[KDPValidator] Validate epubs for KDP upload only

[slowsmile]

@DiapDealer...Thanks for that. What I must also do is remove all cover image file and cover image checks -- including the cover image format check and the cover position check as they will be redundant. And if the cover image file is there in the epub I'll just display a single warning as you've already advised.

You're suggestion for allowing plugin users to set prefs to quell warnings is also a good idea. At least that will allow users to get rid of warnings(like svg warnings) if they prefer. I'll put that in too, probably using json prefs rather than a dialog.

[jhowell]

It is only tangentially related to this plugin but I will mention this here because it may relevant to those interested in validating EPUBs for Kindle publication.

The latest version of the Kindle Previewer, 3.25, has some code to perform an image quality check and includes the OpenCV library for analyzing images. It appears to be a work in progress and I haven't found a way to actually enable this feature. Some new messages contained in the program include:

"File Validation failed: For details, please see Quality Report."

"Cover Image does not meet the image quality bar of 300 PPI."

"Cover image occupies 100% of the screen, therefore the image either needs to be greater than 1200 PX width or 1800 PX height."

"High Definition Visual Warnings (HDV) - These warnings are for images which does not meet high definition image bar of 300 PPI. We highly recommend fixing these issues to improve the quality of the book for the readers."

[Hitch]

Originally Posted by slowsmile

<snippage>

You're not wrong about the "works for me" part. But if you can point me to the detailed Kindle Guidelines for correctly formatting the Look Inside version of my ebook, I would be very grateful for that information. Unfortunately, the Kindle Guidelines gives no information at all on how to properly format the Look Inside version. That information should be in the Kindle Guidelines because it is important. Why isn't it there? So all I can do is try and find a successful way to do it for myself which is what I've done over the years. And if people think that my info is taking a bit of liberty and a load of bunk then that's fair enough. My only intention is to pass on some useful information to other authors/formatters that is not in the Kindle Guidelines. But really, the best person for you to ask whether the Kindle Guidelines is up to date and accurate is Hitch. She has also, on occasion, expressed some considerable frustration with info holes and lack of guideline updates in the KDP forum. So best to ask Hitch because she's the real expert in this area.

When it comes to the LITB, our internal rule is, make sure the damn thing looks good in Georgia font, and in KF7. That's the "rule." It ain't fancy, but mostly, it works.

I wish I had better, higher insight that I was willing to share, but that's about it. In my experience in dealing with Amazon, on the LITB, quite bluntly, they're guessing, too, typically.


Hitch

[slowsmile]

@jhowell...
"Cover Image does not meet the image quality bar of 300 PPI."

I could perhaps put in a plugin resolution check on all epub ebook images. At the moment, I'm not sure that Bundled Python's Pillow module would be able to get the image resolution. I'll have a look and will put in a resolution check if I can do it.

"Cover image occupies 100% of the screen, therefore the image either needs to be greater than 1200 PX width or 1800 PX height."

The above problem is covered by my plugin's dual formatting check. If a 'not dual formatted ' warning is given then you can resolve that by simply running the AddKindleMediaQueries plugin which automatically dual formats all ebook images for optimal display on both KF8 and KF7 devices.

If you're not bothered about dual formatting your ebook images and prefer just to format your smaller images(ie images less than max screen size) only for KF8 then you can do this buy formatting your smaller ebook images using inline styling and percentage values(which represent percentage of current screen width values). Simple example below:

<p class="image-style"><img alt="" src="../Images/image0.jpg" style="width: 20%;height: auto;"/></p>

But if you want your KF8 ebook images to be max page size across all KF8 device screens then you can also format them like this(and you shouldn't get errors):

<p class="image-style"><img alt="" class="kf8only" src="../Images/image0.jpg" style="width: 100%;height: auto;"/></p>

Generally speaking you should also bear in mind that Kindle always prefers the "shrink to fit" approach for adding ebook images at max screen size which means that they prefer using interpolation -- you add an image that is larger than max screen size and Kindle will happily use "shrink to fit" to fit it on the current screen. This is more accurate than expanding a smaller image to fit the page or screen(extrapolation) which can give problems like pixelation. Which is why Kindle usually gives warnings if extrapolation(or expand to fit) is used for max-page-size ebook images.

[slowsmile]

Update: The plugin has the following changes in v0.1.2:

* The plugin will now give a warning if there is a cover image file in the epub. There should be no cover image on upload to KDP as per the Kindle Guidelines. Thanks to st_albert and Hitch.

* The plugin user can now suppress any plugin warning by accessing the KDPValidator.json file and changing any of the listed warning values to "false". Initial default warning values are all set to "true". Thanks to DiapDealer.

[slowsmile]

@jhowell...Unfortunately the python Pillow module does not appear to be able to determine the resolution(pixels per inch) of an image, so I'm afraid there's no way that I can check ebook image resolution with this plugin.

[Doitsu]

Originally Posted by slowsmile

* The plugin will now give a warning if there is a cover image file in the epub. There should be no cover image on upload to KDP as per the Kindle Guidelines.

There's a typo in the plugin description and the cover page warning. KindleGen doesn't support Cover html pages, but it does of course support embedded cover images. You might want to change the wording of the message.

Originally Posted by slowsmile

@jhowell...Unfortunately the python Pillow module does not appear to be able to determine the resolution(pixels per inch) of an image, so I'm afraid there's no way that I can check ebook image resolution with this plugin.

Pillow supports dpi queries. Here's a snippet:

    imgdata = bk.readfile(cover_id)
    img = Image.open(BytesIO(imgdata)).convert('L')
    xdpi, ydpi = img.info['dpi']
    if (int(xdpi) or int(ydpi)) < 300:
        print('dpi is less than 300.')

[slowsmile]

@Doitsu...

"There's a typo in the plugin description and the cover page warning. KindleGen doesn't support Cover html pages, but it does of course support embedded cover images. You might want to change the wording of the message."

I'm not really sure what you mean by "support embedded cover images". The reason I advise removal of the cover.xhtml file from the epub was because both st_albert and Hitch advised me(further up on this thread) to add that warning. They should know because they are both professional formatters. The Amazon product image will automatically be added to the epub as the cover image file on KDP conversion. Remember also that this plugin only checks epub 2.0 files for upload to KDP. This plugin cannot check epubs formatted as KFX or epub 3.

Pillow supports dpi queries. Here's a snippet:

 imgdata = bk.readfile(cover_id)
    img = Image.open(BytesIO(imgdata)).convert('L')
    xdpi, ydpi = img.info['dpi']
    if (int(xdpi) or int(ydpi)) < 300:
        print('dpi is less than 300.')

My thanks for your advice and for the above code. I searched high and low in the python docs and couldn't find anything on Pillow handling image resolution. I'll get that implemented in my next plugin update.

[slowsmile]

@jbhowell...Concerning your cover image resolution check request. Unfortunately, I've just realised that I cannot implement the epub cover image resolution check because you should not have a cover image file in your epub when you upload to KDP(as advised by st_albert and Hitch further up on this thread). There is also a cover image warning in the plugin already i.e. a cover image file should not be in your epub when you upload to KDP.

[jhowell]

Originally Posted by slowsmile

@jbhowell...Concerning your cover image resolution check request. ...

You misunderstand me. I was not requesting a feature for this plugin. I was pointing out a new feature that appears to be coming to a future release of Amazon's Kindle Previewer. The sample messages included in my post were taken from that program.

I agree that it is best not to include a cover page/image in an e-book uploaded to KDP since that is supplied separately in the publishing process. Still, it appears that Previewer will be checking cover images.

The simplest explanation is that Amazon is assuming that you will include your cover in the book you are previewing, whether or not you include it in the file that you eventually upload to them.

A more far out possibility is that Amazon is planning to allow you to preview your finished book using the Kindle Previewer after it has been uploaded and processed by them, but before it is actually published. Evidence pointing to this possibility is that the latest Previewer now allows you to sign into your Amazon account and also contains apparently unused code to download books from their internal servers for previewing.

[DiapDealer]

Originally Posted by slowsmile

@jbhowell...Concerning your cover image resolution check request. Unfortunately, I've just realised that I cannot implement the epub cover image resolution check because you should not have a cover image file in your epub when you upload to KDP(as advised by st_albert and Hitch further up on this thread). There is also a cover image warning in the plugin already i.e. a cover image file should not be in your epub when you upload to KDP.

You're conflating things again.

KDP warns against including a cover PAGE (meaning an xhtml file used for the sole purpose of displaying a cover image).

KDP has no issue with including a properly prepared, manifested cover IMAGE that is identified through KDP's proscribed methods.

The request was that you change the warning that KDP doesn't allow cover IMAGES to KDP doesn't allow cover PAGES

Same for the request to check the image resolution of images. It is certainly possible (as Doitsu pointed out), and it's certainly allowed, since KDP does (and always has allowed cover IMAGES to be present in uploaded epubs)


Cover IMAGES: yes, great, allowed--encouraged actually by the Amazon Kindle Publishing Guidleines.

Cover PAGES: no, bad, KDP doesn't want.

You should be warning about the addition of cover PAGES and not cover IMAGES.

[slowsmile]

@DiapDealer...I've changed the cover image warning to a cover page warning in the release notes. But I now admit to being somewhat confused because you appear to be disagreeing with what both st_albert and Hitch have been saying on this thread about not having a cover.xhtml file in your epub when you upload to KDP.

Here is what Hitch has said about the cover.xhtml file in this thread:

"We make our files as does St. Albert--we build our ePUB, get a working, ePUB-checked copy, and then we remove the cover.xhtml page/file. We leave the meta pointing at the cover, as well as the Guide (for the Go To functionality).

Honestly, we haven't made a MOBI from an ePUB with a cover.xhtml file in at least 5 years, possibly longer. As long as Amazon has been inserting the covers "for" the publishers."

But you've said this in your last post:

"Same for the request to check the image resolution of images. It is certainly possible (as Doitsu pointed out), and it's certainly allowed, since KDP does (and always has allowed cover IMAGES to be present in uploaded epubs)".

Who is right about removing or not removing the cover.xhtml file? You or Hitch?

I really don't want to argue about whether the cover.xhtml file should be in the epub or not. I just want to know who is right since you and Hitch seem to have directly opposing opinions on whether the cover.xhtml file should be removed or not before upload to KDP. You also keep referring to the cover page and cover image while I've been talking about nothing but the cover image file -- cover.xhtml.

[DiapDealer]

Originally Posted by slowsmile

@DiapDealer...I now admit to being somewhat confused because you appear to be disagreeing with what both st_albert and Hitch have been saying about not having a cover.xhtml file in your epub when you upload to KDP on this thread.

I can assure that I am not disagreeing with them about anything (as I am sure they will confirm shortly). I'm not entirely certain, to be honest, why you're having such a difficult time understanding the distinction between a cover PAGE and a cover IMAGE.

I'll try again.

ANY *.xhtml file intended (and semantically marked) as a cover PAGE should not be included in an epub you upload to KDP.

But that has nothing to do with a cover IMAGE being present (and properly marked as such and resolution-compliant per the Kindle Publishing Guidelines) in the epub--which is allowed and encouraged.

[slowsmile]

@DiapDealer...Yes, I am still confused by what you say.

On the one hand you are saying that a cover PAGE(aka cover.xhtml??) should not be included in an epub that you uploaded to KDP. Then you say that a cover IMAGE is allowed.

But isn't the cover IMAGE situated in the cover PAGE ??

So how can you not have a cover PAGE while at the same time have a cover IMAGE in an epub??

Unless I'm missing something, you seem to be inferring that the cover IMAGE is not situated in the cover PAGE but is entirely separate from the cover PAGE. I admit that I am having a problem with that.

How can a cover IMAGE be present when the cover PAGE is not there??

[jhowell]

I am also confused by the cover issue. I do know that using cover HTML is a no-no.

I have been assuming that you can just leave out the cover image altogether and that Amazon would automatically insert the separately uploaded marketing cover as the internal cover. Hitch implied that is the case earlier in this thread.

Looking at the Amazon Kindle Publishing Guidelines (version 2018.2) section 4.2 is titled "Internal Content Cover Image Is Mandatory" and lists two methods of linking to a cover image from the OPF. It also states "Do not add an HTML cover page to the content in addition to the cover image." So, according to that document, the internal cover image is required.