AZW3 to EPUB conversion: images cropped

[dr_Fell]

Hello, I have tried to solve this for few hours and I am stuck.

I am trying to convert my book from amazon (Java: The Complete Reference) to epub so I can read it on my Cybook Odyssey. After conversion it seems that the images are cropped (at least from left/right) by few pixels. Since code examples are in image (jpg) form it makes the book unusable, because important elements, like semicolons, parentheses etc. are often located near the borders.

I tried to limit max width with

div span img
{
 max-width: 90% !important;
}

or

div span img
{
 max-width: 530px;
}

Effect was visible, the image was smaller, but the problem remains (few pixels cropped on the sides). Problem is visible only on my Cybook Odyssey, Calibre Viewer displays those images without problem.

I think that I can eventually use some workaround by processing those images and adding few more pixels on each border - but I don't know how to access them.


Solution:
I downloaded images using book editor, edited them, then put it back to the book. It didn't work well with epub (don't know why - maybe I did something wrong), but it works with original AZW3 file.

I added 5px white border to images using ImageMagick tools (workaround so my reader just cuts those white border and not the actual image). Additionally I adjusted size and sharpened all images, so my reader won't have to change resolution on the fly (for quality and readability). I also set a bit of negative left margins during conversion, so that the images could be a bit wider.
The code is now much more readable than in the original files provided by Amazon .

If this can be helpful for anyone, here are command line examples on how to batch change size and sharpeness:

 magick mogrify -format bmp *.jpeg    //convert every jpeg image to bmp for further loseless processing

magick mogrify -filter Mitchell -resize 550x730^> -format bmp *.bmp  //downscale images that are wider than 550px or higher than 730px, leaving smaller images untouched

magick mogrify -bordercolor white -border 5x3 -unsharp 0x1.1+2+0 -format jpeg *.bmp     //add white border and sharpeness to every bmp image and save back as jpeg

and the margins:

div span img {
 margin-left:-15px;
}

[kovidgoyal]

calibre does not crop images during conversion, this is a bug in the reader you are using. And if you want to access the images, simply edit the azw3 using the calibre editor or use the unpack book tool.

[dr_Fell]

I managed to download images from book, add small white border to every one of them, then I deleted original images in Calibre editor and uploaded modified images with same names. Unfortunately new images are not visible... What am I doing wrong?

[JSWolf]

What you need to do to stop the images from being modified is to change the output profile to TABLET. By setting the output profile to tablet, Calibre will not resize the images at all.

[dr_Fell]

Originally Posted by JSWolf

What you need to do to stop the images from being modified is to change the output profile to TABLET. By setting the output profile to tablet, Calibre will not resize the images at all.

Hmm, I'd say this is not a problem with images resized by calibre, but rather badly rendered by my device. I tried what You suggested and nothing has changed (images cropped on the right and left and sometimes damaged at bottom).

If only I could replace images from epub with my modified versions, that would probably fix the problem. Any idea why this doesn't work? New images being a bit bigger than old versions (14 points wider and 6 points higher) could be the cause?

[davidfor]

Originally Posted by dr_Fell

Hmm, I'd say this is not a problem with images resized by calibre, but rather badly rendered by my device. I tried what You suggested and nothing has changed (images cropped on the right and left and sometimes damaged at bottom).

It would be a good idea to post the code as well as the styles for us to look at or try. Or use the Scramble plugin to generate a version of the book you can post.

If only I could replace images from epub with my modified versions, that would probably fix the problem. Any idea why this doesn't work? New images being a bit bigger than old versions (14 points wider and 6 points higher) could be the cause?

Try using "Unpack book". That will unzip the book into a folder. You can then replace the images and calibre can repack it.

[dr_Fell]

Thank You all for help! Problem seem to be solved. I have paid a lot of money (at least for me) for that book and I am glad I can use it now

I downloaded graphics, edited them, then put it back to the book. It didn't work well with epub (don't know why), but it works with original AZW3 file.

I added 5px white border to images using ImageMagick tools (workaround so my reader just cuts those white border and not the actual image). Additionally I adjusted size and sharpened all images, so my reader won't have to change resolution on the fly (for quality and readability). I also set a bit of negative left margins during conversion, so that the images could be a bit wider.
The code is now much more readable than in the original files provided by Amazon .

If this can be helpful for anyone, here are command line examples on how to batch change size and sharpeness:

 magick mogrify -format bmp *.jpeg    //convert every jpeg image to bmp for further loseless processing

magick mogrify -filter Mitchell -resize 550x730^> -format bmp *.bmp  //downscale images that are wider than 550px or higher than 730px, leaving smaller images untouched

magick mogrify -bordercolor white -border 5x3 -unsharp 0x1.1+2+0 -format jpeg *.bmp     //add white border and sharpeness to every bmp image and save back as jpeg

and the margins:

div span img {
 margin-left:-15px;
}

@davidfor - what do You mean by "post the code"? What code besides CSS styles can I post here? Debugger output?
I couldn't find "unpack book" feature - where is it located? This could be much faster than deleting and then uploading almost 2000 files using book editor...

[davidfor]

Originally Posted by dr_Fell

@davidfor - what do You mean by "post the code"? What code besides CSS styles can I post here? Debugger output?

The HTML code that actually puts the image in the book. There could be styles on it or something else that positions the images badly.

I couldn't find "unpack book" feature - where is it located? This could be much faster than deleting and then uploading almost 2000 files using book editor...

For me, it is on the right-click menu in the book list. But, you might need to add it using the toolbar configuration in the preferences.

[theducks]

Originally Posted by dr_Fell

@davidfor - what do You mean by "post the code"? What code besides CSS styles can I post here? Debugger output?
I couldn't find "unpack book" feature - where is it located? This could be much faster than deleting and then uploading almost 2000 files using book editor...

'U" is the shortcut, even if there is no menu item

[dr_Fell]

Indeed, I had to add this option. Also, thanks for the shortcut.