[Gimp-developer] Saving black/white TIFF with 'CCITT Group 4' encoding

[Manfred Joerg]

Hello Sven,

I just checked your revised tiff patch. 

1. It doesn't allow the user to save a rgb image as CCITT Datagroup 3/4 even 
if it contains only black and white pixels. Instead the user has to convert 
the image to indexed mode black/white first. For my sample image (4048 x 6648 
pixels) that takes 50 seconds on a Pentium IV 3 GHz machine (no colour 
dithering). 

There are three ways to improve this:
- Allow the user to save images of all modes as CCITT. The tiff library can 
handle this if the image contains only black and white pixels. Otherwise the 
tiff library returns an error code.
- Improve the speed of the conversion to indexed mode.
- Add an option to the threshold tool which automatically creates an indexed 
black white image


2. The tiff files created by the Gimp are 4% greater than the ones created by 
Irfanview. Are you using the latest version of the tiff library? However it's 
not so bad. The tiff files generated by XnView are 13% greater.


Apart from that the patch works fine. I checked it under Windows. I saved some 
files and opened them with Irfanview and XnView.


Regards
Manfred


On Thursday 01 February 2007 09:34, Sven Neumann wrote:
> Hi,
> I've attached a revised patch some days ago. Did you (or anyone else)
> get a chance to try it? I would like to commit this as soon as possible
> but the patch needs some more testing before it can go in.
>
>
> Sven