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Old 04-01-2017, 01:00 PM   #1
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Send/Save Cover in Greyscale

Hi all,

I had an Idea for a "feature" that i think would be beneficial for some of us.

Ad a checkbox that by update the "cover" transforms the Image into grey scale image.

I use to have 2x for each book a high res cover for "pdf" / high dpi Android devices but also for epub / mobi generation 800x600 and they mostly only display grey scale anyhow. by this way I reduce the ebook size from 1MB avg to 200KB, not much in single book terms but for 100 books makes up quite some effort.

\Pete
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Old 04-01-2017, 01:42 PM   #2
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Originally Posted by icq70610 View Post
Hi all,

I had an Idea for a "feature" that i think would be beneficial for some of us.

Ad a checkbox that by update the "cover" transforms the Image into grey scale image.

I use to have 2x for each book a high res cover for "pdf" / high dpi Android devices but also for epub / mobi generation 800x600 and they mostly only display grey scale anyhow. by this way I reduce the ebook size from 1MB avg to 200KB, not much in single book terms but for 100 books makes up quite some effort.

\Pete
I really think this option should be in the Send to Device setting, Not
Modify EPUB , which changes the Library Copy.
Once done COLOR is lost for good.
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Old 04-01-2017, 06:02 PM   #3
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I really think this option should be in the Send to Device setting, Not
Modify EPUB , which changes the Library Copy.
Once done COLOR is lost for good.
I concur. Also, different devices have different algorithms for translating color to grayscale, based on their own capabilities, so such a change is pretty much begging for complaints that some grayed book looks worse on whichever device.
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Old 04-01-2017, 06:11 PM   #4
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I do want to keep the cover in color. If I read the book on my phone or iPad, I want to see the cover in color. If I read the book on my H2O, the H2O can show the cover in grayscale. Also,some Readers use 16 shades of gray and some use 8. The plugin will have no idea how to best dither the cover.

Last edited by JSWolf; 04-01-2017 at 06:23 PM.
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Old 04-01-2017, 06:23 PM   #5
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I do want to keep the cover in color. If I read the book on my phone or iPad, I want to see the cover in color. If I read the book on my H2O, the H2O can show the cover in grayscale.
JS, you're free to have your preferences on every subject under the sun. Really, you are. But when the topic is whether or not to add a feature to a plugin, or modify how an existing one works, saying "I have no interest in that feature" only clutters the conversation.

That's doubly true when making an observation that has already been made and agreed with: that this particular change would fit better in the "send to device" module (changing the copy on that one device) rather than in a module that alters the archive (changing it for all future use). There is value in the idea of sending a grayscale cover to a grayscale device - primarily in that grayscale images are much more compact, so such a change would permit more books to fit on the device - so while you or I may not mind the "hit" of sending full color to such devices, it's perfectly reasonable that others would want a way to change that.

Personally, I'd love a smoother, more automatic way to use the color picker to change the cover page's background color - but I'm perfectly aware that this is a very niche desire, so there's not much to be gained by saying so. Thus, I keep my trap shut and use the existing tool to get what I'm after.

Last edited by Rev. Bob; 04-01-2017 at 06:26 PM.
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Old 04-01-2017, 06:24 PM   #6
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JS, you're free to have your preferences on every subject under the sun. Really, you are. But when the topic is whether or not to add a feature to a plugin, or modify how an existing one works, saying "I have no interest in that feature" only clutters the conversation.
You've missed my edit. Please go back and have a read.
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Old 04-01-2017, 06:33 PM   #7
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You've missed my edit. Please go back and have a read.
In your edit, you completely missed that I said the same thing - just in more general terms - in the message right above yours.

My later point remains true, though. Even a "full" 256-gray image will be a much smaller file than a true-color image of the same dimensions, so sending a gray version would raise the number of books one can store on that device by a considerable factor... probably a more significant margin than the existing resize option permits. (True color is typically encoded as either three or four 256-level channels; grayscale only uses one.)
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Old 04-01-2017, 07:04 PM   #8
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Originally Posted by icq70610 View Post
Hi all,

I had an Idea for a "feature" that i think would be beneficial for some of us.
@icq70610 - the consensus seems to be that adding this feature to the standard issue Modify plugin is not a good idea.

If Kovid doesn't want to add the functionality to Send to Device (and Save to Disk), then you could create a private version of the plugin, as a number of other folks have done.

The plugin already has the code to remove and inject cover images, so what's needed is 'a way' to create a greyscale image from the book's cover.jpg and inject that into the epub. There's a good chance that 'the way' is available from the calibre core.

I'm sure the likes of Rev. Bob and Kovid will gladly offer their guidance.

see post 1099

BR

Last edited by BetterRed; 04-01-2017 at 08:37 PM.
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Old 04-01-2017, 07:43 PM   #9
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In your edit, you completely missed that I said the same thing - just in more general terms - in the message right above yours.

My later point remains true, though. Even a "full" 256-gray image will be a much smaller file than a true-color image of the same dimensions, so sending a gray version would raise the number of books one can store on that device by a considerable factor... probably a more significant margin than the existing resize option permits. (True color is typically encoded as either three or four 256-level channels; grayscale only uses one.)
What I do with the cover is use Calibre's editor to reduce the size to 1500 lines if it's larger and I losslessly compress at 80%. That works and reduces the cover image size enough. I prefer to keep the color images. I know grayscale images are going to be smaller, but I don't try to cram my H2O full of books.
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Old 04-01-2017, 07:50 PM   #10
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I have the perfect solution. What's needed is to add an option in the Calibre editor to convert an image to grayscale. You do most things you'd want to do with an image but not convert to graycale.
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Old 04-01-2017, 08:33 PM   #11
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Why not just open the epub in Sigil, right click the cover.jpeg file, open it with any half decent image editor and save it in greyscale.

Why care if it changes the epub in the library, it doesn't change the book's cover.jpg file, which can be put back into the library epub with Polish Book in a heartbeat.

And not a line of code need be written.

BR
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Old 04-02-2017, 08:06 AM   #12
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What I do with the cover is use Calibre's editor to reduce the size to 1500 lines if it's larger and I losslessly compress at 80%. That works and reduces the cover image size enough. I prefer to keep the color images. I know grayscale images are going to be smaller, but I don't try to cram my H2O full of books.
You appear to be confusing my statement that some people do X for reasons A and B with (a) me doing X myself or (b) me recommending that you, specifically, should do X.

Neither is true.

You do what you want, and let other people do as they please. It's a big, wide world out there, full of room for lots of different opinions on this subject. It's neither your place nor mine to impose our opinions on others as The One True Way.

I do some weird stuff, for example. Having noticed how many Open Road Media books use a certain color red bar across the top and bottom of their covers, I took advantage of my newly-installed calibre developer's environment to add a code snippet to my installation that changes the cover page's background color to that shade of red if calibre detects that they're the publisher.

Will anyone else want to do that? Probably not - but I do, so I did, and I like it that way.

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Old 04-07-2017, 11:33 PM   #13
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Why not just open the epub in Sigil, right click the cover.jpeg file, open it with any half decent image editor and save it in greyscale.

Why care if it changes the epub in the library, it doesn't change the book's cover.jpg file, which can be put back into the library epub with Polish Book in a heartbeat.

And not a line of code need be written.

BR
Personally I think cover manipulation could be part of the metadata plugboard options. So just like we can massage metadata according to our needs while sending to our devices having the ability to do the same for covers might be good option.
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Old 04-08-2017, 04:11 AM   #14
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Personally I think cover manipulation could be part of the metadata plugboard options. So just like we can massage metadata according to our needs while sending to our devices having the ability to do the same for covers might be good option.
Not a good idea (IMHO) because covers are not metadata.
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Old 04-08-2017, 06:29 AM   #15
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Not a good idea (IMHO) because covers are not metadata.
I could make a rather compelling argument to the contrary, especially given how often covers change when books get reprinted.
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