What is the right size for images in epub?

Kasper Hviid · 06-03-2013, 12:19 PM

Since ebook readers have different resolutions, I would normally aim at an oversize image which then gets scaled down in the reader. But when I tried a 2712 x 1465 jpeg, my reader simply ignored it. Given that I have a screensize of 1440 x 1080, it isn't even that much oversize.

The covers of all public domain books are low-res, like 520x800px. I can clearly see each pixel.

What is the right choice for image size in epub? What would look the best on most devices?

DaleDe · 06-03-2013, 12:51 PM

The public domain eBooks are targeted at 800 x 600 screen resolution for the most part. You should not exceed 4 Mega pixels as some devices cannot handle anything bigger. Your reader should have handled a 4 Mega pixel image I would have thought. Perhaps it was the aspect ratio that gave it trouble. I would suggest you try some other values with your reader and see how it scales things. You might just have a worst case reader. I see you sign on says you have no device.

Dale

Kasper Hviid · 06-03-2013, 01:07 PM

Sorry, I didn't feel like typing in hardware data when I registered. My device is a Kobo Aura HD. (In defence of my device, I will mention that it renders my .cbz version of SideWalk Bubblegum perfectly - and that's 2275x2333 pixels png's in 1 bit.)

You mention a max size of 4 mega pixels - will I be safe if I just keep below that, or is 'almost-4-mega-pixel' images also a risk?

I like having things working on my own reader, but what I'm after is mostly being able to produce epub files that works almost everywhere.

DaleDe · 06-03-2013, 01:24 PM

Quote:

Originally Posted by Kasper Hviid

Sorry, I didn't feel like typing in hardware data when I registered. My device is a Kobo Aura HD. (In defence of my device, I will mention that it renders my .cbz version of SideWalk Bubblegum perfectly - and that's 2275x2333 pixels png's in 1 bit.)

You mention a max size of 4 mega pixels - will I be safe if I just keep below that, or is 'almost-4-mega-pixel' images also a risk?

I like having things working on my own reader, but what I'm after is mostly being able to produce epub files that works almost everywhere.

My experience is yes you will be safe up to 4 MPixel. and probably up to the binary equivalent since memory boundaries are involved and the limit is likely due to a staging area in memory where the image is rescaled. 4,194,304 would be the upper size based on boundaries.

Kasper Hviid · 06-03-2013, 02:07 PM

Thanks, it is really helpful to have a fixed max value. Hey, I just tried 1500x810 pixels, which works! :-)

06-03-2013, 12:19 PM	#1
Kasper Hviid Zealot Posts: 141 Karma: 2784614 Join Date: Nov 2012 Device: none	What is the right size for images in epub? Since ebook readers have different resolutions, I would normally aim at an oversize image which then gets scaled down in the reader. But when I tried a 2712 x 1465 jpeg, my reader simply ignored it. Given that I have a screensize of 1440 x 1080, it isn't even that much oversize. The covers of all public domain books are low-res, like 520x800px. I can clearly see each pixel. What is the right choice for image size in epub? What would look the best on most devices?

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06-03-2013, 12:51 PM	#2
DaleDe Grand Sorcerer Posts: 11,470 Karma: 13095790 Join Date: Aug 2007 Location: Grass Valley, CA Device: EB 1150, EZ Reader, Literati, iPad 2 & Air 2, iPhone 7	The public domain eBooks are targeted at 800 x 600 screen resolution for the most part. You should not exceed 4 Mega pixels as some devices cannot handle anything bigger. Your reader should have handled a 4 Mega pixel image I would have thought. Perhaps it was the aspect ratio that gave it trouble. I would suggest you try some other values with your reader and see how it scales things. You might just have a worst case reader. I see you sign on says you have no device. Dale

06-03-2013, 01:07 PM	#3
Kasper Hviid Zealot Posts: 141 Karma: 2784614 Join Date: Nov 2012 Device: none	Sorry, I didn't feel like typing in hardware data when I registered. My device is a Kobo Aura HD. (In defence of my device, I will mention that it renders my .cbz version of SideWalk Bubblegum perfectly - and that's 2275x2333 pixels png's in 1 bit.) You mention a max size of 4 mega pixels - will I be safe if I just keep below that, or is 'almost-4-mega-pixel' images also a risk? I like having things working on my own reader, but what I'm after is mostly being able to produce epub files that works almost everywhere.

06-03-2013, 02:07 PM	#5
Kasper Hviid Zealot Posts: 141 Karma: 2784614 Join Date: Nov 2012 Device: none	Thanks, it is really helpful to have a fixed max value. Hey, I just tried 1500x810 pixels, which works! :-)

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