PNG colorspace conversion

[Guest]

How can I convert PNG images so they have a colorspace of /DeviceGray not /DeviceRGB? I have tried in both fireworks and photoshop but neither appear to give a true /DeviceGray setcolorspace instead they give a /DeviceRGB setcolorspace

This are read by our XEROX color printer as a color document and costs 10 times the amount to the business.

[Helge_Blischke]

In case you are using CUPS as your printing system, see

http://sourceforge.net/projects/cupsaddons/files/filter-colorfilter/

for a filter that converts e.g. /DeviceRGB to /DeviceGray if the

R, G, and B components are nearly equal.

As the filter is written in Perl, it is quite easy to modify it to function

as a standalone utility.

Helge

[Dov Isaacs]

I don't know what version of Photoshop you are using, but it certainly is possible to create a true grayscale PNG file without a profile. Just did so in a few seconds.

          - Dov

[Guest]

Dov,

I've tried a couple of times in Photoshop CS5 but when the images are added to the PS file they still show as RGB not Gray.

Anymore information or help to acheive true grayscale is appreciated.

Regards,

Mark

[Test Screen Name]

How did you get the PNG into the PostScript file?

[Guest]

Its a third party software that builds PostScript file.

[Test Screen Name]

Then you need to look at this code. It is normal and typical for image to PS generators to use RGB as their default, and if it prints through GDI it may actually have no choice.

[Guest]

Its only the pngs I'm having problems with. All other images (jpg, gif, tiff) covert and show as /DeviceGray but no matter what I do to the png tey still show as RGB

[Test Screen Name]

Then it is with the makers of that software with whom you need to speak.

[Guest]

Thanks for your help but hopefully Dov will get back to me with more information regarding PNG conversion to true grayscale using CS5.

[Dov Isaacs]

Mark,

I don't know exactly what you are doing with Photoshop or the “third party software that builds PostScript file” that you mention below, but the fact is that Photoshop fully supports grayscale PNG in terms of creation, opening, manipulating, and output of same back to PNG as well as to PostScript PDF. The only way you can get a conversion of color space is if you explicitly request such a change.

          - Dov