Mobileread
Need your help: screenshots from your e-reader
#11  willus 12-28-2014, 11:22 AM
Quote Ravensknight
What does " get precise viewable PDF screen dimensions for the readers for software applications" actually mean? and what does it mean for you?

Just curious what you're trying accomplish here, specifically...
Knowing the precise viewing resolution allows the generation of bitmapped PDFs that exactly match the viewing screen, pixel for pixel, so that they don't have to be re-sized by the reader.
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#12  willus 12-28-2014, 11:23 AM
Quote GeoffR
Sorry, I just realised that a patch I have to reduce the epub footer size on my Glo affects the footer in the pdf reader too, so the first set of screenshots in the post above won't be typical. (The full-screen shots will be the same on all Glos though.) I never read pdfs on my Glo, so I'm not very familiar with the pdf reader.

Now that I know that the footer size in the pdf reader is the same as in the epub reader, it is easy to calculate the viewable area for pdfs on all current (unpatched) Kobo models:
Code
 Model Full-screen mode Normal mode
------- ---------------- -----------
Touch 600x800 600x730
Mini 600x800 600x730
Glo 758x1024 758x942
Aura SD 758x1014 758x932
Aura HD 1080x1440 1080x1320
H2O 1080x1429 1080x1309
Very helpful! Thank you for educating me about Kobo models.
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#13  willus 12-28-2014, 11:25 AM
Quote JSWolf
Then you look at the resolution of just the image on the Voyage screen grab, it comes out to be 852x1365.

I'll have to try this later on my H2O to see what resolution I get as I have a very small footer defined with almost no space wasted above the footer.
FYI, you have to look at both screen shots. The 852 pixels doesn't mean anything because that checkerboard is taller than it is wide, so the reader is fitting it to the maximum viewable pixel height. The other image is wider than it is tall, so it fits to the maximum viewable pixel width of the device.
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#14  Doitsu 12-28-2014, 02:08 PM
Please find attached the screenshots taken with my Kindle Paperwhite 2.
KindlePW2_1.png KindlePW2_2.png 
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#15  JSWolf 12-29-2014, 06:40 PM
Here are the two screenshots from my Kobo Aura H2O.
screen_002.png screen_001.png 
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#16  willus 12-29-2014, 08:29 PM
Quote JSWolf
Here are the two screenshots from my Kobo Aura H2O.
Thank you. 1080 x 1386. So indeed, you have little wasted space. Do you know why there is a small black strip at the top of the screen shots? Is that something which can be customized? Can the footers on Kobos be adjusted to whatever size one desires and/or do you have to "hack" them to do so?
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#17  JSWolf 12-29-2014, 09:16 PM
Quote willus
Thank you. 1080 x 1386. So indeed, you have little wasted space. Do you know why there is a small black strip at the top of the screen shots? Is that something which can be customized? Can the footers on Kobos be adjusted to whatever size one desires and/or do you have to "hack" them to do so?
It just comes out as black in the screenshot. It's just a small amount of space at the top that's not used. ON the screen, it's just blank with a normal background.

I'll have to ask about it and see if it can be changed.

I've noticed something about the screenshots. The screenshots from the Kobo Readers have more accurate coloring then the Kindles.
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#18  willus 12-30-2014, 01:14 PM
Quote JSWolf
I've noticed something about the screenshots. The screenshots from the Kobo Readers have more accurate coloring then the Kindles.
I hadn't intended this as a test of the grayscale conversion algorithm in the devices, but it certainly is interesting. The checkerboard pattern I put in the PDF is full (100%), either red, green, or blue. The Kobos convert the red, green, and blue to 52%, 86%, and 26% of full white, respectively. The Kindle 2 converts to 50%, 33%, and 17%, respectively, and the PW2/Voyage convert to 9%, 35%, and 12%, respectively. Interestingly, none of these match the commonly used grayscale conversion ITU-R BT.709 or BT.601, which are 21%,72%,7% and 30%,59%,11%, respectively, but the Kobos are definitely closest, proportionally, which explains why they look more natural. It is particularly strange to me that all of the Kindles weight the RGB components significantly differently than the ITU-R weightings (K2 has red weighted the highest, and PW2/Voyage have blue weighted more heavily than red). That seems clearly flawed, and would be trivial to correct. How odd.
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#19  KaiReader 12-30-2014, 09:16 PM
are you only interested in dedicated e-readers? I have a couple of Samsung tablets if you're after those also
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#20  DaleDe 12-31-2014, 01:31 PM
Quote willus
I hadn't intended this as a test of the grayscale conversion algorithm in the devices, but it certainly is interesting. The checkerboard pattern I put in the PDF is full (100%), either red, green, or blue. The Kobos convert the red, green, and blue to 52%, 86%, and 26% of full white, respectively. The Kindle 2 converts to 50%, 33%, and 17%, respectively, and the PW2/Voyage convert to 9%, 35%, and 12%, respectively. Interestingly, none of these match the commonly used grayscale conversion ITU-R BT.709 or BT.601, which are 21%,72%,7% and 30%,59%,11%, respectively, but the Kobos are definitely closest, proportionally, which explains why they look more natural. It is particularly strange to me that all of the Kindles weight the RGB components significantly differently than the ITU-R weightings (K2 has red weighted the highest, and PW2/Voyage have blue weighted more heavily than red). That seems clearly flawed, and would be trivial to correct. How odd.
Fascinating information. I will add it to our wiki. Thanks.
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