Adding covers

Sweetpea · 12-01-2010, 06:36 AM

Whenever I add a cover to a book, using Calibre, it creates a cover.jpg in the same folder as the book (so far so good). But when I want to add this cover to my own sources (from which I generate my books), I always get an error in the LaTeX process (dimensions too large).

It took me some time to figure this one out, but it turns out that the cover.jpg has a resolution of 1 pixel per inch... Is there a reason for this? (the original had a normal resolution, around 70 pixels per inch...)

itimpi · 12-01-2010, 08:31 AM

I have had a look at some of my books, and most of them seem to be set to 96 dpi. However I did find some set to the 1dpi value you mentioned. I could not see if this related to the version of calibre used to create the files or some other cause. I am wondering if perhaps it is something like it varies between the case where the cover is downloaded and when it is extracted from an exiting book.

I suspect in most places within Calibre it is only interested in the width/height in pixels of the cover, and does not pay any attention to the dpi value so that what it is set to has not mattered

Sweetpea · 12-01-2010, 08:58 AM

Most applications don't mind

But MikTex does... It tries to determine the size (in actual measurements, not pixels) of the file and because it's a bit too large (600x800 image, 1dpi is 600x800 inch!) it'll give an error.

And yes, it only happens when you drag it into Calibre, instead of updating the cover using the book.

kovidgoyal · 12-01-2010, 10:54 AM

there is no code in calibre to manipulate the dpi stored in jpegs. In fact, I wasn't even aware that jpegs could store dpi. What would be the point of storing dpi in raster format?

chaley · 12-01-2010, 11:38 AM

Quote:

Originally Posted by kovidgoyal

there is no code in calibre to manipulate the dpi stored in jpegs. In fact, I wasn't even aware that jpegs could store dpi. What would be the point of storing dpi in raster format?

It is used for deciding how to 'display' images on devices with differing resolutions while maintaining the same physical size. For example, when photoshop prints a 5x7 photo, it will be 5x7 no matter the printer resolution and no matter the paper size (as long as the paper is larger than 5x7).

kovidgoyal · 12-01-2010, 11:41 AM

That's just wrong

12-01-2010, 06:36 AM	#1
Sweetpea Grand Sorcerer Posts: 9,707 Karma: 32763414 Join Date: Dec 2008 Location: Krewerd Device: Pocketbook Inkpad 4 Color; Samsung Galaxy Tab S6	Adding covers Whenever I add a cover to a book, using Calibre, it creates a cover.jpg in the same folder as the book (so far so good). But when I want to add this cover to my own sources (from which I generate my books), I always get an error in the LaTeX process (dimensions too large). It took me some time to figure this one out, but it turns out that the cover.jpg has a resolution of 1 pixel per inch... Is there a reason for this? (the original had a normal resolution, around 70 pixels per inch...)

12-01-2010, 08:31 AM	#2
itimpi Wizard Posts: 4,552 Karma: 950151 Join Date: Nov 2008 Device: Sony PRS-950, iphone/ipad (Marvin/iBooks/QuickReader)	I have had a look at some of my books, and most of them seem to be set to 96 dpi. However I did find some set to the 1dpi value you mentioned. I could not see if this related to the version of calibre used to create the files or some other cause. I am wondering if perhaps it is something like it varies between the case where the cover is downloaded and when it is extracted from an exiting book. I suspect in most places within Calibre it is only interested in the width/height in pixels of the cover, and does not pay any attention to the dpi value so that what it is set to has not mattered Last edited by itimpi; 12-01-2010 at 08:37 AM.

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12-01-2010, 08:58 AM	#3
Sweetpea Grand Sorcerer Posts: 9,707 Karma: 32763414 Join Date: Dec 2008 Location: Krewerd Device: Pocketbook Inkpad 4 Color; Samsung Galaxy Tab S6	Most applications don't mind But MikTex does... It tries to determine the size (in actual measurements, not pixels) of the file and because it's a bit too large (600x800 image, 1dpi is 600x800 inch!) it'll give an error. And yes, it only happens when you drag it into Calibre, instead of updating the cover using the book.

12-01-2010, 10:54 AM	#4
kovidgoyal creator of calibre Posts: 43,858 Karma: 22666666 Join Date: Oct 2006 Location: Mumbai, India Device: Various	there is no code in calibre to manipulate the dpi stored in jpegs. In fact, I wasn't even aware that jpegs could store dpi. What would be the point of storing dpi in raster format?

12-01-2010, 11:41 AM	#6
kovidgoyal creator of calibre Posts: 43,858 Karma: 22666666 Join Date: Oct 2006 Location: Mumbai, India Device: Various	That's just wrong

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