Images on calibre

[=X=]

Hi All,
This is something I've been meaning to ask for some time. Is there a way to make images larger in calibre. I've notice that any format (LRF/MOBI/LIT) tends to compress and reduce the images size of the embedded imgaes on the eBook, this make the images almost impossible to read. Is there a switch/setting that allows one to maximize the image or just to leave the size as is?

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[kovidgoyal]

calibre only resizes imaes to make them fit in the availale screen space of the target device.

[=X=]

Okay I've read my post and it looks like I'm asking to increase the size larger than the original.

What I really mean is can I avoid the image reduction imposed by calibre. The images always seemed to be smaller than the original.

Do you use a 72dpi when converting images to LRF/MOBI?

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[kovidgoyal]

the dpi used depends on the profile used while converting. IIRC none of the profiles have a DPI lower than 96. Again, calibre does not reduce image size below the screen size of the target device. I don't really see a point in allowing images to be bigger than this, since they would be resized on the target device anyway

[=X=]

No the issue is not that I'm asking for a bigger image than the screen, the issue is that the images are reduced too small to read on the screen. An image that is say 80mm in width seems to get reduced down to 60mm. It's hard enough to read text on the original image but the reduction makes it near impossible.

[kovidgoyal]

Again, if calibre didn't resize the image, the device would, so what do you gain by having calibre not resize the image?

[=X=]

Hmm...
Okay let me approch this another way.

What I would like to do is create a book where the format is like so.

<page break>
image (110mm by 80mm)
<page break>

Where the image has been manually created to take up most of the screen but not all.
When I create the LRF/LIT/MOBI file the image is much smaller than 110mm by 80mm.

How can I create an image that takes up most of the screen size?
What I usually get is an image that is much smaller than my original

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>


But this problem is not unique to hand creating files. This happens on any book calibre transforms.

I have a book Intelligent Investors by Benjamin Graham. I have it in MOBI/LRF/PDF format. The LRF was created by calibre. While I prefer reading the LRF, I had to on many occasions switch to the PDF so I could view the charts(an image)/images.

As you can see it was not a SONY issue since the charts/images where viewable in the PDF format.

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[JSWolf]

The chances are that the images are small in the Mobipocket edition. Use mobi2oeb to have a look. Also if you find this to be true, cut them out of the PDF (screen grab) and replace the extracted images with the larger images and then see what Calibre does with them. You'll have to use html2lrf and the --use-spine option on the opf file.

[kovidgoyal]

The way the SONY reader displays images in PDF is different from the way it displays them in LRF. You can see an example of a near full screen image in an LRF in the html2lrf demo at http://calibre.kovidgoyal.net/downloads

html2lrf will not allow for the creation of fullscreen images since it preserves margins and headers

[JSWolf]

Originally Posted by kovidgoyal

html2lrf will not allow for the creation of fullscreen images since it preserves margins and headers

But if I have my margins set to 0 all around and no headers, then will I get a fullscreen image if the image is large enough?

[=X=]

Originally Posted by JSWolf

The chances are that the images are small in the Mobipocket edition. Use mobi2oeb to have a look. Also if you find this to be true, cut them out of the PDF (screen grab) and replace the extracted images with the larger images and then see what Calibre does with them. You'll have to use html2lrf and the --use-spine option on the opf file.

Jon thanks for the tips.

The MOBi has two image. Well actuall the MOBI HTML reduced the images size in the HTML by a % to fit in the mobi reader client, but the actual size of the images is kept, even if it is larger than the screen size.

The Mobipocket clients Windows/Blackberry have an image viewer application that comes along with the MobiPocket reader. When the images is selected the image view is launched. Within the image view the reader can pan zoom and really view the image, even on a cell phone.


With MOBI created files the images are reduced this makes the image viewer usless.

Originally Posted by kovidgoyal

The way the SONY reader displays images in PDF is different from the way it displays them in LRF. You can see an example of a near full screen image in an LRF in the html2lrf demo at http://calibre.kovidgoyal.net/downloads

html2lrf will not allow for the creation of fullscreen images since it preserves margins and headers

Sure I'll look at the demo.

I guess from your explanation the only thing I cannot grasp is why programs like PDFLRF and PDFRead display images just fine. They take up the full screen.

I guess what I am trying to figure out is
1) Does calibre ALWAYS reduce the image, (this is what I am seeing)
2) Does calibre only reduce the image if it is bigger than the screen.

If it's the latter then I wounder if its a DPI issue. Does the SONY reader have a higher DPI than the PC?

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[JSWolf]

From what I gather, Calibre reduces the images (if they are large enough) to fit in the space left after the margins and header are taken into account.

So try the following... set all the margins to 0 and no header and make sure you have an image larger then 600x800 and see what you get from a conversion.

[kovidgoyal]

Originally Posted by =X=

I guess from your explanation the only thing I cannot grasp is why programs like PDFLRF and PDFRead display images just fine. They take up the full screen.

Because they set margins and headers etc to 0.

I guess what I am trying to figure out is
1) Does calibre ALWAYS reduce the image, (this is what I am seeing)
2) Does calibre only reduce the image if it is bigger than the screen.

If it's the latter then I wounder if its a DPI issue. Does the SONY reader have a higher DPI than the PC?

=X=

calibre only reduces an image if one of ots dimensions is larger than the corresponding dimension of the taget device screen in portrait orientation. The DPI of the SONY reader is ~180 while of the computer is ~100

[=X=]

Okay I can identified the problem. It seems DPI does cause problems. When I changed the DPI from 300 to 72 the image filled the screen. I wonder if what I was seeing applied to other professional eBooks.

Thanks kovid/jon
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