2007.07.12 15:21 "[Tiff] how to rotate an image", by Oliver Geisen

2007.07.14 13:47 "Re: [Tiff] how to rotate an image", by Andy Cave

Hi Oliver,

We don't specially advertise it... but we have a commercial library that can do this that we can license you. We use this library in FirstPROOF to do our own rotation and have already licensed it to another company. The library is highly optimised and can easily do what you want. It can easily rotate images that are 100,000+ by 100,000+ pixels, so would eat your small ones for breakfast. I doubt you'd find a faster (more optimised) solution. Since we license this library, I'm afraid that how it works (so fast) is not something I can share.

The interface to the library is pretty simple - you supply the input data (band by band) and we then pass you the output data (band by band). You also get an open/close call for the input and output images (and a few other bit-n-bobs). So you can use it for TIFF or any other format.

That's my tip of the day. Contact me off line if you're interested.

Otherwise I suggest you use the rotate code from Richard (in tiffcrop) - although I don't know how fast it'll be on your sized images - that would be something you'd have to try to see if it's fast enough for what you want.



----- Original Message -----

How large are the images you're rotating? Our pre-press product

> FirstPROOF has the ability to rotate 1-bit images, by 90, 180 or 270 > degrees, very fast, however big they

The images are 16300x27501 pixels, bilevel, which makes them abount 48MB of size (unpacked).

I can force images to be stripped or tiled. For now i use striped.

> are, whether they are striped or tiled. I can tell you that writing such > code to be efficient for any sized images (and leaving a resulting image

> that is sequentially accessed on disk for subsequent maximum i/o > performance) is not a trivial task. If you're not an experienced s/w

> engineer, I would suggest you hire one.

I think you are right, but i want to know how to do that :-) I would not title myself as an experienced s/w engineer, but i would be very pleased to learn from one...

So could you give me some tips how to do rotation/bit shifting very fast?