AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

2007.07.12 15:21 "[Tiff] how to rotate an image", by Oliver Geisen
2007.07.12 15:30 "Re: [Tiff] how to rotate an image", by Andy Cave
2007.07.14 12:45 "Re: [Tiff] how to rotate an image", by Oliver Geisen
2007.07.14 13:47 "Re: [Tiff] how to rotate an image", by Andy Cave
2007.07.13 16:19 "[Tiff] Re: Bit shifting and rotating of TIFF images", by Richard Nolde
2007.07.14 12:39 "Re: [Tiff] Re: Bit shifting and rotating of TIFF images", by Oliver Geisen
2007.07.14 16:03 "Re: [Tiff] Re: Bit shifting and rotating of TIFF images", by Bob Friesenhahn
2007.07.16 04:57 "[Tiff] Image Roation by 180 degrees", by Richard Nolde
2007.07.18 00:33 "Re: [Tiff] Re: Bit shifting and rotating of TIFF images", by Chris Cox
2007.07.17 09:32 "Re: [Tiff] Re: Bit shifting and rotating of TIFF images", by Oliver Geisen
2007.07.17 12:10 "Re: [Tiff] Re: Bit shifting and rotating of TIFF images", by Ron
2007.07.20 04:26 "[Tiff] Bit shifts vs lookup tables", by Richard Nolde

2007.07.17 09:32 "Re: [Tiff] Re: Bit shifting and rotating of TIFF images", by Oliver Geisen

Hello Bob,

Simulated image of 16300x27501 pixels, bilevel:

Results:

* plain reading/writing (no bit-manipulation): 0.294 sec
 using bit-shift operator ("<<" resp. ">>"):  1.920 sec *
 using lookup-table:                          0.380 sec*

>
> That is interesting. It seems that you are right that for the CPU

> you are using the lookup-table approach is much faster. Maybe it > is always faster.

I think this is true for images beyond a specific size (number of pixels).

>> How could an algorithm be faster?
> I am not sure.

When working with large images, i don't think any algorithm could beat this.

>> How is it done in assembler (my asm-knowledge is a bit rusty. It >> ends with Z80, which is about 20 years ago)?

> Sorry, I stopped with the 8085 myself. Over 20 years ago. :-) Okay, i think i'll stay at lookup-tables, because it's makes the best effort for me.

Oliver Geisen
Systemadministrator
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