Illustrations quality and resolution

[j.p.s]

Many people are unhappy with the resolution of illustrations in e-books, particularly maps. This gets mentioned in a number of threads. I think if reviews mention illustration quality and book readers base their buying decisions in part on illustration quality and let retailers and publishers know about it, that overall illustration quality will improve. It would be good have reference images to serve as examples. I will start this off will some suggestions below, fully expecting these to eventually be replaced by better examples suggested by others, at every quality level.

There are a number of ways to improve illustration quality in e-books. Mainly, they need to be larger, clearer, and better encoded. Line drawings and maps should be PNG instead of JPEG, yet most such drawings that I come across are JPEG. JPEG is bad for these types of images in 2 important ways. JPEG is designed for photographic images, and is excellent for this purpose. But JPEG line drawing have visible artifacts and require quite a bit more space than PNG or GIF. When e-books are created from older works, the illustrations are often scanned from a paper copy of the book. In some of those it is possible to detect the text on the other side of the page, and even the next page after. Another problem is that some platforms need better support for image zooming.

This version of 'War and Peace' is free at Amazon at the moment and has several maps that look decent on my Kindles, but are not very demanding in detail and I have not studied much yet.

http://www.amazon.com/gp/product/B00JCDK5ME
See also this thread:
https://www.mobileread.com/forums/sho...d.php?t=246114

The Amazon free sample of The Heroes by Abercrombie has a map, see this thread:
https://www.mobileread.com/forums/sho...=242848&page=2

'Seven Pillars of Wisdom' by T.E. Lawrence
http://gutenberg.net.au/ebooks01/0100111h.html
has 4 detailed maps and several line drawings. These are small even for 600x800 pixel displays and suffer from the text on other side of page and next page problems and JPEG artifacts. These images look "OK" on the web, unless you are trying to read the smaller text on the Maps. On 166 DPI and higher e-readers, the text is even harder to read.

There are 4 e-book versions of this book on Amazon, only 2 seem to be illustrated based on the free samples. One has a photograph of one of the maps. The other (free sample) has 3 of the maps. They seem to have been lifted from the Project Gutenberg of Australia site then contrast enhanced.

The free Kindle sample for 'Seven Pillars of Wisdom: A Beautifully ...' is at:
http://www.amazon.com/Seven-Pillars-...dp/B00CONFDTY/

I now think its map image is a color scan oddly split into 2 images, left and right. None of the line drawings are in the free sample portion.

The free Kindle sample for 'Seven Pillars of Wisdom [Illustrated with ...' is at:
http://www.amazon.com/Seven-Pillars-...dp/B004XMQ6J0/

Three of the maps and none of the line drawings are in the free sample. This is the edition that I think the images were lifted from the PG Aus site.

[j.p.s]

Placeholder for future organized post.

[GeoffR]

I am pretty much resigned to the fact that if I want readable maps, correct spelling, and other such features in my ebooks then I will probably have to do some of the work myself. Publishers just don't seem to care about those things as much as authors or readers do.

I just finished C. J. Cherryh's Fortress in the Eye of Time published by HarperCollins. The map included by the publisher was a very poor quality 294x377 scan, even zoomed to fill my ereader's screen it was pretty much unreadable.

But in this case the author has much higher quality scans avaliable on her blog site, so it was a simple matter to open up the epub and replace the publisher's useless map with a good one.

[j.p.s]

Originally Posted by GeoffR

I am pretty much resigned to the fact that if I want readable maps, correct spelling, and other such features in my ebooks then I will probably have to do some of the work myself. Publishers just don't seem to care about those things as much as authors or readers do.

I just finished C. J. Cherryh's Fortress in the Eye of Time published by HarperCollins. The map included by the publisher was a very poor quality 294x377 scan, even zoomed to fill my ereader's screen it was pretty much unreadable.

But in this case the author has much higher quality scans avaliable on her blog site, so it was a simple matter to open up the epub and replace the publisher's useless map with a good one.

Thanks for bringing this up. Reference images on the web are one of the possible mitigations for the problem. I forgot to mention it in my first post, but it does come up in the mobileread thread I referenced. Since Mr. Abercrombie would prefer to not even have maps in printed books, it is very nice that he makes them available on the web. I wish publishers would get on board with this.

http://www.joeabercrombie.com/maps-for-the-heroes/

I will have more to say about it this weekend.

[ATDrake]

Depending on how old the e-book file is, part of the quality issue (at least for Amazon-supplied titles) may be that up until fairly recently, the Mobi format had a strict limit for image filesize (eventually boosted from 64 to 128 kb as of KindleGen build 1.1 a couple of years ago) and would downgrade anything larger than that during the conversion.

Nowadays, the Kindle Publishing Guidelines say you can have up to 5 mb for an individual image (the section on GIFs still mentions a 127 kb limit, so I don't know if they didn't update this portion, or the 5 mb allowance is for JPEG/PNG only), but anything from before then was likely supplied to Amazon using the older tools which automatically made low-res versions regardless of what the publisher originally put in.

[j.p.s]

Originally Posted by ATDrake

Depending on how old the e-book file is, part of the quality issue (at least for Amazon-supplied titles) may be that up until fairly recently, the Mobi format had a strict limit for image filesize (eventually boosted from 64 to 128 kb as of KindleGen build 1.1 a couple of years ago) and would downgrade anything larger than that during the conversion.

Sure, but take for example the image: http://www.cherryh.com/WaveWithoutAS..._ivrel_map.png
at the blog http://www.cherryh.com/WaveWithoutAShore/?page_id=3273 mentioned by GeoffR above.

It is 2352 x 3162 and 100 kilobytes. I made a JPEG version that is 509 kilobytes and a 4bit (16 grays) PNG that is 72 kilobytes. That is a taller image than any current reader screen, yet the number of bytes almost meets the oldest file size restriction, while the JPEG is 5 times larger. So quite high quality line drawings can require few bytes as PNG.

Originally Posted by ATDrake

Nowadays, the Kindle Publishing Guidelines say you can have up to 5 mb for an individual image (the section on GIFs still mentions a 127 kb limit, so I don't know if they didn't update this portion, or the 5 mb allowance is for JPEG/PNG only), but anything from before then was likely supplied to Amazon using the older tools which automatically made low-res versions regardless of what the publisher originally put in.

Doesn't Amazon continue to restrict total file size for the lowest priced books because of data transfer costs and even deduct data transfer fees from royalties for higher priced books that have large file sizes? The five maps in 'The Heroes' take far more bytes than the entire rest of the book. Higher quality JPEG versions would need far less space.

[ATDrake]

Originally Posted by j.p.s

That is a taller image than any current reader screen, yet the number of bytes almost meets the oldest file size restriction, while the JPEG is 5 times larger. So quite high quality line drawings can require few bytes as PNG.

Unfortunately, the older Mobi format (not sure about AZW3) didn't support PNG, and IIRC, also auto-converted everything to GIF internally unless you told it otherwise, so that probably complicated matters.

But yeah, people often don't know when to use PNG versus JPEG.

Originally Posted by j.p.s

Doesn't Amazon continue to restrict total file size for the lowest priced books because of data transfer costs and even deduct data transfer fees from royalties for higher priced books that have large file sizes?

I don't know if they still do, but certainly at one point, people were using the KindleStrip utility in the Kindle Formats forum to cut down their filesize by removing the added sources in the files they got from using KindleGen.

Well, at least with public domain books, if one is sufficiently motivated, the original scan sources (or a reasonable alternative) can usually be found and cleaned up to upgrade disappointing files.

[JSWolf]

Originally Posted by j.p.s

Thanks for bringing this up. Reference images on the web are one of the possible mitigations for the problem. I forgot to mention it in my first post, but it does come up in the mobileread thread I referenced. Since Mr. Abercrombie would prefer to not even have maps in printed books, it is very nice that he makes them available on the web. I wish publishers would get on board with this.

http://www.joeabercrombie.com/maps-for-the-heroes/

I will have more to say about it this weekend.

I've already linked to that very same site in another thread that you linked to a few messages previous to the one I an quoting.

[j.p.s]

Here is the more detailed information for the Amazon free samples of 'Seven Pillars of Wisdom' that have line drawn maps as images. I think the images from the second one are good examples of some of the points I want to discuss in this thread.

The free Kindle sample for 'Seven Pillars of Wisdom: A Beautifully ...' is at:
http://www.amazon.com/Seven-Pillars-...dp/B00CONFDTY/

I now think its map image is a color scan oddly split into 2 images, left and right. None of the line drawings are in the free sample portion.

The free Kindle sample for 'Seven Pillars of Wisdom [Illustrated with ...' is at:
http://www.amazon.com/Seven-Pillars-...dp/B004XMQ6J0/

Three of the maps and none of the line drawings are in the free sample. This is the edition that I think the images were lifted from the PG Aus site.

[j.p.s]

The whole point of JPEG is compression. Its computational cost and lossiness are worthwhile because its compression ratio for photographic images can be enormous with only barely detectable quality degradation. But the characteristics of line drawings are different from photographs, so JPEGs of line drawings suffer in comparison to PNG, both in compression ratio and image quality. Even for photographs, JPEGs should not be used until the final image, because quality degradation accumulates with each step.

Gray scale images are usually represented as rows of 8 bit pixels with values of 255 being white, 0 black, and the rest the intermediate shades of gray. An image 600 pixels wide and 800 pixels high would require 480000 bytes, which is known as the uncompressed size. The heroes-1.jpg at the Joe Abercrombie site is 2048 by 1448 pixels, or 2965504 bytes uncompressed. The size of the JPEG image is 2764773 bytes, a mere 6.7% compression. I had thought that Joques was exaggerating for effect when he wrote: "No compression at all, it seems." in https://www.mobileread.com/forums/sho...=242848&page=2, but for JPEG 6.7% compression is pretty much no compression at all. A straight conversion from JPEG to PNG results in a file 1711169 bytes long, for a compression of 42.3% and 38.1% smaller than the JPEG. Without having to encode the JPEG artifacts, the PNG would be significantly smaller.

These are still 256 gray level images, but e-ink can only display 16 gray levels, which are also plenty for showing line drawings on LCDs. 4 bit (16 color) PNGs are even less storage space than 8 bit PNGs. This particular image also has a lot of scanning noise, which boosts the image size in bytes for both JPEG and PNG. This is easily seen by stretching the contrast of the bright parts of the image (by mapping bright gray / dull white to full black). This can be easilt done with Tools->Color Tools->Curves in GIMP and I assume Photoshop. One of the best ways I know to make JPEG artifacts glaringly obvious is to invoke Enhance->Equalize in the display application from ImageMagick. Saving a line drawing as a 4 bit PNG cleans up a good bit of the scanning noise in addition to shrinking the file size. A 16 level PNG of heroes-1 is 811205 bytes long, 72.6% compression.

According to Joques, the full epub book is 3.6MB and the 5 maps are 714x502 and 300KB each, or 41.6% of the book. I made 714x505 4bit PNG versions of the Maps from the large versions on the web site. They were all 125KB, a reduction of over 50%, reducing them to less than 20% of the book.

This is just one case and results can vary a lot in both directions, but for line drawing, PNG should almost always be a big win over JPEG. I wasn't able to extract images from the azw3 version of the free sample and the azw version was obviously modified by the kindle publishing process, but I was able to determine that it also came from a noisy scan. Cleanly scanned to a lossless file type and touched up will compress better than noisy scans straight to JPEG, even if the final file type is JPEG. Starting with a line drawing generated with a computer application will do much better still.