reset 'lossless' transformation

[wassermann]

first of all i want to thank you for this very fine software!!!

I like it a lot, i never understood, what kind of dirty software big camera producers like canon can make...

now my question:
in the image viewer i've rotated some pictures, and there came up the dialog prompt that there is no lossless transformation possible. I confirmed to 'yes, make it lossless' and also confirmed 'dont ask again' (sorry, when the prompts aren't spelled correct, I'm using the german translation of the software).

now I've seen that my pictures increased in size a lot (80kB -> 400KB each). I want to reset the above mentioned flag, but dont find it somewhere...

can anybody help me?

many tia
walter

[nabocorp]

Hello,

the increase in size is normal. You camera may compress JPEG files a lot resulting in small file size (80K). When you cannot perform a lossless rotation cam2pc has to decompress the JPEG image, rotate the pixels and then recompress the JPEG image using a new compression factor. By default the compression factor of cam2pc is 15 (quality=85) resulting in nicer images but bigger. The problem is that once an image has been compressed at say 20, you cannot get back the lost quality by compressing it at 90...

To reset your answer display the options and then then Miscellaneous section. There you should have a "Reset prompt" button. Simply click it and cam2pc should ask you again...

Regards,
nabocorp

[airflow]

Hello nabocorp,

may I ask you a question? What do you mean with

[...] When you cannot perform a lossless rotation cam2pc has to decompress the JPEG image, rotate the pixels and then recompress the JPEG image using a new compression factor. [...]

?

How can it be that a lossless rotation is not possible?

By the way, I think that of all camera-downloaders I tried (and I think I tried everyone) cam2pc is the one with the best user-interface and moreover the bestlooking. Because of the 2 faults (no real lossless rotation and not updating the exif-rotation tag) I couldn't really use it yet, but when those are gone I will definitely change to cam2pc (from cam4you, JFYI).

greetings
airflow

[nabocorp]

A JPEG image is made of blocks of pixels. These blocks are very oftenly 8x8 but they can be 8x16, 16x8 or 16x16. Most cameras do use 8x8 blocks. A JPEG image can be losslessly rotated only if its dimensions are mutiple of the block size:
- image width must be multiple of the block width
- image height must be multiple of the block height

This is the case for EVERY piece of software. I presume some software just do not tell you anything when they can't losslessly rotate a picture and just perform a lossy rotation.

You can ask the experts this is really the way it is!

Most cameras use 8x8 blocks and the image sizes they use (640x480, 800x600, 1024x768, 1280x960...) all allow lossless rotations.

Best regards,
nabocorp