html2mobi (a mobigen replacement written in Perl) - Page 4

JSWolf · 11-28-2007, 05:19 PM

How about just keeping the images the same size they are?

wallcraft · 11-28-2007, 05:22 PM

GIF images in MobIPocket very definitely have a 64KB limit (actually slightly smaller than 64 KB) and I assumed that this was a PRC record size limit. If a GIF image is larger than ~64 KB, mobigen.exe, reduces its size (in pixels) until it fits in 64KB.

I don't know if larger JPEGs are allowed, or if MobiPocket just increases the lossyness(?) until it also fits in 64 KB.

See Images in MobiPocket, which includes references to MobiPocket documentation and to other threads on this issue.

tompe · 11-28-2007, 05:36 PM

Quote:

Originally Posted by JSWolf

How about just keeping the images the same size they are?

That is what I am doing now. But there is probably some issue with the format that causes 600x800 images to nor work. So therefore I had to shrink them a bit. But this problem is on the todo list.

tompe · 11-28-2007, 05:39 PM

There is a version 0.02 available at http://www.ida.liu.se/~tompe/mobiperl/

Table of contents and links works. You had to change href to a filepos to get it to work on the Gen3.

wallcraft · 11-28-2007, 09:12 PM

I took a look at my (DRM-free) LIT files converted to MOBI via ConvertLIT and mobigen.exe -jpeg. Any JPEG that was originally larger than 64 KB was reduced to less than 64 KB in the MOBI file, but the image dimensions in pixels was maintained. So I think it is the case that MOBI only allows images < 64 KB.

DaleDe · 11-29-2007, 01:19 AM

Quote:

Originally Posted by wallcraft

I took a look at my (DRM-free) LIT files converted to MOBI via ConvertLIT and mobigen.exe -jpeg. Any JPEG that was originally larger than 64 KB was reduced to less than 64 KB in the MOBI file, but the image dimensions in pixels was maintained. So I think it is the case that MOBI only allows images < 64 KB.

That is a limitation of the Palm database size, which is the fundamental Mobi format.

Dale

JSWolf · 11-29-2007, 01:57 AM

Quote:

Originally Posted by wallcraft

I took a look at my (DRM-free) LIT files converted to MOBI via ConvertLIT and mobigen.exe -jpeg. Any JPEG that was originally larger than 64 KB was reduced to less than 64 KB in the MOBI file, but the image dimensions in pixels was maintained. So I think it is the case that MOBI only allows images < 64 KB.

So Mobigen recompresses the jpeg image until it hits a physical size of 64k or less? So even if that makes the image fuzzy, it won't matter as long as the 64k limit is maintained right? That is crazy.

wallcraft · 11-29-2007, 09:44 AM

Quote:

Originally Posted by JSWolf

So Mobigen recompresses the jpeg image until it hits a physical size of 64k or less? So even if that makes the image fuzzy, it won't matter as long as the 64k limit is maintained right? That is crazy.

Yes, although many JPEGs are already smaller than 64 KB, and so far the examples I have seen don't look bad at 64 KB. For GIF images, MobiPocket instead makes the image itself smaller until it fits in 64 KB (which is a different loss in quality, arguably much worse). MobiPocket's primary legacy issue is the Palm format, but Plucker uses PDB and it allows larger images by splitting them across multiple records.

tompe · 11-29-2007, 09:52 AM

Quote:

Originally Posted by wallcraft

I took a look at my (DRM-free) LIT files converted to MOBI via ConvertLIT and mobigen.exe -jpeg. Any JPEG that was originally larger than 64 KB was reduced to less than 64 KB in the MOBI file, but the image dimensions in pixels was maintained. So I think it is the case that MOBI only allows images < 64 KB.

I will look at this because it might be that 64 KB is max if you want it to work on all devices. It might be that larger images works on the Gen3.

Do you have any good example lit file with a large image?

tompe · 11-29-2007, 09:56 AM

I also have a lit file which had a 600x800 cover image but this image was not in the manifest so mobigen will fail to us the bigger image and you will get the small image. My script searches the unpacked files for a big cover image and uses that even if it is not in the manifest. You can also specify on the command line a file to use as cover image.

tompe · 11-29-2007, 10:20 AM

Quote:

Originally Posted by tompe

I will look at this because it might be that 64 KB is max if you want it to work on all devices. It might be that larger images works on the Gen3.

I just checked. A jpg file with size 138462 works on the Gen3. But it does not work on my Palm T5. So if you generate your mobi files for a specific device you can have larger images. That might actually explain why the Kindle uses another file extension.

I will probably let my script use large files and print warnings that the file will not work on some devices and have a flag to generate mobi files with records with a max size of 64 KB.

HarryT · 11-29-2007, 10:22 AM

Quote:

Originally Posted by JSWolf

So Mobigen recompresses the jpeg image until it hits a physical size of 64k or less? So even if that makes the image fuzzy, it won't matter as long as the 64k limit is maintained right? That is crazy.

No, it's a consequence of the fact that the image has to fit into 64k. It's not really a terribly onerous limit for the type of images you tend to get in eBooks - they are generally under 64k anyway.

wallcraft · 11-29-2007, 10:34 AM

Quote:

Originally Posted by tompe

I just checked. A jpg file with size 138462 works on the Gen3. But it does not work on my Palm T5.

Was this the only image in the file? I don't know much about the PRC format, but I would expect record length violations to only work for the last record in the file.

tompe · 11-29-2007, 11:47 AM

Quote:

Originally Posted by wallcraft

Was this the only image in the file? I don't know much about the PRC format, but I would expect record length violations to only work for the last record in the file.

No, it was the first record after the compressed text that was to large. Then there were 6 records with smaller images after that. When I try to load this on my palm it says "corrupt database".

tompe · 11-29-2007, 06:57 PM

Version 0.03 is now available.

I have fixed so that all records are smaller than 64K. I resize the image data by choosing a suitable jpeg quality. If I find a real example were the image quality becomes too bad I will try to find a solution. So if anybody have a real example of a lit file where mobigen -jpeg fails to produce something that you can read I would really like to have a pointer to it.

The guide table of content now works so in FBReader I get the table of content button.

11-28-2007, 05:22 PM	#47
wallcraft reader Posts: 6,977 Karma: 5183568 Join Date: Mar 2006 Location: Mississippi, USA Device: Kindle 3, Kobo Glo HD	GIF images in MobIPocket very definitely have a 64KB limit (actually slightly smaller than 64 KB) and I assumed that this was a PRC record size limit. If a GIF image is larger than ~64 KB, mobigen.exe, reduces its size (in pixels) until it fits in 64KB. I don't know if larger JPEGs are allowed, or if MobiPocket just increases the lossyness(?) until it also fits in 64 KB. See Images in MobiPocket, which includes references to MobiPocket documentation and to other threads on this issue. Last edited by wallcraft; 11-28-2007 at 05:27 PM.

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11-28-2007, 05:19 PM	#46
JSWolf Resident Curmudgeon Posts: 79,249 Karma: 145488788 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	How about just keeping the images the same size they are?

11-28-2007, 05:39 PM	#49
tompe Grand Sorcerer Posts: 7,452 Karma: 7185064 Join Date: Oct 2007 Location: Linköpng, Sweden Device: Kindle Voyage, Nexus 5, Kindle PW	There is a version 0.02 available at http://www.ida.liu.se/~tompe/mobiperl/ Table of contents and links works. You had to change href to a filepos to get it to work on the Gen3.

11-28-2007, 09:12 PM	#50
wallcraft reader Posts: 6,977 Karma: 5183568 Join Date: Mar 2006 Location: Mississippi, USA Device: Kindle 3, Kobo Glo HD	I took a look at my (DRM-free) LIT files converted to MOBI via ConvertLIT and mobigen.exe -jpeg. Any JPEG that was originally larger than 64 KB was reduced to less than 64 KB in the MOBI file, but the image dimensions in pixels was maintained. So I think it is the case that MOBI only allows images < 64 KB.

11-29-2007, 09:56 AM	#55
tompe Grand Sorcerer Posts: 7,452 Karma: 7185064 Join Date: Oct 2007 Location: Linköpng, Sweden Device: Kindle Voyage, Nexus 5, Kindle PW	I also have a lit file which had a 600x800 cover image but this image was not in the manifest so mobigen will fail to us the bigger image and you will get the small image. My script searches the unpacked files for a big cover image and uses that even if it is not in the manifest. You can also specify on the command line a file to use as cover image.

11-29-2007, 06:57 PM	#60
tompe Grand Sorcerer Posts: 7,452 Karma: 7185064 Join Date: Oct 2007 Location: Linköpng, Sweden Device: Kindle Voyage, Nexus 5, Kindle PW	Version 0.03 is now available. I have fixed so that all records are smaller than 64K. I resize the image data by choosing a suitable jpeg quality. If I find a real example were the image quality becomes too bad I will try to find a solution. So if anybody have a real example of a lit file where mobigen -jpeg fails to produce something that you can read I would really like to have a pointer to it. The guide table of content now works so in FBReader I get the table of content button.

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