Save the cover as an image file when loading a document

[pazos]

Originally Posted by Winkelschraube

Wow pazos, that would be awesome. I thank you already. With my Poke 2 the folder "/Pictures" and the file is best "bookcover.png". So together "/Pictures/bookcover.png".

I will certainly take a look at it and learn something from it to understand how it works and to be able to make future adjustments myself.

Minimum changes are:

--- a/frontend/apps/reader/readerui.lua
+++ b/frontend/apps/reader/readerui.lua
@@ -555,6 +555,11 @@ function ReaderUI:doShowReader(file, provider)
         })
         self:showFileManager()
         return
+    else
+        local image = document:getCoverPageImage()
+        if image then
+            Device.screen.bb:writePNG("/home/pazos/Escritorio/test2.png", false, image)
+        end
     end
     if document.is_locked then
         logger.info("document is locked")

and

--- a/ffi/blitbuffer.lua
+++ b/ffi/blitbuffer.lua
@@ -1760,7 +1760,7 @@ write blitbuffer contents to a PNG file
 @param filename the name of the file to be created
 --]]
 local Png  -- lazy load ffi/png
-function BB_mt.__index:writePNG(filename, bgr)
+function BB_mt.__index:writePNG(filename, bgr, buffer)
     if not Png then Png = require("ffi/png") end
     local hook, mask, _ = debug.gethook()
     debug.sethook()
@@ -1770,7 +1770,8 @@ function BB_mt.__index:writePNG(filename, bgr)
     for y = 0, h-1 do
         local offset = 4 * w * y
         for x = 0, w-1 do
-            local c = self:getPixel(x, y):getColorRGB32()
+            local c = buffer and buffer:getPixel(x, y):getColorRGB32() or
+                self:getPixel(x, y):getColorRGB32()
             -- NOTE: Kobo's FB is BGR(A), we already trick MuPDF into doing it that way for us, so, keep faking it here!
             if bgr then
                 mem[offset] = c.b

give it a try on the emulator with some books (replace "/home/pazos/Escritorio/test2.png" with the path you want). If you're fine with the changes you can move them to android.


Probably the 2nd block of code can be upstreamed, because it doesn't affect current code in any way and is just a quick way of writting a png file from a memory buffer without having to write to the framebuffer first.

[NiLuJe]

@pazos: The second hunk does make sense, but it's missing getting the width/height from buffer, too, because right now it uses the image buffer but with the framebuffer's dimensions .

(Which I realize may be the point, but then what happens if image buffer's dimension != framebuffer's dimension?)

[Winkelschraube]

Thank you very much. I see this eventing.

[pazos]

Originally Posted by NiLuJe

@pazos: The second hunk does make sense, but it's missing getting the width/height from buffer, too, because right now it uses the image buffer but with the framebuffer's dimensions .

(Which I realize may be the point, but then what happens if image buffer's dimension != framebuffer's dimension?)

It seems that I was lucky on my tests. A "cover" that doesn't match framebuffer dimension is attached.

And the proper code, as suggested, would be:

--- a/ffi/blitbuffer.lua
+++ b/ffi/blitbuffer.lua
@@ -1760,17 +1760,19 @@ write blitbuffer contents to a PNG file
 @param filename the name of the file to be created
 --]]
 local Png  -- lazy load ffi/png
-function BB_mt.__index:writePNG(filename, bgr)
+function BB_mt.__index:writePNG(filename, bgr, buffer)
     if not Png then Png = require("ffi/png") end
     local hook, mask, _ = debug.gethook()
     debug.sethook()
-    local w, h = self:getWidth(), self:getHeight()
+    local w = buffer and buffer:getWidth() or self:getWidth()
+    local h = buffer and buffer:getHeight() or self:getHeight()
     local cdata = C.malloc(w * h * 4)
     local mem = ffi.cast("char*", cdata)
     for y = 0, h-1 do
         local offset = 4 * w * y
         for x = 0, w-1 do
-            local c = self:getPixel(x, y):getColorRGB32()
+            local c = buffer and buffer:getPixel(x, y):getColorRGB32() or
+                self:getPixel(x, y):getColorRGB32()
             -- NOTE: Kobo's FB is BGR(A), we already trick MuPDF into doing it that way for us, so, keep faking it here!
             if bgr then
                 mem[offset] = c.b

[Winkelschraube]

Ok it works!!11! WOOHOO.

(Don't you really want to add this as an option? Calibre Companion should be able to do that as well. And KOReader is very much better )

But I have to build "./kodev release --debug android". I don't have a Google account to sign by myself. The file is very big and loading is very slow.

I still have one problem, the image on the Poke 2 screensaver is scaled to screen size. If the width of the cover image is very small, it will be cut off at the top and bottom because it will be scaled until it is full screen.

Is there an option to adjust the background of the image to the screen ratio?

[Winkelschraube]

Pictures of the scaling problem attached.

[pazos]

Originally Posted by Winkelschraube

(Don't you really want to add this as an option? Calibre Companion should be able to do that as well. And KOReader is very much better )

Nope. This is a hack. PR are welcome but will take a bit more code than that. Also it is pretty easy to migrate stuff once after an update: see https://github.com/koreader/koreader...362eeee0fd87bf

Originally Posted by Winkelschraube

But I have to build "./kodev release --debug android". I don't have a Google account to sign by myself. The file is very big and loading is very slow.

You just need to sign it, you don't need a google account. There are plenty of online tutorials for that.

Originally Posted by Winkelschraube

I still have one problem, the image on the Poke 2 screensaver is scaled to screen size. If the width of the cover image is very small, it will be cut off at the top and bottom because it will be scaled until it is full screen.

Is there an option to adjust the background of the image to the screen ratio?

No with these changes. I'm afraid you'll need to rescale the image before calling writePNG.

[Winkelschraube]

Originally Posted by pazos

No with these changes. I'm afraid you'll need to rescale the image before calling writePNG.

I don't want to scale, I want to change the background of the image to keep the aspect ratio of the screen.

I was thinking about an imagemagic script that runs in the background and checks every 30 minutes if the image has been rewritten. Because I have no idea about Lua. But of course it is better to do it in KOReader, I will try it in the next weeks.


Thanks a lot for your help so far. This is really great.

[elvvis]

Originally Posted by Frenzie

Parts of it would be theoretically quite simple, such as writing whatever you want as the screensaver to a file. But as @pazos said it's not quite clear to me if this isn't too low-level and device specific in a way that would require running the program as root. Please see https://github.com/koreader/koreader/issues/5732

This would be a great solution for a rooted Android e-Ink reader.
You would need an option for the screensaver so that the image can be saved in a certain format (jpg or png) in a user defined directory.
In the local KOReader installation you would only have to activate the screensaver in android/device.lua.

[Winkelschraube]

I removed the hack three weeks ago.
It did not work, whenever I clicked on a book in the file manager, KOReader started loading and eventually stopped. (I checked with "adb logcat".) When I tapped on the top of the screen, it finished loading (re-rendered the font each time). The image was also created. It worked fine when the Poke 2 was loaded with a USB cable. I did not notice any differences with adb.

Now I only changed the picture name in "screenshoter.lua" in line 42 to "screenshot.png" without date. So I just take a screenshot at the beginning of each book and that is the new screensaver.

self.screenshot_fn_fmt = screenshots_dir .. "screenshot.png"

But thank you all for your help and work. It was an honor for me.

[Winkelschraube]

Originally Posted by Winkelschraube

Now I only changed the picture name in "screenshoter.lua" in line 42 to "screenshot.png" without date. So I just take a screenshot at the beginning of each book and that is the new screensaver.

self.screenshot_fn_fmt = screenshots_dir .. "screenshot.png"

At 2020.10 I have to do the same in https://github.com/koreader/koreader...iewer.lua#L661