Aura HD Images: possible to double the size?

[CmplxAdSys]

Originally Posted by GeoffR

Here is a recent thread on the issue: https://www.mobileread.com/forums/sho...d.php?t=265355

It all depends on how the publisher has done the css and html, in some cases you might find it easier to just resize the images themselves with tools such as ImageMagick, in other cases you can just edit the css, but in some cases there might be no option but to go through and edit each individual html tag.

If you could post an example of how a typical image is referenced from the html, along with the relevant css styles, then someone might be able to suggest the easiest way to do it.

Edit: AFAIK there is no way to do SVG just from CSS alone, you need to have a SVG wrapper for each individual image if there isn't one already.

Sure. Thanks! I'll also check out the newer thread.

The HTML is not entirely straightforward, so I'll give a snippet of the HTML, then show how it displays.

<p class="noindent">The third axiom states that the belief assigned to any set of events is the sum of the beliefs assigned to its nonintersecting components. Because any event <i>A</i> can be written as the union of the joint events (<i>A</i> <img alt="image" src="images/And.jpg"/> <i>B</i>) and (<i>A</i> <img alt="image" src="images/And.jpg"/> <img alt="Image" src="images/arrow.jpg" style="vertical-align:2px;"/><i>B</i>), their associated probabilities are given by<a href="#fn1" id="fn1a"><sup>1</sup></a></p>
<p class="eqimage"><a id="eq0104"/><img alt="Image" src="images/eq01_04.jpg"/></p>
<p class="noindent">where <i>P</i>(<i>A</i>, <i>B</i>) is short for <i>P</i>(<i>A</i> <img alt="image" src="images/And.jpg"/> <i>B</i>).

The image for how that displays (in Calibre and in the Kobo desktop app - on the H20, it's super-tiny) is attached.

Images have different classes in the CSS file. Equations that are centered are in the class "eqimage."

However, there are also some math symbols that are inserted inline with no class as you can see in the snippet above. I can manipulate them a little using nested CSS referencing (I tried .noindent img and .indent img and it seemed to work okay on my computer, but not on the H20). And then there are figure classes as well that display okay, so I probably won't be touching them.

The CSS sheet has the following style for "eqclass":

.eqimage {margin-top:1em; margin-bottom: 1em; text-align: left; text-indent: 1.25em;}

As I said, I tried adding adding height and width here using both em and %, but it didn't actually resize the image.

[CmplxAdSys]

Originally Posted by rashkae

If the book is a kepub, (either auto synced from Kobo, or sideloaded with Calibre and the Extended Kobo Driver plugin.), then you can double tap on images to open them in an "Image viewer" That will scale them up to the size of the screen, and allow you to zoom and pan as well.

Cool! That works well for my centered equations that I have trouble reading an is a good stopgap, although it's slightly awkward to zoom in to in-line math symbols that are displayed as images, yet surrounded by normal text. Thanks for the tip.

[GeoffR]

Originally Posted by CmplxAdSys

However, there are also some math symbols that are inserted inline with no class as you can see in the snippet above. I can manipulate them a little using nested CSS referencing (I tried .noindent img and .indent img and it seemed to work okay on my computer, but not on the H20).

What you have done should have worked, unless there is something else in the stylesheet that overrides it or perhaps sets max-height somewhere. I tested his and it appears to work in both ePubs and KePubs:

p.noindent img {height:1em;width:auto;}
p.eqimage img {height:auto;width:80%;}

However if the eqimage images are all different sizes then it might not look good, you would need to either go through and set a specific height to suit each individual image, or use ImageMagick to resize the jpg files instead.

Edit: Since the eqimages are actually text, they should really be proportional to the font size, so ideally you would set the height for a one-line equation to height:1em;width:auto; and set the height of multi-line equations to a multiple of 1em; then set an appropriate font-size in the parent paragraph (say font-size:1.5em; ) In this case you might also need to set the max-height and max-width to make sure the image still fits on the screen at large font sizes.

Edit2: You might not think this worth the time, but you could replace the inline images of individual symbols with actual glyphs from a font, which would look much better (it is what the publisher should have done in th first place.) Just embed a font SymFont that has all the symbols you need with @font-face, create a class like .syms {font-family:SymFont;} and then replace each <img alt="image" src="images/And.jpg"/> with <span class="syms">∧</span> etc. I do this for fiction books where the publisher has used a (usually extremely low resolution) bitmap of a letter instead of embedding a font that includes that letter. The display equations would take a lot more work though.

Edit3: Thinking a bit more about fixing up the image size used for bitmaps of equations without using SVG: The ideal is that the euation should change size proportional to the selected font size, but should not become so big that it no longer fits on the screen. The solution is to set the width proportional to the font size, but also set the max-width proportional to screen size.

For example, if the size of the bitmap was 100 pixels high and 800 pixels wide, (assuming a one-line euation) then something like this would do the job:

p.eqimage img {height:auto; width:8em; max-width:80%;}

[DNSB]

Originally Posted by CmplxAdSys

Alternatively, has anyone come up with any ideas on how to fix this problem besides those mentioned above?

Thanks in advance!

What I recently did rather than spend the time to try to make ~200 images in a textbook look good on an H2O, was to use 7Zip to open the ebook, extract the image files in a directory with a subdirectory called holder and then use ImageWorsener with a batch file to resize all the images I wanted to resize by 180% and convert them to greyscale. I then used 7Zip to insert the modified images into the ebook. The 180% came from 1080/600 BTW,. Not the greatest and some of the images definitely needed higher res versons but it was quick and dirty.

The command line looked something like this:

for %f in (*.jpg) do "imagew.exe -w x1.8 -grayscale -depthgray 4 -cc 16 -gsf s -dither none %f.jpg ./holder/%f.jpg"
pause

[CmplxAdSys]

Thanks, JeffR. I played around a little more and got it to work (I mistook the .eqimage class for images themselves. Modifying it in the way you listed, using p.equimage img worked). However, I found out that the publisher's formatting is really inconsistent; some images for equations are just given the class ".image" and some are given IDs using the a tag, so I also had to create instances for these as well in the CSS sheet. I'm sure there are more idiosyncrasies I missed, but I have the basics down.

Perhaps I will try DNSB's (thanks, too, DNSB!) and your suggestion if I have more time to either resize the images or replace the inline images with fonts.

[thatworkshop]

Does anyone who have opened their Aura HD know what's part number for the eInk screen? (for instance it's ED060XG1 for Kobo Glo).

[Linton]

I have reported mathematical equations being too small to read on Kobo e-readers to Kobo Support. They tell me its not a bug!!! As its not a bug its odd that equations are displayed properly on both the PC Kobo tool and the IPAD Kobo App withut any need to change the source.

[davidfor]

Originally Posted by Linton

I have reported mathematical equations being too small to read on Kobo e-readers to Kobo Support. They tell me its not a bug!!! As its not a bug its odd that equations are displayed properly on both the PC Kobo tool and the IPAD Kobo App withut any need to change the source.

The equations do not show correctly for kepubs on the Aura HD? Or are you using epubs there? Both the Kobo desktop application and the iOS app will be reading kepubs. Strictly, you cannot directly compare how epubs and kepubs are handled.

[GeoffR]

One thing to note when comparing a book on a high-pixel-density device with the same book on a PC, is that the PC viewing window is likely to be lower resolution. E.g. when I open a book in Calibre the viewer window is 800x600.

The fundemental problem with the way many publishers display images in their ebooks is that they are sized for a low-resolution device, usually 800x600. They might look fine in Calibre, or in the Kobo app on a PC, or on an old Kobo Touch, but the images will be too small for a high-dpi device like a H2O or GloHD.

There are ways to make the images resize automatically, but it is never going to look good on a H2O or GloHD if the resolution of the underlying bitmap was created to suit an 800x600 device. The only real solution is for publishers to either use much much higher resolution bitmaps, or to create proper scalable vector graphics images (or simply to embed fonts if the images are of text). There is just nothing the device or firmware can do to make the images both look clear and display at the right size if the publisher has only provided low-resolution bitmaps.

[dvd8n]

I updated my Aura HD to 3.18.0 today and the help that popped up, in the 'Reading Menu', had an entry 'Zoom in and out of Images'. I'd not noticed that before.

Great I thought I can read that book with the tiny illustrations without squinting.

But no - I can't get the menu option to appear. Anyone have any ideas why not?

[davidfor]

Originally Posted by dvd8n

I updated my Aura HD to 3.18.0 today and the help that popped up, in the 'Reading Menu', had an entry 'Zoom in and out of Images'. I'd not noticed that before.

Great I thought I can read that book with the tiny illustrations without squinting.

But no - I can't get the menu option to appear. Anyone have any ideas why not?

The image zoom is only in kepubs. If you want to use this, you will need to convert the books to kepub.

[dvd8n]

Ah. Oh well back to squinting I suppose.

Thanks.

[Linton]

Originally Posted by davidfor

The equations do not show correctly for kepubs on the Aura HD? Or are you using epubs there? Both the Kobo desktop application and the iOS app will be reading kepubs. Strictly, you cannot directly compare how epubs and kepubs are handled.

The books whether on the Ipad, PC or Aura HD are simply downloaded from the Kobo shop. So I assume they are kepubs - if not where do I get them from?

Like another contributor in this thread I see no sign of any Zoom in and out of images option - though this shouldnt be necessary.

[davidfor]

Originally Posted by Linton

The books whether on the Ipad, PC or Aura HD are simply downloaded from the Kobo shop. So I assume they are kepubs - if not where do I get them from?

As you can sideload books, and it isn't hard to convert from other formats to formats that Kobo ereaders support, you can get books from just about anywhere else. And, if you are buying from Kobo, most books in the shop have an epub version you can download.

Like another contributor in this thread I see no sign of any Zoom in and out of images option

You only see the zoom option on the bottom menu if the only thing on the screen is the image. Double tapping an image in a kepub will trigger the image viewer.

- though this shouldnt be necessary.

No, it shouldn't be necessary. But, for it to work properly, the person who put the book together has to know what they were doing. Most of them don't seem to. And unfortunately, each reader app or device interprets the standards differently or have different bugs. The book creators tend to concentrate on one or two of these and get it right there and then it doesn't work properly elsewhere.

But, if you have a book downloaded directly from the Kobo shop that looks different the ereader to the desktop application or other Kobo app, there might be a bug. Or, it might be differences in implementation because of the different hardware. To know, we need to look at the book. Can you point to the book? Maybe we can look at the sample and see what is going on.

[Linton]

Originally Posted by davidfor

.....
But, if you have a book downloaded directly from the Kobo shop that looks different the ereader to the desktop application or other Kobo app, there might be a bug. Or, it might be differences in implementation because of the different hardware. To know, we need to look at the book. Can you point to the book? Maybe we can look at the sample and see what is going on.

Thanks for your interest David. I have investigated further and it seems that with my books (kepubs) and e-reader (Aura HD) pictures are displayed at 2/3 the linear size of picrures on the IPAD Kobo App compared with the page size.

For example look at a preview of "The Irrationals" by Julian Havil, a few pages in from the start of Chapter 1 (page 12 of 86 with my font size) there is a timeline diagram (Figure 1.1). On an IPAD this diagram occupies the full width of the displayed page. On the Aura it takes up about 2/3 of the page width. So its 2/3X2/3 =4/9 the size, which makes it total unreadable.

Another example - "Infinite series" by James Hyslop. Around page 3 or 4 of chapter 1 there is the formula for a function (its a picture). The IPAD version is much larger on the page (its actually too large to fit) whereas the Aura version is less than half a page wide.

Hope that helps.