Editing epub in Calibre

milest · 09-16-2021, 10:48 AM

Have problems viewing maps (but not photos) in several epub books on my Kobo - as maps (as a page within a book) almost always display far too small to be legible, though if I read the ebook on my PC via Calibre, they display full size. Photos, though, usually display full size on the Kobo.

I know nothing about editing epub HTML though I have read internet tips about being able to do so via Calibre.

Trouble is, I have no idea as to what HTML properties on what items I could edit to increase map viewing size on my ereader.

Any ideas - or is this the wrong approach? I don't think it is a Kobo problem but rather that the book publisher has not done a good job on preparing the book for an ereader? Thanks.

Sirtel · 09-16-2021, 12:21 PM

It's a Kobo problem. You cannot zoom images in epubs on a Kobo.

The solution is to use the kepub format. KoboTouch Extended Driver will convert your epubs into kepubs while sending books to devices, but leaves the library copies as epubs only.

davidfor · 09-16-2021, 12:30 PM

As you are using a Kobo device, sending the books to the device a kepub might be better for books with maps and pictures. With kepubs, you can double tap on the image to open it in a view that supports zooming.

To do that, you can either use the KoboTouchExtended driver which will transform the books to kepubs when you send them to the device. Or the Kepub Output plugin to do a conversion. The latter is better if you do not want to send all books as kepubs.

If I do edit the book, I either wrap the image in an SVG so that it resizes to the screen. Or put a class on the img tag that sets either the width or height to 100%. Which I do depends on the aspect ratio of the image and which works best to maximise the image size.

theducks · 09-16-2021, 12:38 PM

Ooooo!
Stand by for many different opinions

Me, myself and I rotate maps to match the aspect of the device (typically Portrait) rather than the PC (landscape).
so they can fill the screen space.
I also use 0 margins (inherited to the image)

The other thing I do is make sure the width and height styles ARE NOT absolutes . That locks the sizes. Use % and auto (some devices may not honor this) values, this means it will adjust to fit. In addition, using max-width or max-height in absolutes Limits the size to keep the distortion within limits.

(I keep my editor preview window the same size as my device)
In the CSS find the class assigned to the image, try:

width: 100% /* was 1080px */ ;
height: auto /* was 1920px */ ;
(I commented out the old values just in case. YMMV)

DNSB · 09-16-2021, 01:08 PM

Quote:

Originally Posted by theducks

Ooooo!
Stand by for many different opinions

Just to toss my opinion into the ring. I prefer to use an SVG wrapper to display full page images. I also will rotate maps, etc. to portrait layout to allow them to better fit the screen.

As to what I mean by an SVG wrapper?

Code:

<style type="text/css">
@page {padding: 0pt; margin:0pt}
body { text-align: center; padding:0pt; margin: 0pt; }
</style>
</head>

<body>
  <div>
    <svg xmlns="http://www.w3.org/2000/svg" height="100%" preserveAspectRatio="xMidYMid meet" version="1.1" viewBox="0 0 2550 3300" width="100%" xmlns:xlink="http://www.w3.org/1999/xlink"><image height="3300" width="2550" xlink:href="../Images/map7.jpeg"/></svg>
  </div>

Where the 2550x3300 are the dimensions of the image (WxH). On a Kobo reader using kepub format, you can tap on the map to zoom which is handy.

gtriever · 09-17-2021, 09:25 AM

Since I know less than zero about coding, I open the book in Editor and then open each .jpg file individually. I then rotate the image until the longest side is vertical and resize that dimension to 1800px (keeping the Preserve Aspect Ratio). Clumsy, but effective in my case.

milest · 09-17-2021, 01:49 PM

I shall work my way through them, starting with the simplest ones (probably kepub if Calibre supports it).

But I am really impressed with all your helpfulness and explanations and look forward to being able to see maps in future and to learning more about the different options!

09-16-2021, 10:48 AM	#1
milest Junior Member Posts: 4 Karma: 10 Join Date: Nov 2011 Device: Kobo Glo	Editing epub in Calibre Have problems viewing maps (but not photos) in several epub books on my Kobo - as maps (as a page within a book) almost always display far too small to be legible, though if I read the ebook on my PC via Calibre, they display full size. Photos, though, usually display full size on the Kobo. I know nothing about editing epub HTML though I have read internet tips about being able to do so via Calibre. Trouble is, I have no idea as to what HTML properties on what items I could edit to increase map viewing size on my ereader. Any ideas - or is this the wrong approach? I don't think it is a Kobo problem but rather that the book publisher has not done a good job on preparing the book for an ereader? Thanks.

09-17-2021, 01:49 PM	#7
milest Junior Member Posts: 4 Karma: 10 Join Date: Nov 2011 Device: Kobo Glo	Thank you for all your tips I shall work my way through them, starting with the simplest ones (probably kepub if Calibre supports it). But I am really impressed with all your helpfulness and explanations and look forward to being able to see maps in future and to learning more about the different options!

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09-16-2021, 12:21 PM	#2
Sirtel Grand Sorcerer Posts: 13,455 Karma: 239219453 Join Date: Jan 2014 Location: Estonia Device: Kobo Sage & Libra 2	It's a Kobo problem. You cannot zoom images in epubs on a Kobo. The solution is to use the kepub format. KoboTouch Extended Driver will convert your epubs into kepubs while sending books to devices, but leaves the library copies as epubs only.

09-16-2021, 12:30 PM	#3
davidfor Grand Sorcerer Posts: 24,905 Karma: 47303824 Join Date: Jul 2011 Location: Sydney, Australia Device: Kobo:Touch,Glo, AuraH2O, GloHD,AuraONE, ClaraHD, Libra H2O; tolinoepos	As you are using a Kobo device, sending the books to the device a kepub might be better for books with maps and pictures. With kepubs, you can double tap on the image to open it in a view that supports zooming. To do that, you can either use the KoboTouchExtended driver which will transform the books to kepubs when you send them to the device. Or the Kepub Output plugin to do a conversion. The latter is better if you do not want to send all books as kepubs. If I do edit the book, I either wrap the image in an SVG so that it resizes to the screen. Or put a class on the img tag that sets either the width or height to 100%. Which I do depends on the aspect ratio of the image and which works best to maximise the image size.

09-16-2021, 12:38 PM	#4
theducks Well trained by Cats Posts: 31,046 Karma: 60358908 Join Date: Aug 2009 Location: The Central Coast of California Device: Kobo Libra2,Kobo Aura2v1, K4NT(Fixed: New Bat.), Galaxy Tab A	Ooooo! Stand by for many different opinions Me, myself and I rotate maps to match the aspect of the device (typically Portrait) rather than the PC (landscape). so they can fill the screen space. I also use 0 margins (inherited to the image) The other thing I do is make sure the width and height styles ARE NOT absolutes . That locks the sizes. Use % and auto (some devices may not honor this) values, this means it will adjust to fit. In addition, using max-width or max-height in absolutes Limits the size to keep the distortion within limits. (I keep my editor preview window the same size as my device) In the CSS find the class assigned to the image, try: width: 100% /* was 1080px / ; height: auto / was 1920px */ ; (I commented out the old values just in case. YMMV)

09-17-2021, 09:25 AM	#6
gtriever Addict Posts: 285 Karma: 2125576 Join Date: Sep 2010 Device: Kobo Forma	Since I know less than zero about coding, I open the book in Editor and then open each .jpg file individually. I then rotate the image until the longest side is vertical and resize that dimension to 1800px (keeping the Preserve Aspect Ratio). Clumsy, but effective in my case.

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