Optimizing images for use in Kindle

[ProDigit]

Originally Posted by wallcraft

The "screenshots" of the Kindle are copies of the screen bitmap, so they are exactly 600x800 and the image part is exactly 525x640.

Having a screenshot capability (only currently on the iLiad and the Kindle) makes this kind of optimization much easier, because you can "measure" the screen using the screenshot and an image editor on a PC. All Desktop PCs have a screenshot capability, as does the iPhone, but if does not seem to have trickled down to most EInk devices.

I'm going to see if that resolution also is the resolution for the Sony reader.
I'm using the methode of a 'grid'.
So far I've gone from 800x600 downto 720x550 and no luck yet...
The 'perfect grid' hasn't come out yet.
I'll let you know if time permits, but I'm starting tho think that perhaps you might be right.
At least for the kindle you are.

[wallcraft]

Originally Posted by ProDigit

I'm using the methode of a 'grid'.
So far I've gone from 800x600 downto 720x550 and no luck yet...
The 'perfect grid' hasn't come out yet.

I intend to do something similar on the EZ Reader (Hanlin V3) this weekend, and since it does not have a screenshot capability I will be back to trial and error. Can you share your "grid" images, or are they easy to make? Note that in HTML and the MOBI format (at least) you can put multiple thin and tall images side by side, and this may help in telling which ones have been rescaled. Multiple thin and wide images can also similarly fit on one page.

[ProDigit]

The images I use is a B&W monochrome BMP.

I just created it in paint, unfortunately I don't have it available on this computer.
You can create it in a matter of 4 minutes.

Just create a new document in paint with 600x800 resolution.

Then draw a line on the top.
Select the drawing (CTRL + A), and copy paste it (CTRL +C, CTRL + V) 2 pixels lower (I found it works best when zooming to 200 or 400%).
Once you have 2 lines, just continue copy/pasting the whole image.
At first it seems to take long, but as soon as you have the second line correct, work goes quite fast (1 line, 2lines, 4lines, 8lines, 16, 32, 64, 128, 256, 512,..).
Should take you 12 steps.

The painfull process starts when you are going to decrease the resolution.
I save the BMP as 600x800. Then take of 1 pixel from the bottom and from the side.
Save that one as 599x799.
This process takes a lot of time, and leaves you with a lot of BMP's.
I'm still in the process (while doing other things).

Unless you got a great photo editor that can autocrop and save for you, most work will be done manual.

If you want to, I can prepare the BMP's and RAR them, but that 'll most likely not be before next week!

[ProDigit]

Okay,I have the files, sooner then expected.
They are monochrome BMP,compressed, for horizontal and vertical probing, 600x800 to 640x500.

One of them is 800x600 pix, so you can test cropping it yourself downto the resolution you prefer.

Just see which 'grids' seem to display natural.
I still have to do the test when I get home; so that'll be around tomorrow.

[falcolas]

I'm working on a tool which might help prepare images for Kindle ebooks. My one question - what is the best file format to output the images in?

The attached file is from my initial testing (using an image from this thread previously).

[FooSoft]

Originally Posted by falcolas

I'm working on a tool which might help prepare images for Kindle ebooks. My one question - what is the best file format to output the images in?

The attached file is from my initial testing (using an image from this thread previously).

Out of curiosity - what is it going to do different from my tool (http://www.foosoft.net/mangle)? Even though it's written for manga it should work for everything else...

Anyways, in terms of format I think GIF is the best option, especially when you convert to grayscale (less colors is best, get more run length for LZW compression). It doesn't have re-compression artifacts of JPG, smaller in size than PNG. The 256 color limit in the format is obviously a non-factor.

[wallcraft]

Originally Posted by falcolas

My one question - what is the best file format to output the images in?

See MobiPocket's Image support and display. This says that 63KB is the maximum filesize for JPEG as well as other formats, but that isn't the case any more. The bottom line is that if you use JPEG you don't need to worry about image file size, otherwise it still needs to be less than 63KB. The downside of JPEG is that it is a lossy format, which suggest that line drawings and images of text should be GIFs. Hopefully these will be less than 63KB in size (otherwise MobiPocket's tools will convert it to JPEG when making the MOBI).

Note that Calibre (mobi2oeb) converts all images to JPEG when format shifting MOBIs.

[falcolas]

Originally Posted by FooSoft

Out of curiosity - what is it going to do different from my tool (http://www.foosoft.net/mangle)? Even though it's written for manga it should work for everything else...

Nothing. Just the first mention I saw of your tool, and I was basing my work off a perceived need in this thread (and a hankering to play with dithering algorithms). In fact, it will do less, since it will just make the necessary resize and color reduction - it won't attempt to create it's own book.

Thanks for the responses!

[ProDigit]

Gifs are probably better for animes and books with little colors/details.
Once you start talking about 'Storm', 'Trigie', or other highly detailed comic books, which near to photo quality Jpeg will be better.
Textbooks are probably best compressed in either GIF, TIFF, or PNG.

[tompe]

Originally Posted by wallcraft

See MobiPocket's Image support and display. This says that 63KB is the maximum filesize for JPEG as well as other formats, but that isn't the case any more. The bottom line is that if you use JPEG you don't need to worry about image file size, otherwise it still needs to be less than 63KB.

If the file should work on all devices the data have to be reduced to under 63KB (or maybe 61). If you meant that jpg can always be reduced to the correct size then I think that depend on the tool you use.

[beagley@alma.edu]

As a new Kindle user, I have a more basic question about images. How do you get Kindle to display jpg files. The documentation says they will work, but when I load them to document folder, they don't show up in the index. . . . Or is it the case that images can be displayed only if they are part of a Kindle format book?

[davebaxter]

Originally Posted by beagley@alma.edu

As a new Kindle user, I have a more basic question about images. How do you get Kindle to display jpg files. The documentation says they will work, but when I load them to document folder, they don't show up in the index. . . . Or is it the case that images can be displayed only if they are part of a Kindle format book?

If you're uploading directly to your kindle, you have to put all images, jpegs or otherwise, into a zip folder and then upload the zip folder. Then whatever you name the zip will show up on your home page. Select it and rifle through your jpegs at your leisure.

[kevindorsey]

Originally Posted by davebaxter

If you're uploading directly to your kindle, you have to put all images, jpegs or otherwise, into a zip folder and then upload the zip folder. Then whatever you name the zip will show up on your home page. Select it and rifle through your jpegs at your leisure.

Damn, that's a helluva late response...

[sirbruce]

Actually, I never knew .zip files would work. The way I do it is just create a dirctory under the pictures directory, and the image files in that new directory. The "book" will be named whatever the directory is named.

[davebaxter]

Originally Posted by kevindorsey

Damn, that's a helluva late response...

Yeeeaaahhh...sorry. I was (rather obviously) not looking at the dates on this forum as I was reading through it front-to-back. I noticed the date right after I posted. Thought: "Oh, well, hope someone else finds it useful!". This sucker comes up pretty high in Google when you search for "Kindle" and "Optimize images" so I was hoping it got readership, even if only dunces like moi actually bother to post in the damn thing
--Dave B.