9

My goal is to produce files which, when displayed, are rendered 1:1, pixel-for-pixel, in order to ensure maximum text clarity. The values provided in the GUI version of the k2pdfopt program, seem to be incorrect, and produce an obviously degraded result when displayed on the device.

Of course, this should exclude the chrome at the bottom of the screen, and any margins that are drawn. Also, a means of preventing the software from automatically scaling the image would be useful to know.

Improve this question
2
  • To test if a bitmap image is resized you can use a 1-pixel checker pattern like this one: protie.sweb.cz/checkerboard_1920_1080.gif Resizing will probably show an aliasing artefacts. You can see the possible resulting effect on the fourth example image on this page: lagom.nl/lcd-test/clock_phase.php
    – pabouk - Ukraine stay strong
    Commented Aug 9, 2015 at 0:52
  • What do people who want to increase the font size so that they can read the file do? It is not pixel accuracy that make things easier to read.
    – mmmmmm
    Commented Nov 24, 2016 at 11:05

3 Answers 3

Reset to default
1

To prevent the images from scaling you should set the width of the image in pixels rather than in, eg, 100%. It appears that the Kindle Paperwhite is 4.6 inches wide at 212 ppi (source), which comes to an unlikely 975.2 pixels wide—but it's a place to start. I would suggest setting image width (or width of containing div) to 970 px for starters. If it's distorted, then there is probably a hard-coded margin for the page of greater than 2 pixels, so reduce a small amount and try again.

Note that specifying the pixel size will mean that on other Amazon devices, the image will not resize to fit the screen—iPad and iPhone Kindle app users may not be happy with the end result.

Improve this answer
1
  • 1
    >Kindle Paperwhite is 4.6 inches wide at 212 ppi (source), which comes to an unlikely 975.2 pixels wide ---- This is almost certainly incorrect. I'm just looking for the final figure. According to various sources the full resolution of the display is either 768x1024 or 758x1024. k2pdfopt v.2.32 gives 758x940
    – pgay
    Commented May 5, 2015 at 4:22
0

Calibre lists the paperwhite as having a pixel count of 658 x 940 and the paperwhite 3 as having a screen size of 1072 x 1430.

Improve this answer
0

Screen shots from a Paperwhite 2 displaying a PDF file can be located here. These screen shots were the basis for the values used in the latest version of k2pdfopt. My experience is that getting a 1-to-1 isn't trivial. I had to work at it with my old Kindle 2. You may need to adjust slightly the values of the width and height and the values used by the -pad option. Also you should use the -mc option (on by default). For each trial, you should take a screen shot of your PDF on your Kindle and see if it exactly matches the bitmapped file within it.

You can see the values used for the Paperwhite 2 selection by running:

k2pdfopt -dev ?
Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.