04-23-2016, 06:45 AM | #1 |
Connoisseur
Posts: 87
Karma: 39898
Join Date: Jul 2013
Location: Canberra, Australia
Device: Kobo Clara HD, Kobo Libra H2O
|
Images ok on PC, too small on reader
I recently purchased an ebook "e - the story of a number". It contains numerous equations set within the text, most of which are png images. These equations display at an appropriate size when I view the book in Adobe Digital Editions or with the Calibre ebook viewer on the PC, but on my Aura HD the equations are (relative to the surrounding text) considerably smaller. This makes them quite difficult to read, especially when they involve things such as fractional exponents. Is there anything I can do to increase their relative size on the Aura HD. There is also the secondary problem that the equations are centred (as they should be) when viewed in either ADE or Calibre, but appear left-justified on the Aura HD.
I've attached a couple of screenshots - ade.png from the ADE reader on the PC, and aura.png from the ereader - showing the same section of text. The ereader is running current firmware. |
04-23-2016, 08:53 AM | #2 |
Wizard
Posts: 3,821
Karma: 19162882
Join Date: Nov 2012
Location: Te Riu-a-Māui
Device: Kobo Glo
|
As to the equation size: does the size of the equation change when you change the font size? If not then it is most likely a common publishing mistake where the equations are set at a fixed (pixel) size, and so will always look too small on high-dpi screens or when a larger font size is selected..
If that is the problem then the only solution is to edit the book to fix the mistakes. There are two approaches: one is to use image tools such as imagemagick to increase the size of the bitmap images to suit the device and selected font size; another (better but more time-consuming) approach is to edit the stylesheet and set the height and width of each image so that they resize automatically in proportion to the font size. Edit: If you have the ImageMagick tools, then resizing the images might (depending on how the publisher has set the image sizes in the stylesheet) be as simple as using Calibre to unpack the ePub, running the following command in the directory containing the images, and then rebuilding the ePub: Code:
mogrify -resize 150% *.png As to the alignment. Do the equations become centred again when you set the justification button (Aa menu) to "Off"? (I guess this is a KePub book?) Last edited by GeoffR; 04-23-2016 at 10:12 AM. Reason: added more detail about the two approaches to fixing the size problem |
Advert | |
|
04-26-2016, 03:58 AM | #3 |
Connoisseur
Posts: 87
Karma: 39898
Join Date: Jul 2013
Location: Canberra, Australia
Device: Kobo Clara HD, Kobo Libra H2O
|
No, the size of the equations does not change when the font size is changed.
Yes, setting justification to off gets the equations centred on the reader screen (it is a kepub). I had a fiddle with the style used for the images to see what improvement I could get for their display on the reader. It doesn't work too well, as even just the single line equations vary considerably in their native height and width, and setting a specific value in the style for the width or height (as opposed to auto) gives quite a different scale depending on what is in the image. For example, both the attached images are single line equations, but have different heights and scale quite differently unless height and width are left at auto. I'll have to try your other suggestion, of using Imagemagick to enlarge all the images by the same amount. Edit: I used Sigil and Imagemagick to enlarge all the png images to 150%. That makes them much easier to read on the Aura HD. Last edited by Nick Payne; 04-26-2016 at 08:13 AM. |
04-26-2016, 07:02 AM | #4 | |||
Wizard
Posts: 3,821
Karma: 19162882
Join Date: Nov 2012
Location: Te Riu-a-Māui
Device: Kobo Glo
|
Quote:
The ePub reader works differently and only overrides <body> (but not subclasses of body) and so often works better, but it depends on the publisher not overriding the default alignment of the main text. There are firmware patches that can change the way the alignment is set in KePubs, to make it more like the ePub reader, but it is not really possible to get something that works well for all books without also editing the books to regularise their stylesheets, as there are so many different ways the publisher can structure the stylesheet. Quote:
(Edit: Another way would be to create an SVG wrapper for each image, as SVG gives a lot more options for dealing with image sizes than is possible just by styling the img class in CSS, but I think that would take at least as much effort.) The size of diagrams like the graph in your screenshot are probably better set as a percentage of the screen size (%) rather than proportional to font size (em). Quote:
Whichever method you use though, the results will depend a bit on the quality of the original images. If they are poor quality to start with then making them larger might not make them that much more readable. Last edited by GeoffR; 04-26-2016 at 07:20 AM. Reason: Another way would be to create an SVG wrapper ... |
|||
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Aura H2O ePub Images Small | elstoc | Kobo Developer's Corner | 13 | 09-19-2015 11:02 AM |
Icons or small images | techauthorbob | Sigil | 1 | 06-11-2012 11:52 AM |
small preview page images | goodnerd | Kindle Formats | 5 | 09-22-2011 11:39 AM |
My images are disappearing on small screen devices | sbrwake | Kindle Formats | 2 | 01-10-2009 09:01 PM |
Small Images on Vade Mecum with Sunrise | kg4dkf | Reading and Management | 1 | 07-21-2005 01:25 PM |