11-30-2012, 05:28 PM | #1 |
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Image problem
Hi. I'm an author and I format my own books.
I started out on Kindle, but I always did my formatting in epub format as it gives me far more options to make a decent layout. From epub I can convert to any desired format... So far so good… until I bought a Glo to look at my epubs on an actual device (until then I had only seen them in apps). Here's the problem: one of my covers (the one of "Gambit"), which renders fairly well on Kindle, looks patchy on the Glo. It's not a picture, but artwork and the best I can describe it is by saying that parts look like a topographical map. The colors and shades should blend into each other, but they don't. Is there anybody who knows what's the matter? Have you noticed something like this before? Is the image badly designed? Is there a difference between epub-devices in how they render images? Last edited by Andrew Ashling; 11-30-2012 at 06:37 PM. |
11-30-2012, 05:36 PM | #2 |
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Perhaps you should show us a picture of that patchy cover for a better understanding of the problem
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11-30-2012, 06:23 PM | #3 | |
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I know how to do that on the Kindle but, as I said, the Kindle renders it fairly well. But here is an epub with only the cover: |
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11-30-2012, 06:41 PM | #4 |
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While I'm asking…
I also noticed that there is a certain deterioration, more specifically a loss of sharpness, when you put an image in svg-tags. Does anybody know whether this is a Kobo-bug or an svg/epub bug? |
11-30-2012, 07:19 PM | #5 |
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The Kobo keeps cover images internally as GIF's. If you try to save your cover e.g. with Photoshop as GIF image, you'll see similar patches. Attached is a screenshot from the Photoshop dialog before saving. No idea how to avoid this - maybe it needs more dithering in the original cover.
And the grayscale rendering on the Kobo seems to increase the problem additionally. Last edited by Koboyashi; 11-30-2012 at 07:24 PM. |
11-30-2012, 07:43 PM | #6 | |
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I converted the jpg cover to gif - grayscale with the GIMP Although it has some problems they're not nearly as pronounced as on the Kobo. Could it be that the Kobo software uses a very low resolution? Anyway, thanks for the info. I'd love to hear from people who have other epub devices. Last edited by Andrew Ashling; 11-30-2012 at 07:46 PM. |
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11-30-2012, 09:23 PM | #7 |
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Firstly, I am doing this on a Kobo Touch, not a Glo, but the cover handling is identical.
Firstly, where are you looking at this? While reading the book, or in the library lists or the sleep cover? The sleep cover should be nearly the same as when reading the book. The Kobo devices generate cover images from the first page of the book when they are to be displayed. The images are JPEGs (not GIFs) with a different extension. For some reason Kobo uses "parsed" instead of JPG. With the firmware version you are running (probably 2.1.5 but it hasn't change for any firmware available for a Glo), there can be three cover images generated. These are in different sizes depending on the use. The last part of the generated filename gives the use and size. "N3_LIBRARY_GRID" is used in the library lists, "N3_FULL" is used for the home screen and the sleep cover and "N3_LIBRARY_FULL" is used for the details screen. When reading the book, the cover page is sized a little differently than the sleep cover because of the page number area at the bottom of the screen. The sleep cover is rendered for the full sceen, but when reading, the page is rendered within the viewable area. Looking at the cover on my Touch and in Windows with my image viewer, I can see what you mean. The Touch shows the problems you are talking about, but I didn't think they were to bad. I have covers that look a lot worse. Resizing and converting to greyscale on the PC does a much better job. When I put the resized image on my Touch, it showed the problems the same as letting the device do it. The screen is 600*800 and 16-level grey scale, so that should mean it would be display the same. That suggests the driver or software on the device isn't rendering the images as well as it could. Last thing, you are using the following for the cover: Code:
<svg xmlns="http://www.w3.org/2000/svg" height="100%" preserveAspectRatio="xMidYMid" version="1.1" viewBox="0 0 800 1200" xmlns:xlink="http://www.w3.org/1999/xlink"> <image height="1200" width="800" xlink:href="../Images/cover.jpg"></image> </svg> Code:
<svg xmlns="http://www.w3.org/2000/svg" height="100%" width="100%" preserveAspectRatio="xMidYMid meet" version="1.1" viewBox="0 0 800 1200" xmlns:xlink="http://www.w3.org/1999/xlink"> <image height="1200" width="800" xlink:href="../Images/cover.jpg"></image> </svg> Good luck with the book. |
12-01-2012, 11:25 AM | #8 |
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Oops, there I was completely on the wrong track - they are JPEGs of course.
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12-01-2012, 01:54 PM | #9 |
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Thank you all for your responses.
@davidfor Thanks for taking the time to provide such an extensive explanation. I learned a lot. For a good understanding: I'm based in Belgium and bought my Glo at Fnac in Antwerp (a so-called FNAC-Book). It had a modified version of the firmware (version 1.9 or something). My computer OS is Linux, as is the OS of the Kobo. I "liberated" the Glo thanks to some instructions here on MR. This was a very fast, painless operation, completed without a hitch. Current version is 2.1.5 (r43939). I installed a few fonts of my own. Re: Different cover images. I noticed that the cover renders as good as can be expected in sleep modus. The library view is so small it hardly matters, but even so it seems to be all right. The problem is only with the cover view in reading modus. On one hand I'm happy because there seems to be nothing wrong with my cover image. The problem is with the Kobo, and more specifically when it adds margins to the picture. This is confirmed by another experience I had. My book(s) contain full-page maps. When I just use the image-tag and add a "{text-align: center;}" class to the page, they appear smaller but sharper. When wrapped in svg-tags, sharpness is lost and they appear ragged, but bigger. There are three possibilities, as far as I can see:
For the cover it doesn't help to omit svg-tags (let alone you then lose scalability which you need for display on other devices like tablets, iPads and mobile phones) because the Kobo forces the margins on the cover page. Question: Is there a css code that could overrule the Kobo's page settings? I have a few other remarks and questions which I will post separately at a later time. Sorry to go on about this, but I like to offer my readers value for money, and I want my books to display as good as I can make them on as many devices as possible. In this file I added the same map twice, once without and once with svg-tags (I adopted davidfor's version): Last edited by Andrew Ashling; 12-01-2012 at 07:59 PM. |
12-01-2012, 08:55 PM | #10 |
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I upgraded the firmware to version 2.2.1 (r44772).
Same issues. |
12-02-2012, 07:55 AM | #11 | |||||
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With the Glo's higher resolution screen, I would expect the svg version to be resized to fit the screen taking into account the margins and bottom section. Going from 600*800 of the image to 1024*758 for the screen, would cause some distortion, but I'm surprised it is as bad as you are seeing. I assume the the img version to be displayed without being resized. That should mean it would look OK. Quote:
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12-02-2012, 02:56 PM | #12 | |||
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It seems the devices have ways to overrule (some) settings of the file. Since, on the Kobo, svg/img tags make a difference for the maps but not for the cover, I'm guessing the firmware itself wraps the image on the designated cover-page in svg-tags, but doesn't do this for illustrations in the rest of the book. Quote:
For now I'm thinking of going with svg-wrapping only for the cover. It makes no difference for the Kindle. For the Touch they are acceptable according to you, and for the Glo the illustrations look better in simple img-tags. Quote:
Code:
<style type="text/css"> @page {padding: 0pt; margin:0pt} body { text-align: center; padding:0pt; margin: 0pt; } </style> I noticed in the font-settings there is an item "Document Default." It doesn't seem to do much. IMHO that should be a separate setting and not one under "Fonts." E.g. I use a special font for titles, but not for the main text as I want the reader to have a choice. As it is, the Kobo always honors the document defaults (which makes that specific setting rather superfluous). On a side note: on the Glo, the preloaded font "Avenir" renders text bold where it should render it in italic. Probably a simple mistake in the naming convention, but nobody seems to take the trouble to repair it. I'm planning to buy a Sony Reader Touch PRS-T2 and see how the book behaves on that device. I'll report my findings. Last edited by Andrew Ashling; 12-04-2012 at 08:41 AM. |
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12-04-2012, 06:05 AM | #13 | ||||||
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12-10-2012, 06:43 PM | #14 |
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I bought a Sony Reader Touch PRS-T2 last week and had some time to play around with it.
As it turns out, most (if not all) of the problems are Kobo-specific. The Sony renders the images perfectly, or as well as can be expected, and at a lower resolution too. I also noticed that some titles, when they run over two lines, look cramped on the Kobo, but perfectly normal on the Sony. There are some problems with margins, especially bottom ones. I think I'm going to use the Sony to test my files on, and then see whether the result is acceptable on the Kobo (and the Kindle). The Kobo is a fine device, and the lit screen is beautiful. I also love the user configurability, but otherwise the OS is a bit of a work in progress. I'm sure things will get better with each upgrade. |
12-10-2012, 10:16 PM | #15 |
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E-ink screens only have 16 shades of grey. That's why you see the banding instead of smooth gradients. Most readers now do an exclent job of dithering images so they look smooth, (like the old ink jet printers.). Sony has done that for a long time (at least, since the prs-650). Kindle only started doing that after one of the patches on the Touch. (the original touch firmware looked just like the Kobo.). Kobo hasn't really improved the rendering of image shading yet, however.
Edit: actually, most all printers, old and new alike, use dithering. I don't know why I thought of that comparison. |
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