown]

46 minutes ago, walt.farrell said:

You're not using a Preset, @DarkClown, so we can't be sure what the Lossless checkbox indicates just from that screenshot. If you click Lossless, so you can see the check mark, does the estimated file size change?

Hi Walt,

if you are referring to my above screenshot: that wasn't about the file size. It was purely about two parameters ("Quality" slider and "Lossless" checkbox). Each one appearing 2 times in the same dialog - displaying identical information and seem to be synchonised.

In terms of files size: When I select lossless file size hardly varies at all (19.13MB at 100% Quality vs 19.16MB at 0% Quality) while lossless being unchecked I get 196KB at 0% Quality and 6.37MB at 100% Quality.

Still one would expect lossy compression with 100% quality being "lossless" - but it is a huge filse size difference. What would mean 100% quality is still quite "lossy" ... The wording (and different algorithms) makes it slightly complicated I guess.

[walt.farrell]

14 minutes ago, DarkClown said:

Still one would expect lossy compression with 100% quality being "lossless"

 It isn't for JPG, so I'm not surprised if it isn't for WebP, either.

[DarkClown]

5 minutes ago, walt.farrell said:

 It isn't for JPG, so I'm not surprised if it isn't for WebP, either.

True - aside the fact that there is a real lossless version of JPEG available but seldom used (https://en.wikipedia.org/wiki/Lossless_JPEG)

[carl123]

1 hour ago, DarkClown said:

Red arroww settings are identical / green arrow settings are identical (or maybe not - that was my question) Why would you have identical sliders in the same dialog?

Firstly, this is not unique to WebP, you will also find duplicated options in JPG, EPS etc

Now if you look in the Advance section you will see that it can have the same or additional options or some missing options from the File Settings section (such as Size and Area). You will also notice that the Hamberger menu is for the Advanced section, which means when you create a Preset it is based on the settings shown in the Advanced section.

So, by duplicating the options, that will be part of the Preset, you immediately see what that Preset will contain and the specific values

[Pšenda]

3 hours ago, DarkClown said:

But since you do not seem to get my point I guess I was unclear or unprecise.

The problem is that you asked "two" questions - as a reminder:

14 hours ago, DarkClown said:

I just wonder: if the "lossless" checkbox and the "Quality" slider do exactly the same - why are they duplicated? Or does the functionality of these two elements differ in the "Files Settings" and "Advanced" sections?

The first question (only this I responded to it) "if the "lossless" checkbox and the "Quality" slider do exactly the same - why are they duplicated?". I assume that it is clear that these two parameters (controlled by the checkbox + slider) are not the same, and thus are not duplicated.

The second question "Or does the functionality of these two elements differ in the "Files Settings" and "Advanced" sections?", is about a completely different issue (note your wording of "Or" at the beginning of the question), and that's why I didn't respond to her - not related to the compression quality discussion. 

[R C-R]

5 hours ago, Pšenda said:

Try again to pay attention to the previous information, from which it is explicitly clear that these are two different/independent parameters for controlling the compression algorithm.

My takeaway from that is "compression factor," which has a range of 0 to 100, is what in Affinity is called "Quality," but is it really that simple?

BTW, on my Mac, when I click on "Quality" in the Advanced section to open the slider I get a system error beep when I move it, although it does change the value. Anybody else using a Mac seeing the same thing?

[DarkClown]

56 minutes ago, Pšenda said:

The problem is that you asked "two" questions - as a reminder:

As I said - my mistake, I was unprecise.

[R C-R]

16 minutes ago, LondonSquirrel said:

Also why is it a slider under File Settings, but a drop down -> slider under Advanced?

There does not seem to be any good reason for that because at least on my Mac there is a lot of empty space at the bottom of the export window for the slider to appear in the Advanced section without having to click on Quality to reveal it.

[DarkClown]

2 hours ago, carl123 said:

Firstly, this is not unique to WebP, you will also find duplicated options in JPG, EPS etc

True - but that does not make it better

2 hours ago, carl123 said:

Now if you look in the Advance section you will see that it can have the same or additional options or some missing options from the File Settings section (such as Size and Area). You will also notice that the Hamberger menu is for the Advanced section, which means when you create a Preset it is based on the settings shown in the Advanced section.

So, by duplicating the options, that will be part of the Preset, you immediately see what that Preset will contain and the specific values

I get your point. But frankly spoken - why does the "File Setting" section exist in the first place if all the features are covered in the advanced section anyhow?

On the other side it's a design/layout topic not worth making this a big discussion. Important features are there. And it's not related to my major point of criticism: that file dimensions are not covered by the presets. As well I still don't get the ICC profile topic (maybe a feature I have not discovered yer or a bug)

[R C-R]

1 minute ago, DarkClown said:

But frankly spoken - why does the "File Setting" section exist in the first place if all the features are covered in the advanced section anyhow?

Because they are not all also there in the Advanced section. The Size, Presets, & the Area items, plus the 'don't export hidden layers' checkbox are only in the File Settings section.

The only items in both are the Resample options & the "Quality" adjustment.

[DarkClown]

Any reason the dialog doesn't look like this - beeing half as confusing?

[R C-R]

3 minutes ago, DarkClown said:

Any reason the dialog doesn't look like this - beeing half as confusing?

None that I can think of, except that maybe that it might seem to be a confusing inconsistency for some users if everything in File Settings & Advanced was combined into one section for WEPB but not for some of the other export formats where there are lots more Advanced options, like for PDF.

[v_kyr]

4 hours ago, DarkClown said:

Any reason the dialog doesn't look like this - beeing half as confusing?

When looking over the "libwebp" documentation, specifically the encoding APIs there (aka the simple encoding API and the advanced encoding API), so their WebPConfig structure and different encoding functions ...

• libwebp API documentation (en)
• libwebp API documentation (de)

... I think the Affinity devs tried to map those to their common default & advanced (more) panels export option settings, as they did for other image file formats too.

However, I've the impression that the WebP encoding/export generation UI is a quickly made (last minute) one and so might be reworked and better optimized in future update versions. Also the fact, that the online help misses to tell anything valuable about the WebP export format option settings (see here, and there then below also "Settings unique to WEBP format") indicates that to me!

 

[DarkClown]

2 hours ago, v_kyr said:

I think the Affinity devs tried to map those to their common default & advanced (more) panels export option settings, as they did for other image file formats too.

I guess you are right with this assumption. Nevertheless I'd like to challenge this approach, since (unlike from a programmers standpoint) it does not make a lot of sense from a users perspective. First of all trying to make the "export" feature the same for all formats does't reflect the individual needs for each of the formats. And a questionable implementation doesn't get better by implementing it for all export formats. It certainly doesn't reflect the workflow requirements of many users ... it's a plausible - but nerdy aproach, not taking usres workflow into account. 

And again - not worth disussing - considering the far more relevant mishabs and possible improvents that could be implemented.

I actually appreciated you constructive technical input (and links) in this discussion!

[v_kyr]

1 hour ago, DarkClown said:

Nevertheless I'd like to challenge this approach, since (unlike from a programmers standpoint) it does not make a lot of sense from a users perspective. First of all trying to make the "export" feature the same for all formats does't reflect the individual needs for each of the formats. And a questionable implementation doesn't get better by implementing it for all export formats. It certainly doesn't reflect the workflow requirements of many users ... it's a plausible - but nerdy aproach, not taking usres workflow into account. 

Well the previous said is just my personal guess of course, there may also have been completely different reasons why the export options were implemented in this way in terms of the UI (as for example considering and honoring preset handling, doc color management and the like).

However, you can compare with other graphics tools how export panels for the webp format look in contrast there then. - Here for example in GC ...

 

[DarkClown]

On 12/18/2022 at 4:17 AM, carl123 said:

The preset is still there after a restart, you just need to reselect it for that session

Of course the saved preset is still there after a restart. But the selection is never remembered. Not even in the same session for the same picture. You need to re-select presets (that do not even cover essential parameters) for EVERY picture you work with - even if you did not close the program. Parameters that are not covered in presets (e.g. dimensions) obviously need to be re-entered in the same session over and over again.
(No I won't start a rant - I guess the degree of "usability" is obvious) Just imagine having to export 100 WEBP pictures for a client in 1400x800 resolution. For each picture you have to re-enter 1400x800px dimension, choose the same (pre-made) preset, select "Selection area", click on "Include bleed" and choose an ICC profile befor you can export the picture with another click. Considering this all could have been covered by a One-click with a thought through export receipe...