Specifying number of colors in pdf to tiff conversion

[Valentina]

I am converting a multi-page pdf to multi-page tiff. The input pdf size is 229 KB and the output tiff size is 3.7 MB, even after using the LZW compression. The image information told me that the number of colors is 24 million (24 bits/pixel), so I guess nconvert kept the number of original colors. Then I tried to experiment with the "colours num" parameter, but this only reduced the size to 1.3 MB. The number of colors reported this time was 16 (4 bits/pixel). Please tell me whether the following is the right command to use:

nconvert -out tiff -colours 2 -c 2 -o D:\Temp\output.tif -multi D:\Temp\input.pdf

Eventually I want to have only 2 colors, because the pdf contains scanned word documents.

Thank you!

Valentina

[xnview]

nconvert -out tiff -colours 2 -c 2 -o D:\Temp\output.tif -multi D:\Temp\input.pdf
Eventually I want to have only 2 colors, because the pdf contains scanned word documents.

Yes, you can use this line, and use G3/G4 compression for tiff output (-c 4 or -c 6).
Regards. Pierre.

[Valentina]

Pierre,

Thank you for your input. I tried both settings and the size did decrease a bit, but the number of colors remained 16 (4 bits/pixel). Here are the combinations I tried:

nconvert -out tiff -colours 2 -c 2 -o D:\Temp\output.tif -multi D:\temp\45.pdf
nconvert -out tiff -colours 2 -c 4 -o D:\Temp\output.tif -multi D:\temp\45.pdf
nconvert -out tiff -c 2 -o D:\Temp\output.tif -multi D:\temp\45.pdf
nconvert -out tiff -c 4 -o D:\Temp\output.tif -multi D:\temp\45.pdf

Also, I've noticed that in some pages the quality is considerably lower. Setting up "-dpi 300" or "-dpi 600" did not result in higher quality. Could it be that the dpi parameter doesn't apply to the pdf to tiff conversion or maybe the number of colors should not be restricted?

Sincerely,
Valentina

[Guest]

Valentina sei italiana e stai cercando sistemi per la trasmissione fax?
Se si mandami una mail a questo indirizzo:
_archimede_@libero.it
Grazie

[Strasser_a]

I have also a problem with the conversion pdf -> tiff. But what i figured out is, that when i do the conversion with xnview and "convert" the picture to black/white (even if there are only two colors) and create than a tiff output the size and the contents of the tiff are correct. Otherwise it seems that (even if i take the tiff-G4 output) there are the color information included in the tiff.

Is there a way to do it also with nconvert ?

Axel

[xnview]

I have also a problem with the conversion pdf -> tiff. But what i figured out is, that when i do the conversion with xnview and "convert" the picture to black/white (even if there are only two colors) and create than a tiff output the size and the contents of the tiff are correct. Otherwise it seems that (even if i take the tiff-G4 output) there are the color information included in the tiff.

Is there a way to do it also with nconvert ?

Axel

I add soon a method to convert in true black&white.
Pierre.