Determine color info for pages 1

[cheyney]

I am wondering if there is a way to determine what pages of a postscript contain color information and what pages contain only black&white/grayscale.

I am assuming I will have to use a postscript interpreter like ghostscript, but I don't know where to start.

Any help would be greatly appreciated,

Cheyney

 

[tgreer]

Cheyney,

This is so nearly impossible it's best to give up now. Without rasterizing the file and looking at each pixel, there really isn't a good way to do this.

You can't just do a keyword search, for example for "setcmykcolor". Many PostScript drivers and applications define all sorts of colorspaces and operators even if they never use them.

Then too, you have to check not just operators but parameters. Is .5 .5 .5 setrgbcolor a color? Or a shade of gray?

Then you have device-independent colorspaces, LAB colors and CIE, /DeviceN colors and Spot Colors. Are you going to maintain a lookup table of all Pantone Colors? Are all Pantone grays really grays?

You begin I hope to see the problem.

If you have some control over the PostScript (for example, you're only looking at output from a single application on a stable platform with a driver that doesn't change), then you can slowly whittle away at this.

Good luck!

Thomas D. Greer

 

[cheyney]

ugh, ok thanks

I kindof expected that much...

The application I'm developing has a certain degree of human interaction for each file, so I'll probably do what you said and rasterize the postscript into a series of suitably-high resolution bitmaps and then look at the pixels to determine if there's any color in the file. Less than perfect, I know, but its quick and easy to implement and probably good enough. The process currenly produces jpegs for each postscript anyway. all I need is a quick little c program that looks at the color info for each pixel.

Thanks for your help, you've probably saved me more than a couple hours of research.

Cheyney

 

[tgreer]

My pleasure.

 

[alexcher]

Don't forgget that the color vs. black-and-white property depends on the CDR installed on the device. You need to copy CRD;s from your target inteerpreter to Ghostscript before rasterizing.

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