Calibre error "Cannot operate on null QImage"

[zzombie]

It was working fine till i tried adding a cover which was not a valid jpg file
and since then it is giving me error
i get the following error when i click the "generate cover" icon

ValueError: Cannot operate on null QImage

please help me get back the cover of my choice on the books.

i get the following text on error

calibre 2.84 embedded-python: True is64bit: False
Windows-7-6.1.7600 Windows ('32bit', 'WindowsPE')
('Windows', '7', '6.1.7600')
Python 2.7.9
Windows: ('7', '6.1.7600', '', 'Multiprocessor Free')
Successfully initialized third party plugins: K4PC, K4Mac, Kindle Mobi and Topaz DeDRM (0, 3, 7) && Inept Epub DeDRM (0, 1, 7) && Inept PDF DeDRM (0, 1, 4) && Generate Cover (1, 5, 21) && Ignoble Epub DeDRM (0, 1, 6) && eReader PDB 2 PML (0, 0, 5)
Traceback (most recent call last):
File "calibre_plugins.generate_cover.action", line 65, in _generate_cover
File "calibre_plugins.generate_cover.dialogs", line 1377, in __init__
File "calibre_plugins.generate_cover.dialogs", line 1669, in display_preview
File "calibre_plugins.generate_cover.draw", line 330, in generate_cover_for_book
File "calibre_plugins.generate_cover.draw", line 178, in create_cover_page
File "site-packages\calibre\utils\magick\legacy.py", line 117, in compose
File "site-packages\calibre\utils\img.py", line 246, in overlay_image
ValueError: Cannot operate on null QImage


P.S i guess its a cover generator plugin error.

[BetterRed]

Originally Posted by zzombie

It was working fine till i tried adding a cover which was not a valid jpg file
and since then it is giving me error
i get the following error when i click the "generate cover" icon

please help me get back the cover of my choice on the books.

@zzombie - try this, open the book folder and delete cover.???, then drag and drop a valid jpg into the Book Detail panel in the right sidebar.

How did you add the invalid jpg, that's where the error should have been picked up?

BR

[zzombie]

Originally Posted by BetterRed

@zzombie - try this, open the book folder and delete cover.???, then drag and drop a valid jpg into the Book Detail panel in the right sidebar.

How did you add the invalid jpg, that's where the error should have been picked up?

BR

the folder you said now has a valid jpg file.. but i still deleted everything and tried again but no success.. the file i initially tried to added wasnt downloaded properly and gave error ..since then it is giving same error inspite of uninstalling and installing again. and no matter what my covers are not showing in kindle ..the MBP1 and MBS are not showing/created by kindle in sdr folder of the book.

[BetterRed]

Can you see the valid jpg in book details viz:



If you can see it, then I think you need to 're-upload' the book to your Kindle. But that's not something I can help you with as I don't own a Kindle.

BR

[kovidgoyal]

You should post this in the generate cover plugin thread as it is an error in that plugin, not calibre itself.

[zzombie]

Thankyou @Kovidgoyal and BetterRed. i searced the generate cover plugin thread and found my answer..now the plugin is working like charm
thankyou for your help

[HRR]

I have exactly the same problem, from the same cause. I find a lot of plugin threads. Please tell me how to find the thread with the answer. Thank you.

[JSWolf]

Originally Posted by HRR

I have exactly the same problem, from the same cause. I find a lot of plugin threads. Please tell me how to find the thread with the answer. Thank you.

Have a look in the Generate Cover thread.

https://www.mobileread.com/forums/sh...d.php?t=124219

[BetterRed]

Originally Posted by HRR

I have exactly the same problem, from the same cause. I find a lot of plugin threads. Please tell me how to find the thread with the answer. Thank you.

Index of plugins

That index is one of the Sticky threads at the top of the Plugins subforum.

BR

[HRR]

Found it, fix worked perfectly, and all is well. Thank you all.

[JSWolf]

Originally Posted by BetterRed

Index of plugins

That index is one of the Sticky threads at the top of the Plugins subforum.

BR

Index of Calibre Plugins

Can that list be updated so it shows the latest version of Calibre they work with? It's listed what the earliest version is, but not what the latest version. I would list them as Calibre 6 if they work inder Calibre 6.x and same with Calibre 5, etc.

[jhowell]

Originally Posted by JSWolf

Index of Calibre Plugins

Can that list be updated so it shows the latest version of Calibre they work with? It's listed what the earliest version is, but not what the latest version. I would list them as Calibre 6 if they work inder Calibre 6.x and same with Calibre 5, etc.

While it is relatively easy to know which older calibre versions will support a particular plugin release, determining whether later calibre versions are compatible is pretty much a manual process. Are you volunteering to keep that information up to date?

I do think that it would be a good idea to eventually drop plug-ins from that list if they no longer work with recent calibre versions and are not being maintained by anyone.

[JSWolf]

Originally Posted by jhowell

While it is relatively easy to know which older calibre versions will support a particular plugin release, determining whether later calibre versions are compatible is pretty much a manual process. Are you volunteering to keep that information up to date?

I could go through the plugins thread and the list and see what's said in the threads as to what version. I would hope that info would be in the first post of the thread. If that info is not there, then they can be labeled as unknown for the latest Calibre version.

I do think that it would be a good idea to eventually drop plug-ins from that list if they no longer work with recent calibre versions and are not being maintained by anyone.

I think any plugin that won't work with Calibre 4 or later should go. I also think the plugin system should be modified so that you do not get show plugins that will not work with the Calibre version you are running.

[theducks]

Preferences: Get Plugins
Greys incompatible PI (it also provides a direct link to the dedicated thread for the selected PI)
This path does NOT support other ways (not in the index) to get plugins (lookin at you deDRM )

[BetterRed]

Originally Posted by JSWolf

Index of Calibre Plugins

Can that list be updated so it shows the latest version of Calibre they work with? It's listed what the earliest version is, but not what the latest version. I would list them as Calibre 6 if they work inder Calibre 6.x and same with Calibre 5, etc.

It's in the first post, and in the plugin code (which is what the Plugin Updater uses). When it was in the index it wasn't always maintained. So, because it served no operational purpose it was removed. Maintaining the same information in multiple places is generally regarded as poor design - or it was when I studied what came to be called software engineering in the 1960s.

If you want to volunteer to maintain the index, I'm sure that can be arranged.

BR